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Thesis_3_10

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Thesis_3_10

  1. 1. i AACCKKNNOOWWLLEEDDGGEEMMEENNTTSS I would first like to thank God for making this all possible. I also owe a debt of gratitude to DDrr.. AAhhmmeedd RRaagghheebb, for his encouragement and help with this project. Another debt of gratitude is also due to DDrr.. KKhhaalleedd SShhaawwkkii, who was patient, helping and encouraging throughout the writing. I must also thank DDrr.. WWaaeell KKaammeell and DDrr.. HHeesshhaamm BBaassssiioouunnyy for their instructions. Finally, without the love and support of my parents, and the rest of my family, I could not have survived the first semester of graduate school, much less conducted this research.
  2. 2. ii AABBSSTTRRAACCTT Earthmoving operations are often among the most vital operations in many construction projects owing to their significant effect on the project cost and duration. A trade-off between the highest production rate and the lowest cost of earthmoving operations is most desirable. Therefore, it would be advantageous to develop a tool to assist the managers of such projects in the decision making process. A Decision Support Tool (PROEQUIP) utilizing simulation has been developed in this research to assist in the selection of the appropriate earthmoving combination of the hauling and excavating units. PROEQUIP can also predict and help in monitoring the production rate and cost of earthmoving operations. Unlike most previous methods and techniques which have been devised to simulate either production rate or cost, PROEQUIP can simultaneously simulate the production rate and cost of earthmoving operation using any available combination of equipment, hauled material and road characteristics. PROEQUIP comprises an expandable database and two calculation modules. The database contains the empty weight, maximum payload, loaded truck speed, horsepower and heaped capacity for 27 types of trucks. Weight and filling factor characteristics of 23 materials as well as the rolling resistance of 21 road materials are also stored in the database. The two modules included into PROEQUIP can retrieve any data needed from this database. The first of these two is a deterministic performance module which uses commonplace empirical relationships to calculate the cost and production rate for a specific combination of road and excavation material, and truck and excavator specifications. The second module uses the simulation technique to predict the cost and production rate for a number of possible combinations of truck/excavator systems. PROEQUIP was validated using data collected from an earthmoving project in Egypt and another in Saudi Arabia. The actual production rates were estimated at the lower 7th and 28th percentile of the results simulated by PROEQUIP, respectively.
  3. 3. iii TTAABBLLEE OOFF CCOONNTTEENNTTSS ACKNOWLEDGEMENTS............................................................................. i ABSTRACT………………………………………………………………….ii LIST OF FIGURES ........................................................................................ v LIST OF TABLES .........................................................................................ix LIST OF SYMBOLS......................................................................................xi CHAPTER 1: GENERAL INTRODUCTION............................................. 1 1.1 INTRODUCTION........................................................................................2 1.2 RESEARCH AIM AND OBJECTIVES ......................................................3 1.3 ORGANIZATION OF THE RESEARCH...................................................4 1.4RESEARCHSCOPE AND LIMITATIONS .................................................5 1.5LAYOUT ANDMETHODOLOGY OF PROEQUIP ...................................6 CHAPTER 2: REVIEW OF LITERATURE............................................... 8 2.1 INTRODUCTION........................................................................................9 2.2 GENERAL REVIEW...................................................................................9 2.3COMPUTERS IN EARTHMOVING .........................................................12 CHAPTER 3: EARTHMOVING OPERATIONS..................................... 21 3.1 INTRODUCTION......................................................................................22 3.2 MANAGING EARTHMOVING OPERATIONS .....................................22 3.2.1 Safety...................................................................................................23 3.3HYDRAULIC EXCAVATORS..................................................................26 3.4 TRUCKS AND HAULING OPERATIONS .............................................30 CHAPTER 4: ESTIMATING TECHNIQUES.......................................... 34 4.1 INTRODUCTION......................................................................................35 4.2 PRODUCTIVITY ESTIMATING .............................................................36 4.3 COST ESTIMATING ................................................................................50 4.3.1 Fixed Costs ..........................................................................................52 4.3.2 Operating Costs ...................................................................................54 4.3.3 Labor Costs..........................................................................................58 4.4 SELECTING THE OPTIMUM EQUATION TO CALCULATE TRUCK SPEED ........................................................................................58
  4. 4. iv CHAPTER 5: DECISION SUPPORT TOOL FOR EARTHMOVING PROJECTS......................................................................... 61 5.1 INTRODUCTION......................................................................................62 5.2 INPUTS, OUTPUTS AND DATABASE..................................................63 5.3 SYSTEM STRUCTURE............................................................................69 5.3.1 System Calculation..............................................................................69 5.3.2 The Simulation ....................................................................................74 5.4 USER INTERFACE...................................................................................79 5.5 THE RESULTS..........................................................................................85 5.6 EXAMPLES FOR TRADITIONAL CALCULATION USING PROEQUIP (PROEQUIP VERIFICATION) ...........................................92 5.6.1 Example 1............................................................................................92 5.6.2 Example 2............................................................................................99 5.7 THE SIMULATION RESULTS ACCURACY:......................................104 5.8 APPLICATION OF PROEQUIP ON REAL CASES: ............................105 CHAPTER 6: CONCLUSION AND RECOMMENDATIONS............. 125 6.1 SUMMARY AND CONCLUSION.........................................................126 6.2 RECOMMENDATIONS FOR FUTURE RESEARCHE........................128 REFERENCES............................................................................................ 130 APPENDICES.. ........................................................................................... 135 Appendix A.....................................................................................................136 Appendix B.....................................................................................................146 Appendix C.....................................................................................................149 Appendix D.....................................................................................................151 Appendix E.....................................................................................................154 Appendix F .....................................................................................................156
  5. 5. v LLIISSTT OOFF FFIIGGUURREESS List of Figures Page Figure 1.1 PROEQUIP results summary ……………………………… 7 Figure 2.1 A Graphical Model for Maximizing Production of a Pushed Scraper ……………………………………………………... 10 Figure 3.1 Hydraulic hoe loading a truck ……………………………... 28 Figure 3.2 Wheel-mounted hydraulic hoe …………………………….. 28 Figure 3.3 Basic parts of a hydraulic hoe ……………………………... 28 Figure 3.4 Hydraulic hoe bucket capacity rating dimensions ………… 28 Figure 3.5 Maximize production of the earthmoving system ………… 29 Figure 3.6 Truck tractor unit towing ………………………………….. 31 Figure 3.7 Off-highway truck …………………………………………. 31 Figure 3.8 Highway rigid-frame rear-dump truck …………………….. 32 Figure 3.9 An articulated dump truck …………………………………. 32 Figure 3.10 An articulated dump truck moving through soft ground ….. 32 Figure 3.11 Off-highway tractor towing a loaded bottom-dump trailer .. 32 Figure 3.12 Highway bottom-dump ……………………………………. 32 Figure 3.13 Measurement of volumetric capacity …………………….... 33 Figure 4.1 Material-Volume Changes Caused by Construction Processes …………………………………………………... 36 Figure 4.2 Performance chart for Caterpillar 793C Truck ……………. 47 Figure 4.3 Basic truck load cycle ……………………………………… 48 Figure 4.4 Equipment Cost Model …………………………………….. 51 Figure 5.1 Soil properties database figure …………………………… 65 Figure 5.2 Road condition database figure ………………………….. 66 Figure 5.3 Trucks form to add, edit and delete truck …………………. 67 Figure 5.4 Trucks form to search for existing truck …………………... 67 Figure 5.5 User interface parameters flowchart ………………………. 68 Figure 5.6 Production calculation flowchart for earthmoving system .. 70
  6. 6. vi LLIISSTT OOFF FFIIGGUURREESS ((CCoonntt’’dd)) List of Figures Page Figure 5.7 Unit cost calculation flowchart for earthmoving system …...... 71 Figure 5.8 Simulation model network diagram for the activities ……….. 77 Figure 5.9 Normal probability distribution for the random variables ….. 77 Figure 5.10 Beta probability distribution for the random variables ……… 77 Figure 5.11 The simulation model pseudocode …………………………... 78 Figure 5.12 User interface – Project information ………………………… 79 Figure 5.13 User interface – Job information ……………………………... 80 Figure 5.15 User interface – Haul road information ……………………… 81 Figure 5.15 User interface – Equipment selection section ……………….. 82 Figure 5.16 User interface – Equipment Unit Cost section ………………. 83 Figure 5.17 User interface – Equipment Cost section ……………………. 83 Figure 5.18 User interface – Simulation section ………………………….. 84 Figure 5.19 The production and cost results page ………………………… 85 Figure 5.20 The results data sheet page …………………………………... 86 Figure 5.21 The simulation calculations interface – trials section A …….. 88 Figure 5.22 The simulation calculations interface – trials section B …….. 88 Figure 5.23 The simulation calculations interface – trials section C …….. 88 Figure 5.24 The simulation results – unit cost ……………………………. 89 Figure 5.25 The simulation results – Production …………………………. 89 Figure 5.26 The overlay charts for productivity and cost ……………….... 90 Figure 5.27 The recommendations (advices) page ……………………….. 91 Figure 5.28 Safety video sample in the recommendations ……………….. 91 Figure 5.29 Caterpillar 725 Articulated Truck specifications ……………. 93 Figure 5.30 The results of example 1 in the Results page ………………… 98 Figure 5.31 Caterpillar 725 Articulated Truck specifications ……………. 99
  7. 7. vii LLIISSTT OOFF FFIIGGUURREESS ((CCoonntt’’dd)) List of Figures Page Figure 5.32 The results of example 2 in the Results page ………………… 103 Figure 5.33 GAZADCO project (site plan) ……………………………….. 106 Figure 5.34 GAZADCO project (shrimp pond works) …………………… 107 Figure 5.35 GAZADCO project (Earthmoving works) …………………… 107 Figure 5.36 GAZADCO project (Excavation works A) …………………... 108 Figure 5.37 GAZADCO project (excavation works B) …………………… 108 Figure 5.38 GAZADCO project (excavation works C) …………………… 109 Figure 5.39 GAZADCO project - Mercedes Benz 3328K (1987) ………... 111 Figure 5.40 GAZADCO project - Mercedes Benz 2638 (1993) ………….. 111 Figure 5.41 GAZADCO project - Mercedes Benz 2635 (1991) ………….. 111 Figure 5.42 GAZADCO project - Volvo – FM12.420 (2004) ……………. 111 Figure 5.43 GAZADCO project - Mercedes Benz 2628(1983) ………….. 111 Figure 5.44 GAZADCO project - Hyundai R140 LC – 7 ………………… 111 Figure 5.45 GAZADCO project - Caterpillar 325 DL ……………………. 112 Figure 5.46 GAZADCO project - Mercedes Benz 4143 (2003) ………….. 112 Figure 5.47 GAZADCO project - Mercedes Benz 4037 (1997) ………….. 112 Figure 5.48 GAZADCO project - Kumatsu PC240 LC …………………... 112 Figure 5.49 GAZADCO project - Caterpillar 225 ………………………... 112 Figure 5.50 The productivity distribution for the first case ………………. 113 Figure 5.51 The simulation overlay charts for all study cases ……………. 114 Figure 5.52 The suggesting optimum cases to be selected …………….…. 115 Figure 5.53 NILE COMPANY project (site works) ……………………… 118 Figure 5.54 NILE COMPANY project - Mercedes Benz 3331 …………... 119 Figure 5.55 NILE COMPANY project - Scania 113H …………………… 119 Figure 5.56 Kumatsu PW160 ……………………………………………... 119
  8. 8. viii LLIISSTT OOFF FFIIGGUURREESS ((CCoonntt’’dd)) List of Figures Page Figure 5.57 Kumatsu PC210 LC …………………………………………. 119 Figure 5.58 The productivity distribution for the first case ……………. 120 Figure 5.59 The simulation overlay charts for all study cases …………… 121 Figure 5.60 The suggesting optimum cases to be selected ….……….…. 122 Figure 5.61 The simulation overlay - probability - charts for all study cases …………………………………………………………. 124 Figure 6.1 The organization of the research ……………………………. 126
  9. 9. ix LLIISSTT OOFF TTAABBLLEESS List of Tables Page Table 2.1 PROEQUIP and previous published models for earthmoving 18 Table 4.1 Material Volume Conversion Factors ………………………... 37 Table 4.2 Loading excavator cycle times for a 90o swing (seconds) …... 39 Table 4.3 Excavator swing factors ……………………………………… 41 Table 4.4 Weight of Materials according to German Norm DIN/VOB ... 41 Table 4.5 Typical rolling resistance factors …………………………….. 44 Table 4.6 Operator Skill Factor, FO........................................................... 45 Table 4.7 Job Efficiency Factor, Fe……………………………………... 45 Table 4.8 Excavator operating efficiency ……………………………… 45 Table 4.9 Selecting ownership period based on operating conditions… 53 Table 4.10 Maintenance and repair rates as a percentage of the hourly depreciation for selected equipment ………………………… 55 Table 4.11 Weights, fuel consumption rates, and load factors for diesel and gasoline engines …………………………………………. 56 Table 4.12 Guidelines for tire life for off-highway equipment ………….. 57 Table 4.13 Summary of example 1 …...………………………………… 59 Table 4.14 Summary of example 2 …….……………………………….. 60 Table 5.1 Parameters for the Random Variables Used in the Models … 76 Table 5.2 User Interface – Window 1 description …………………….. 79 Table 5.3 User Interface – Window 2 description ……………………. 80 Table 5.4 User Interface – Window 3 description ……………………. 81 Table 5.5 User Interface – Window 4 description ……………………... 82 Table 5.6 User Interface – Windows5 and 6description ……………... 84 Table 5.7 User Interface – Window 7 description …………………….. 84 Table 5.8 The results of example 1 using PROEQUIP software ……… 98 Table 5.9 The results of example 2 using PROEQUIP software ……… 103 Table 5.10 The production results according to number of trials change 104
  10. 10. x LLIISSTT OOFF TTAABBLLEESS ((CCoonntt’’dd)) List of Tables Page Table 5.11 GAZADCO Project data and description ………..………….. 105 Table 5.12 GAZADCO Project Company Equipment (Trucks) ………... 109 Table 5.13 GAZADCO Project Company Equipment (Excavators) ……. 110 Table 5.14 GAZADCO Project Equipment available for renting (Trucks) ……………………………………………………... 110 Table 5.15 GAZADCO Project Equipment available for renting (Excavators) …………………………………………………. 110 Table 5.16 Kabary-Matrooh Project data and description ……………… 117 Table 5.17 Kabary-Matrooh Project Company Equipment (Trucks) ....... 118 Table 5.18 Kabary-Matrooh Project Equipment for renting (Excavators) 119
  11. 11. xi LLIISSTT OOFF SSYYMMBBOOLLSS SYMBOLS NOMENCLATURES UNIT  Average material density ton/m3 A Equipment Availability factor AS:D Angle of swing and depth (height) of cut correction B Bucket capacity m3 Bc Nominal bucket capacity m3 BCM Bank Cubic Meter m3 Bf Bucket fill factor C Theoretical cycles/hr for a 90o swing cycles/hr c2, c3 Rolling resistance constant Cbe Bucket heaped capacity m3 CCM Compacted Cubic Meter m3 CECE The Committee on European Construction Equipment Cht Truck heaped capacity m3 CIPROS knowledge based construction planning simulation system cr Rolling coefficient CYCLONE Cyclic Operations Network Di Distance from haul to dump site km D Equipment depreciation per hour LE/hr Dd Number of working days per week day Dh Number of working hours per day hour DISCO Graphical simulation modeling for bridge construction E Equipment efficiency
  12. 12. xii LLIISSTT OOFF SSYYMMBBOOLLSS ((CCoonntt’’dd)) SYMBOLS NOMENCLATURES UNIT e Engine efficiency ESEMPS Expert system using for road equipment F Fuel cost per hour LE/hr ff Bucket fill factor Fl Fuel cost per liter LE Ft Tractive force N GHP The gross engine horsepower at governed engine rpm hp GMW Gross machine weight kg GR Road Grade resistance N GPSS General Purpose Simulation System h Helper cost per hour LE/hr hp Equipment engine horse power hp hpt Truck engine net power hp HSM The Hierarchical Simulation Model I Interest cost per hour LE/hr i Interest rate % IS Insurance cost per hour LE/hr is Insurance rate % K The weight of fuel used per brake hp/hour kg/br.hp-hr KPL The weight of fuel kg/liter L Labor cost per hour LE/hr LCM Loose Cubic Meter m3 LF The load factor LMPH The liters used per machine hour liter
  13. 13. xiii LLIISSTT OOFF SSYYMMBBOOLLSS ((CCoonntt’’dd)) SYMBOLS NOMENCLATURES UNIT Lt Rated truck load ton M Maintenance and repair cost per hour LE/hr m Vehicle mass kg MicroCYCLONE Cyclic Operations Network using microcomputers Mta Mass on tractive Rear axle kg Nb Number of excavator buckets bucket Nh Number of helpers Helper Nt Number of trucks truck O Job operational factor OA Equipment Operating Efficiency Pe Energy power kW P Production m3 /hr PCSA Power Crane and Shovel Association Pt Truck payload kg PTF Propel time factor kg Q heaped bucket capacity m3 Qs Excavator productivity m3 /hr Qt Truck productivity m3 /hr Rr Road Rolling resistance N Rt Road Total resistance N S Salvage value LE s Slope of haul road % Sf Swing factor SAE Society of Automotive Engineers SIMPHONY Special purpose construction simulation model
  14. 14. xiv LLIISSTT OOFF SSYYMMBBOOLLSS ((CCoonntt’’dd)) SYMBOLS NOMENCLATURES UNIT SPS Special Purpose Simulation STROBOSCOPE State and Resource-Based Simulation of Construction Processes te Excavator cycle time Sec T Taxes cost per hour LE/hour t Taxes rate % tc Excavator cycle time for a 90o swing min. TC Total unit cost per hour LE/hour Tcc Tire change (replacement) cost LE tce Excavator cycle time sec. Tct Total truck cycle time min. tct Truck cycle time min. td Dump time min. th Haul time min. Tic Tire cost per hour LE/hour tL Load time min. tr Approximate tire life hours tr Return time min. TR Total resistance N U Lubricant cost per hour LE/hour UM-CYCLONE Cyclic Operations Network under DOS system V Truck speed km/hr VC volume correction for loose volume to bank volume VH Velocity of haul direction km/hr Vhe Truck speed empty km/hr Vhl Truck speed loaded km/hr
  15. 15. xv LLIISSTT OOFF SSYYMMBBOOLLSS ((CCoonntt’’dd)) SYMBOLS NOMENCLATURES UNIT Vl Load volume m3 Wet Truck empty weight kg Wf Weight fully loaded ton Wgt Gross weight of the truck kg Wl Load weight kg Ws Weight of soil kg/ m3 η Transmission efficiency μ Coefficient of friction
  16. 16. CCHHAAPPTTEERR OONNEE GGEENNEERRAALL IINNTTRROODDUUCCTTIIOONN
  17. 17. 2 CCHHAAPPTTEERR 11 GGEENNEERRAALL IINNTTRROODDUUCCTTIIOONN 11..11 IINNTTRROODDUUCCTTIIOONN Construction is an important industry in terms of the annual capital invested in construction work and its high employment. The importance of the industry can also be measured by its contribution to the gross national product. However, the construction industry is in a difficult position due to the decline in construction productivity which started in the mid 1970's [1]. The current stringent financial situation aggravates these difficulties. Facing these challenging problems, the construction industry became aware of the importance of productivity improvement and cost reduction, and is striving for such improvements. Historically, productivity improvement was often focused on labor effort; this also applied to the construction industry. But there is a second important term in production improvement especially in construction industry which is the earthmoving equipment [1]. Earthmoving may include site preparation, excavation, embankment construction, backfilling, dredging, preparing base course, subbase, subgrade, compaction, and road surfacing. The types of equipment used and the environmental conditions will affect the man- machine-hours required to complete a given amount of work. Before preparing estimates, there is a need to select the best method of operation and the type of equipment to use. Each piece of equipment is specifically designed to perform certain mechanical tasks. Therefore, the equipment selection should be based on efficient operation and availability. Earthmoving is characterized by the intensive utilization of machines. It is therefore often one of the most important operations in many construction projects in terms of its cost and productivity.
  18. 18. 3 Hence, earthmoving planning is a potential area for further productivity improvement. To improve earthmoving planning, a variety of methods and techniques has been tried. The rapid development of computer technology provides a useful means to assist in construction management and planning. Proper equipment selection is crucial to achieve efficient earthmoving and construction operations. The machine‘s operational capabilities and equipment availability should be considered when selecting this machine for a particular task. The manager should visualize how best to employ the available equipment based on soil considerations, zone of operation, and project-specific requirements. Cost and productivity estimates, productivity control, and production records are the basis for management decisions. Therefore, it is helpful to have a common method of recording, directing, and reporting production. 11..22 RREESSEEAARRCCHH AAIIMM AANNDD OOBBJJEECCTTIIVVEESS This research addresses the development of a decision supporting tool which could be used for the selection of appropriate earthmoving equipment and for the estimation of their productivity and cost. Furthermore, provide some important safety recommendations for using earthmoving operations are later provided. The overall aim of this research is to develop a simulation model in the form of computer application to assist managers to manage and estimate the productivity, duration and cost of earthmoving system. In order to attain the above aim, four specific objectives will have to be achieved: 1) Collection of data needed to compile required databases of:  Equipment database: provide truck empty weight, truck payload, truck horsepower, top loaded speed of the truck and truck heaped capacity  Excavated material database: provide material weight, bucket fill factor and excavator cycle time based on material type.
  19. 19. 4  Rolling resistance database based on haul road type. 2) Design a mathematical model to perform the calculations necessary to estimate productivity rate, cost and duration for a given earthmoving system to be used for monitoring, control and improvement of ongoing operations. 3) Obtain performance data for as many earthmoving systems as possible to be used in the simulation. 4) Design a simulation model integrated with a mathematical model to enable the comparison among presented earthmoving systems. 11..33 OORRGGAANNIIZZAATTIIOONN OOFF TTHHEE RREESSEEAARRCCHH The remainder of this research is organized as follows: Chapter 2 covers a literature survey. The goal of this chapter is to present a comprehensive review of the previous efforts on improving earthmoving project performance, especially earthmoving equipment planning and selection using a mathematical model or simulation. Chapter 3 presents general information about two major earthmoving equipments: trucks and excavators. This information can help in the selection of appropriate equipment for particular earthmoving operations under certain working conditions. Earthmoving equipment productivity and cost are the major parameters in the selection of appropriate machines for earthmoving operations. Chapter 4 discusses the productivity and cost estimating of earthmoving equipment and factors influencing productivity. Chapter 5addressesthe decision support tool (PROEQUIP) and explains the component of this application and its database. The application user interface data and the source of those data are presented. Finally, Conclusions and Recommendations for further research development are presented in Chapter 6.
  20. 20. 5 Appendices include a list of selected visual basic programming codes, excavator cycle time estimating method, unit cost calculation form and Excel formulas which have been used in the simulation model. 11..44 RREESSEEAARRCCHHSSCCOOPPEE AANNDD LLIIMMIITTAATTIIOONNSS Earthmoving equipment planning and management deals with a wide range of issues, including equipment financing, standardization, maintenance scheduling, replacement schemes, safety and routine operational planning. The focus of this research is on: 1. The operational planning, particularly on the development of a computer decision support tool which could be used for the selection of appropriate earthmoving equipment to complete a given job 2. The estimation of the cost and duration of the job In earthmoving operations, earthworks may include loosening, excavating, loading, hauling, unloading, placing, spreading, grading, and compacting. For simplicity of the tool, this research deals only with four phases: excavating, loading, hauling and unloading. The main outcome of this research is an interactive advisory decision support tool for equipment selection which facilitates the comparison among the performances of different earthmoving systems working under specified jobsite conditions according to the following points: 1) The parameters that may affect equipment performance are described in Chapter 3. However, the measurement of these parameters in the field was not conducted. 2) It is assumed that the operator will always operate the truck at a constant speed regardless of any acceleration and deceleration. In reality, however, the operator will not operate the machine at maximum performance
  21. 21. 6 throughout the haul segment and it might be possible that the operator never operates the machine at maximum performance in a certain segment. 3) Earthmoving system production and unit cost is calculated using the estimation technique described in detail in Chapter 4. 4) Not all equipment categories will be modeled (equipment categories describe their general function, or type) and not all classes within each category will be modeled (classes describe the weight, horsepower, or size of equipment within its category);the categories and classes that will be analyzed are machines that are fairly common throughout the industry. The study will be limited to Caterpillar Articulated trucks, Caterpillar excavators and equipment that will be described in the "Cases of Study" section in chapter 5. 5) Travel time will be calculated using the equation based on equipment performance charts contained in the Caterpillar Performance Handbook [1] that will be validated by two examples in chapter 4. 6) This work is also limited in that it will analyze historical data from a relatively small number of companies. This does not necessarily mean that the simulation result represent every firm type, size, geographic region, or management style. Every construction company is unique. The study is limited to the medium size construction industry projects that will be described in the "Cases of Study" section in chapter 5. Mining and huge projects were not being investigated. 7) The tool that will be developed in this research can be used by the contractor, planners, project managers and construction engineers. The study assumptions will be presented in "The Simulation" section in the chapter 5. 11..55 LLAAYYOOUUTT AANNDDMMEETTHHOODDOOLLOOGGYY OOFF PPRROOEEQQUUIIPP A computer application (PROEQUIP) was developed using Microsoft Visual Basic.Net and consists of three interfaces:
  22. 22. 7 1. User Interface: is the one which the user will use to input the required parameters. 2. Calculations and results interface: deals with calculations involved in estimating production and the final results of production, duration and cost and simulation results. The simulation part of this interface will be developed using CRYSTAL BALL as an Excel add-in integrated within PROEQUIP, Figure 1.1. 3. Recommendations Interface: is the location of some important safety recommendations to assist applying safety while using earthmoving system. Figure 1.1 PROEQUIP results summary SIMULATION MODEL •what is the best system to work in this area? •What is the economical equipment combination to finish the required job? •Which site part will be finished first? •What is the best system to finish the job faster? PERFORMANCE ASSESSMENT AND OPTIMIZATION RESULTS •Does the existing equipment combination work fine? •How to manage this job to gain the maximum productivity? •What are number of trucks and buckets required to minimize the system cost? •What are number of trucks and buckets required to provide maximum productivity? •When does this equipment combination finish the required job? •Does this equipment combination can progress the work on time? •Does this equipment combination work as required or the work is behind the schedule? Database
  23. 23. CCHHAAPPTTEERR TTWWOO RREEVVIIEEWW OOFF LLIITTEERRAATTUURREE
  24. 24. 9 CCHHAAPPTTEERR 22 RREEVVIIEEWW OOFF LLIITTEERRAATTUURREE 22..11 IINNTTRROODDUUCCTTIIOONN The literature review in this chapter contains two parts. The first part is an overview of the research development in the area of earthmoving and the methods and techniques used in previous work. The second part presents several models closely associated with earthmoving equipment and deals with computer-aided programs used in earthmoving projects. 22..22 GGEENNEERRAALL RREEVVIIEEWW As the earthmoving planning process is a comprehensive one driven by many factors, the identification of these factors is particularly important. Studies have been conducted on these factors and their treatment. To find the solutions to specific problems in earthmoving, many methods and techniques have been tried. The Caterpillar Tractor Company developed a graphical model in 1968 (see Figure 2.1) for solving the machine matching problem by analyzing machine output. In developing this model, it was found that the load of a scraper increases rapidly, but the loading rate decreases as the scraper capacity is approached as shown by line BDO in Figure 2.1 [1]. In Figure 2.1, the vertical axis indicates the amount of material loaded, and the horizontal axis represents certain parts of the cycle time. Line BDO is a typical load-growth curve for a bottom-loading scraper pushed by a track type tractor. Line AO (2.7 minutes) is the cycle time les the loading time for this particular scraper and soil, line CO (0.3 minutes) is the cycle time less the loading time of the pusher. The slopes of lines connected from points A and C to the load-growth curve BDO indicate the output per unit time of the scraper and loader respectively, and the two
  25. 25. 10 lines would have their steepest slopes (maximum output per unit time) if they were drawn tangential to the load-growth curve. In each case, the optimum loads are determined to be about 31 and 23 cubic meters with pushing time being 0.8 and 0.35 minutes respectively. If the pusher works with two or more scrapers, this model can determine the most optimum production of the fleet when the costs of the pusher and scrapers are considered [1]. Figure 2.1 A Graphical Model for Maximizing Production of a Pushed Scraper In 1968, Griffis issued a paper on Queuing Theory and optimizing haul fleet size. The main components of Queuing system are interiors (customers) and service suppliers. When a customer refers to a system for receiving service, two different cases may happen. If one of the service suppliers is free, then giving the service to the customer begins immediately. On the other hand if all service suppliers are busy, then the customers should wait and thus the queue will be made. In the truck filling and refilling problem, the trucks are assumed as the customers of Queuing system. Loaders are known as service providers in this system. One loader along with specified number of trucks is known as a Queuing system. The objective of solving this problem is to determine the number of loaders and trucks in a manner to
  26. 26. 11 increase the probability of truck existence for one loader as much as possible. In other words, by allocating appropriate number of trucks the loader will be always busy [2]. In earthmoving operations, it is common for different types of machines to work together to complete a job task. For instance, a Loader-truck fleet is often used to move earth. Gates and Scarpa pointed out that a trade-off should be made between a lesser number of large and expensive hauling units and a greater number of small and relatively inexpensive hauling units [3]. Later, Gates and Scarpa carried out research into the factors that affect the selection of earthmoving equipment and summarized these factors into four categories [4]: 1) Spatial Relationships: In this category, the major factors were identified to be the elevation of the working platform, the face and level of excavation, obstructions in excavation and the configuration of excavation. 2) Soi1 Characteristics: This category covers the soil's ability to support excavators and hauling units and other soi1 characteristics such as traction, rolling resistance and gradeability. 3) Contract Provisions: The factors in this category include the quantities of excavation, moving, and fill; the allowable time of construction; provisions for payment cash flow. 4) Logistical Considerations: The factors included in this category involve the availability of equipment and operators with applicable experience; the time and cost to mobilize and demobilize crews; the use of equipment in preceding and in subsequent operations (resource leveling); rental costs, ownership costs, operating costs and production rates. In 1989, Karshenas developed a model by applying probability theory to determine the capacity and number of trucks matching the given loaders in a fleet. The solutions of the model were given in several graphical formats. According to the loader capacities, the capacity-number combinations of trucks, which possess a minimum cost of production, can be quickly determined [5].
  27. 27. 12 Heavy vehicles have high influence on pavement structure at the roads. Karami has and Gillespie in 1993 paid attention on pavement damage from trucks and how to predict dynamic loads along the roadways also the validity of the models is presented. The authors focused on characteristics of trucks and pavement, and also their interaction [6] [7]. In 1995, York and Maze briefly described applications of trucks size and weights standards in the US. This research contains evaluation of truck size and weight regulation in the United States and classification of performance criteria [8]. And in 2001 Nagatani has studied into the problem of modeling bunching transitions in general traffic flow and bus routes. Bunching models capture the tendency of moving objects to bunch together when moving in a line. This is usually due to some of the objects being operated or moving more efficiently than others. It can also be due to small unpredictable delays. Bunching is known to reduce a fleet‘s ability to meet its maximum capacity [9]. 22..33 CCOOMMPPUUTTEERRSS IINN EEAARRTTHHMMOOVVIINNGG Several attempts have been made to develop computer-aided tools to assist in equipment selection. For example, applications of simulation techniques to earthmoving operations were made in the 1960s [10]. In 1972, Willenbrock developed a model using a computer simulation language, GPSS (General Purpose Simulation System), to estimate cost for earthworks. The GPSS is a programming system designed for the simulation of discrete systems. These are systems that can be modeled as a series of state changes that occur instantaneously, usually over a period of time. Complexities in their analysis arise because there are many elements in the system, and there is competition for limited system resources. The simulation technique uses numerical computation methods to follow the system elements through their changes of state, and predicts properties of the system from measurements on the model. GPSS came into existence rapidly, with virtually no planning, and surprisingly little effort. It came rapidly because it filled an urgent
  28. 28. 13 need that left little time for exploring alternatives. The lack of planning came from a happy coincidence of a solution meeting its problem at the right time. The economy of effort was based on a background of experience in the type of application for which the language was designed, both on the part of the designer and the early users [10]. Simulation has been used extensively in many areas of Construction Engineering starting with the introduction of CYCLONE by Halpin in 1977. This methodology has been the basis for a number of construction simulation systems. Most of these systems are general in nature forcing users to build models using abstract elements such as activities, queues and resources. This allows for the modeling of scenarios of unlimited complexity and in any field. Further, if the basic building elements are not sufficient to a model a given situation, most systems also allow for the integration of programming code in the form of user inserts or add-ons. Although these systems prove extremely flexible and powerful from an academic stand point, those who can benefit from its power the most, the industry practitioners, have not embraced it. The generality and complexity of general purpose simulation systems meant that industry members were forced to learn the equivalent of a new language or hire an expensive simulation consultant to perform the required analysis. In the construction industry, simulation can be most beneficial during the estimating stage where limited time is available and costs incurred are typically not easily recovered since only a small amount of estimates lead to a successful contract award. Construction practitioners require a simulation tool that is easy to use and tailored to their specific requirements with results that can be directly used as part of other decision support systems such as computer estimating programs [11]. A linear programming model was presented by Mayer and Stark in 1981. In this model the earthmoving costs were split into three components: costs for excavation, costs for hauling, and costs for fill. These costs were linearly proportional to the quantity of material to be handled. The cost of purchasing mil at the borrow pits was also considered [12].
  29. 29. 14 In 1982, Luch and Halpin presented a Simulation model called MicroCYCLONE. MicroCYCLONE is a microcomputer based simulation program designed especially for modeling and analyzing site level processes which are cyclic in nature. In broader terms, it can be used to model construction operations which involve the interaction of tasks with their related duration, and the resource unit flow routes through the work tasks are the basic rationale for the modeling of construction operations [13]. In the two models discussed above, cost rates were assumed constant. By considering the variation in the unit cost of earthworks, an extension to the models was proposed by Easa [14] in 1987. It was found that the major variation in the unit cost of earthworks was the variation in the unit cost for purchasing and/or excavating the soil at the borrow pits. Therefore, a stepwise unit cost function of purchase and excavation for the borrow pits was modeled. Other cost components were still assumed to be constant. A further modification was made to the stepwise unit cost function by Easa [15] in 1988. In 1988, Alkass and Harris designed a system to aid in equipment selection for road construction. This system, ESEMPS, is an expert system [16].Expert systems function by asking the user a series of yes/no questions. As these questions are answered, a set of programmed rules allow the system to guide the user to the ―correct answer‖. This system is linked to a set of external databases which contain information on machines, earth types, etc. The system also calculates projected costs. In 1989,Ioannou designed a Simulation UM-CYCLONE model. UM CYCLONE is a discrete-event simulation system for construction operations based on activity scanning and activity cycle diagrams and runs under DOS [17]. In 1992, Amirkhanian and Baker developed an expert system specifically geared toward equipment selection. Their system, based in VP Expert, asks a series of questions about project conditions and then recommends the type and number of
  30. 30. 15 pieces of equipment needed. Equipment choices include dozers, scrapers, excavators and trucks [18]. Hanna in 1994 created a similar system for crane selection. In this system, the most appropriate type and size of crane or derrick is selected based on project parameters such as heaviest lift, maneuverability, and job conditions. The program produces output which lists the best type of crane, as well as setup parameters such as number of lifts for a tower crane. The main focus of the system is to eliminate or reduce the need for expensive consultations with crane experts. Results of the program were positive, though limited by the available database [19]. In 1994, AbouRizk and Shi developed an optimization model that considers only the quantities of resources being used along with their respective user-specified boundaries. The system recommends a resource combination, within the specified boundaries, closer to the optimum resource allocation [20]. In 1994, Huang et al. developed a DISCO Simulation model. The DISCO system provides a graphical environment in which modeling and simulation of construction operations can be conducted in an interactive fashion. The model developed for the bridge construction and the results of the simulation are presented [21]. In the same year Tommelein et al. designed a CIPROS which is a knowledge-based construction planning simulation system that enables its users to formalize and test alternative construction plans by relating project-specific design drawings and specifications to a network of construction processes, elementary simulation process networks, and associated resources [22]. In 1996, Christian and Xie developed an expert system built upon a rating system for various types of equipment. A survey was sent out to experts in the field seeking input on what type of machine was best for a variety of projects and soil types. This information was compiled into a table that rated each type of equipment from 0 to 10 (10being best) for each set of project parameters. The expert system asks a set of questions, and then uses the rating system to select the appropriate type and number of equipment[23].
  31. 31. 16 A STROBOSCOPE was proposed by Martinez in 1996. STROBOSCOPE is a simulation system designed as the successor to UM-CYCLONE based on activity scanning and activity cycle diagrams. The name STROBOSCOPE, an acronym for state and resource-Based Simulation of construction processes, reflects the system's major design objective: the ability to make complex dynamic decisions (and thus control the simulation at run-time) based on the simulation system state and the characteristics, attributes, and state of resources. Unlike other simulation systems, STROBOSCOPE is based on three-phase activity scanning and not process interaction. The activity scanning simulation paradigm makes STROBOSCOPE better suited for modeling complex resource interactions such as those that characterize cyclic operations where no distinction is made between resources that serve (servers or scarce resources) and those served (customers or moving entities). STROBOSCOPE simulation models use an easy-to-learn graphical network-based representation similar to activity cycle diagrams [24]. In the same year Sawhney and AbouRisk presented a HSM simulation system. HSM enhances and combines the concepts of work breakdown structure and process modeling to arrive at an advanced framework for planning [25]. Special purpose simulation (SPS) was proposed by AbouRizk and Hajjar in 1997 to address the stated issues. The idea is to develop user friendly simulation tools native to the application domain itself. This typically involves the development of custom user interfaces, simulation engines, support libraries and integration modules. By specializing, the full-fledged flexibility of a general purpose simulation tool is lost. However, the resultant benefits far outweigh the limitations. SPS tools allow industry practitioners to use simulation systems without prior knowledge of simulation theory [26]. And after one year MaCabe introduced belief networks as a diagnostic tool in order to obtain a near optimum solution, accounting for both the quantity and capacity of each utilized resource [27]. In 1999, SIMPHONY simulation system was proposed by AbouRizk and Hajjar which provides various services that enable the developer to easily control different behaviors in the developed tool such as simulation behaviors, graphical
  32. 32. 17 representation, statistics, and animation. These services allow building flexible and user friendly tools in a relatively short time [28]. In 2000, Naoum and Haidar have developed a genetic algorithm model for the equipment selection problem. Although their model satisfies the requirements for an integer programming solution, the authors pursued a genetic algorithm solution. The solution incorporates the lifetime discounted cost of the equipment, which is formally attached to the assumption that the equipment is used from purchase until official retirement age, and not sold or replaced before that time. The authors argue that intelligent search techniques are necessary because integer programming is incapable of solving a problem with more than one type of independent variable [29]. In the same year Kannan et al. recognize that despite the complementary role of academic research and industry applied simulation models, a gap exists between the two: academia follow ―opportunity driven‖ models and industry aims for ―need- based‖ models. The authors provide some defined requirements and ―success factors‖ for simulation programming. A short but directed literature survey of simulation modeling in the construction industry is also included [30]. In 2007, Bruno et al. propose a model using Stochastic Colored Petri Nets to represent the operational dynamics of earth moving work. For this purpose, a graphic and analytic model that represents the earth moving activities was idealized. As a conclusion of this study, it can be stated that Petri nets models provide an important instrument for decision makers when managing earth moving planning and execution [31]. In 2008, Kapur et al. presented a new methodology for integration of ‗variable productivity‘ data with a visualization model of earthwork operations. The paper presents a prototype of a 4D visualization model which is designed by integrating the road design data, quantities of cut and fill, productivity model, algorithms for modeling terrain surfaces and a progress profile visualize. The model generates automatically terrain surfaces of progress profiles for earthwork operations and visualizes progress profiles throughout the construction operations under different site and soil conditions. It is demonstrated with a real life case study in a road project [32].
  33. 33. 18 Finally Table 2.1 illustrates summary of the previous published models in the same field of study. Table 2.1: PROEQUIP and previous published models for earthmoving n Reference Model concept and name Description and Function 1 Willenbrock [10] Simulation (GPSS) to estimate cost for earthworks 2 Halpin [11] Simulation (CYCLONE) Allows the graphical representation and simulation of discrete systems that deals with deterministic or stochastic variables by dividing the construction process into work tasks 3 Mayer and Stark [12] Linear programming model Estimate excavation, hauling and fill cost 4 Luch and Halpin [13] Simulation (MicroCYCLONE) MicroCYCLONE is a microcomputer based simulation program designed specially for modeling and analyzing site level processes which are cyclic in nature. In broader terms, it can be used to model construction operations which involves the interaction of tasks with their related duration, and the resource unit flow routes through the work tasks are the basic rationale for the modeling of construction operations. 5 Easa [14] Mathematical model Modification and improvement in unit cost calculations 6 Easa [15] Mathematical model New modifications and improvement in unit cost calculations 7 Alkass and Harris [16] Expert system (ESEMPS) Aid system using for selecting the road construction equipment based on production rate 8 Ioannou [17] Simulation (UM- CYCLONE) UM CYCLONE is a discrete-event simulation system for construction operations based on activity scanning and activity cycle diagrams. UM CYCLONE runs under DOS
  34. 34. 19 9 Amirkhanian and Baker [18] Expert system Aid system using for selecting the equipment based on productivity for dozers, scrapers, excavators and trucks 10 Hanna [19] Mathematical model Selection the appropriate type and size of crane base on project parameters 11 Rizk and Shi [20] Mathematical model Advice the optimum resource allocation in construction sites 12 Huang et al. [21] Simulation (DISCO) The DISCO system provides a graphical environment in which modeling and simulation of construction operations can be conducted in an interactive fashion. The model developed for the bridge construction and the results of the simulation are presented. 13 Tommelein et al. [22] Simulation (CIPROS) CIPROS is a knowledge-based construction planning simulation system that enables its users to formalize and test alternative construction plans by relating project-specific design drawings and specifications to a network of construction processes, elementary simulation process networks, and associated resources. 14 Christian and Xie [23] Expert system Advice the best type of machine for variety of projects using rating system 15 Martinez [24] Simulation (STROBOSCOPE) STROBOSCOPE is a simulation system designed as the successor to UM-CYCLONE. Based on activity scanning and activity cycle diagrams. 16 Sawhney and AbouRisk [25] Simulation (HSM) HSM enhances and combines the concepts of work breakdown structure and process modeling to arrive at an advanced framework for planning. 17 AbouRizk and Hajjar [26] Simulation (SPS) Selecting the equipment based on productivity 18 MaCabe [27] Network model (MaCabe) Diagnostic tool to obtain a near optimum solution according for both quantity and capacity of each
  35. 35. 20 resource 19 AbouRizk and Hajjar [28] Simulation (SIMPHONY) provides various services that enable the developer to easily control different behaviors in the developed tool such as simulation behaviors, graphical representation, statistics, and animation. These services allow building flexible and userfriendly tools in a relatively short time. 20 Naoum and Haidar [29] Genetic algorithm Selecting the equipment based on life time discounted cost 21 Kannan et al. [30] simulation Selecting the earthmoving equipment based on literature survey 22 Bruno et al. [31] Stochastic colored Petri nets Instrument for planning earthmoving using graphic and analytic model using productivity results 23 Kapur et al. [32] new methodology for integration of ‗variable productivity‘ data with a visualization model 4D visualization model which is designed by integrating the road design data, quantities of cut and fill, productivity model, algorithms for modeling terrain surfaces and a progress profile visualize. The model generates automatically terrain surfaces of progress profiles for earthwork operations and visualizes progress profiles throughout the construction operations under different site and soil conditions. 24 Hassan Eliwah Simulation (PROEQUIP) It is an aid system using for earthmoving equipment selection based on equipment production rate only or equipment unit cost only or equipment production rate and equipment unit cost together.
  36. 36. CCHHAAPPTTEERR TTHHRREEEE EEAARRTTHHMMOOVVIINNGG OOPPEERRAATTIIOONNSS
  37. 37. 22 CCHHAAPPTTEERR 33 EEAARRTTHHMMOOVVIINNGG OOPPEERRAATTIIOONNSS 33..11 IINNTTRROODDUUCCTTIIOONN The function of heavy earthmoving equipment is to move or assist in the moving of soil and rock from point A to point B. The purchase of this equipment constitutes a particularly large investment on the part of the buyer. One cannot get into the business of owning this type of equipment without substantial cash reserves and/or financial backing. Regarding to that it is important that the reader have an understanding of basics concerning the construction equipment. This section will provide an introduction to the principles and vernacular of the field. The discussion will cover in general the hydraulic excavator and hauler equipment. 33..22 MMAANNAAGGIINNGG EEAARRTTHHMMOOVVIINNGG OOPPEERRAATTIIOONNSS The management of construction equipment is a difficult task. Equipment managers are often called upon to make complex economic decisions involving the machines in their charge. These decisions include those concerning acquisitions, maintenance, repairs, rebuilds, replacements, and retirements. The equipment manager must also be able to forecast internal rental rates for their machinery. Repair and maintenance expenditures can have significant impacts on these economic decisions and forecasts [33]. Managers must follow basic management phases to ensure that projects successfully meet deadlines set forth in project directives. Additionally, managers must ensure conformance to safety and environmental-protection standards. The basic management phases are planning, organizing, staffing, directing, controlling and executing [33].
  38. 38. 23 Proper equipment selection is crucial to achieving efficient earthmoving and construction operations. Consider the machine‘s operational capabilities and equipment availability when selecting a machine for a particular task. The manager should visualize how best to employ the available equipment based on soil considerations, zone of operation, project-specific requirements, equipment total cost and equipment productivity. Productivity estimates, productivity control, and productivity records are the basis for management decisions. Therefore, it is helpful to have a common method of recording, directing, and reporting production [34]. 33..22..11 SSaaffeettyy Engineers and safety officers are responsible for ensuring that personnel follow safety standards. Time is usually the controlling factor in construction operations in the theater of operations. The necessity for economy of time, coupled with the temporary nature of much of the work, sometimes results in safety precautions that are substantially lower than those used in civilian practice, but this does not mean safety can be ignored. Do not construe the lack of documentation of hazards as an indication of their nonexistence or insignificance. Where safety precautions are necessary but are not documented, or where existing precautions are judged to be inadequate, the commanding officer must issue new or supplementary warnings. Each job has its own particular safety hazards. Identify dangers and prepare a safety program to reduce or eliminate all hazards. Supervisors must conduct all operations following the guidance in the safety program [35]. The appropriate sections of safety manual identify safety rules for specific equipment. Also, check applicable technical and operator manuals prior too perating all equipment. Some general safety rules are as follows [35]:  Inspect equipment before use, and periodically on a regular basis.  Ensure that mechanized equipment is operated by qualified and authorized personnel only.  Use seat belts when they are available.
  39. 39. 24  Provide barriers to prevent personnel from walking under loading equipment that has a hoist or lift capability.  Operate equipment in a manner that will not endanger persons or property.  Observe safe operating speeds.  Shut down and turn off the engine when equipment is unattended.  Stop the equipment completely (apply the parking brake if available) before mounting or dismounting.  Do not operate any machinery or equipment for more than 10consecutive hours without an 8-hour rest interval.  Post the safe load capacities at the operator's position on all equipment not rigged to prevent overloading.  Post the safe operating speeds at the operator‘s position on all equipment not having a speed governor.  Ensure that only the operator is on the equipment while it is running.  Supervisors can authorize exceptions in emergency situations, some training situations, and when required for maintenance.  Shut down and turn off the engine when refueling motor vehicles and mechanized equipment. Before using a machine, a qualified, licensed operator should inspect and test the equipment to determine its safe operating condition. Equipment operator maintenance checks, service charts, and common sense ensure safe operation and proper maintenance. Tag any unsafe machinery or equipment ―Out of Service, Do Not Use‖ at the operator's position, to prevent its use until repaired. Ensure that the equipment‘s safety features (backup alarms, lights, and so on) are operational [35]. For special repair and maintenance procedures follow those items: [35]  Shut down or lock out equipment controls while a machine is being repaired, adjusted, or serviced.  Position the equipment in a place, away from the project area, that is safe for the mechanic to work.
  40. 40. 25  Crib or block suspended machinery, equipment, or parts, and machines held apart by slings, hoists, or jacks. Do not work underneath or between items not properly blocked.  Lower blades, bowls, hooks, buckets, and forks to the ground or onto suitable blocking material when equipment is undergoing maintenance or repairs. When operating equipment at night  Equip all mobile equipment with adequate headlights and taillights.  Keep construction roads and working areas well illuminated until all workers have left the area.  Ensure that signalers, spotters, inspectors, maintenance personnel, and others who work in dark areas exposed to vehicular traffic wear reflector zed vests or other such apparel if the tactical situation permits. When excavating  Shore, brace, or slope excavations that are more than 4 feet deep, unless working in solid rock, hard shale, hardpan, cemented sand and gravel, or other similar materials.  Design shoring and bracing to be effective all the way to the bottom of the excavation.  Use sheet piling, bracing, shoring, trench boxes, or other methods of protection, including sloping, based upon calculation of the pressures exerted by and the condition and nature of the materials being retained.  Provide additional shoring and bracing to prevent slides or cave-ins when excavating or trenching in locations adjacent to back-filled excavations or when subjected to vibrations from traffic, vehicles, or machinery.
  41. 41. 26 33..33 HHYYDDRRAAUULLIICC EEXXCCAAVVAATTOORRSS Hydraulic excavators (back hoe) are designed to excavate below the ground surface on which the machine rests. These machines have good mobility and are excellent for general-purpose work, such as excavating trenches and pits. Because of the hydraulic action of their stick and bucket cylinders, they exert positive forces crowding the bucket into the material to be excavated. The major components of the hydraulic hoe are the boom, the stick (arm), and the bucket. Fast-acting, variable- flow hydraulic systems give hydraulic excavators high implement speed and breakout force to excavate a variety of materials. There are many variations in hydraulic excavators. They may be either crawler or rubber-tire-carrier-mounted, and there are many different operating attachments. With the options in types, attachments, and sizes of machines, there are differences in appropriate applications and therefore variations in economical advantages [33]. Hydraulic power is the key to the advantages offered by these machines. The hydraulic control of machine components provides: [33] faster cycle times, Outstanding control of attachments, High overall efficiency, Smoothness and ease of operation and Positive control that offers greater accuracy and precision. Hydraulic excavators are classified by the digging motion of the hydraulically controlled boom and stick to which the bucket is attached. A downward arc unit is classified as a "hoe" [33]. To calculate the productivity of the excavator as a separate unit (not as an earthmoving system) use equation (3.1) [33]: Productivity = (3600 sec x Q x F x AS:D/t) x (E/60 min hr) x (1/VC) (3.1) where Q = heaped bucket capacity (Lcm), F = bucket fill factor, AS:D = angle of swing and depth (height) of cut correction, t = cycle time in seconds (table 3.3), E = efficiency (min per hour), VC = volume correction for loose volume to bank volume
  42. 42. 27 The main factors affect on excavators selection are (1) the cost per cubic meter of material excavated and (2) the job conditions under which the excavator will operate [33]. Unless the application calls for a lot of travel to, from, and around the job sites, a track-type excavator could be the better choice. Track-type excavators provide good traction and flotation in almost all kinds of underfoot conditions. Consistently good drawbar power provides excellent maneuverability. The tracked undercarriage also provides good overall stability. If the job calls for frequent machine repositioning, a track-type excavator will provide better operating efficiency where raising and lowering outriggers would take extra time (see Figure 3.1) [1]. A Wheel Excavator (see Figure 3.2) combines traditional excavator features such as 360° swing, long reach, deep digging depth, high loading height, high digging forces and high lift capacities, with the mobility of a wheeled undercarriage. The rubber tires allow the excavator to travel paved roads, work in shopping malls, squares, parking lots and other paved areas without damaging the pavement. Its mobility allows fast independent travel between jobsites as well as on the jobsite giving you more job planning flexibility [1]. Excavator buckets are rated to conform to both PCSA standard No. 3 (Power Crane and Shovel Association - Mobile Hydraulic Excavator Standards) and SAE standard J-296 (Society of Automotive Engineers, Inc. - Excavator, Mini-Excavator, and Backhoe Hoe Bucket Volumetric Rating) where the buckets are rated on both their struck and heaped capacities as follows [1]: Struck Capacity: Volume actually enclosed inside the outline of the side plates and rear and front bucket enclosures without any consideration for any material supported or carried by the spill plate or bucket teeth [1]. Heaped Capacity: Volume in the bucket under the strike off plane plus the volume of the heaped material above the strike off plane, having an angle of repose of 1:1 without any consideration for any material supported or carried by the bucket teeth (see Figure 3.3 and Figure 3.4) [1].
  43. 43. 28 Figure 3.1 Hydraulic hoe loading a truck. Figure 3.2 Wheel-mounted hydraulic hoe. Figure 3.3 Basic parts of a hydraulic hoe Figure 3.4 Hydraulic hoe bucket capacity rating dimensions. To maximize production of the earthmoving system, do the following: Ideal Bench Height and Truck Distance: For stable or consolidated materials, bench height should be about equal to stick length. For unstable materials it should be less. The most useful truck position is when the inside truck body rail is below the boom stick hinge pin [1]. Optimum Work Zone and Swing Angle: For maximum production, the work zone should be limited to 15° either side of machine center or about equal to
  44. 44. 29 undercarriage width. Trucks should be positioned as close as possible to machine centerline [1].Best Distance from the Edge; the machine should be positioned so that the stick is vertical when the bucket reaches full load. If the unit is farther back, breakout force is reduced. If it is closer to the edge, undercutting may occur and time is wasted bringing the stick back out (see Figure 3.5) [1]. Figure 3.5 Maximize production of the earthmoving system
  45. 45. 30 33..44 TTRRUUCCKKSS AANNDD HHAAUULLIINNGG OOPPEERRAATTIIOONNSS Since the 1930s most of the material moved out of open cut mines/quarries has been hauled by motorized trucks [33]. Whereas in underground mines material moved along the haulage drives has been in rail mounted trucks pushed or pulled by locomotives, and in recent times motorized truck haulage has been introduced underground. Trucks are hauling units that provide relatively low hauling costs because of their high travel speeds. The weight capacity of a truck may limit the volume of the load that a unit may haul. The productive capacity of a truck depends on the size of its load and the number of trips it can make in an hour. In transporting excavated material, processed aggregates, and construction materials, and for moving other pieces of construction equipment (see Figure3.6), trucks serve one purpose: they are hauling units that, because of their high travel speeds, provide relatively low hauling costs. The use of trucks as the primary hauling unit provides a high degree of flexibility, as the number in service can usually be increased or decreased easily to permit modifications in the total hauling capacity of a fleet. Most trucks may be operated over any haul road for which the surface is sufficiently firm and smooth, and on which the grades are not excessively steep. Some units are designated as off-highway trucks because their size and weight are greater than that permitted on public highways (see Figure3.7). Off- highway trucks are used for hauling materials in quarries and on large projects involving the movement of substantial amounts of earth and rock. On such projects, the size and costs of these large trucks is easily justified because of the increased production capability they provide [33]. Trucks can be classified by many factors, including [33] 1. The method of dumping the load rear-dump, bottom-dump, or side-dump. 2. The type of frame rigid-frame or articulated. 3. The size and type of engine gasoline, diesel, butane, or propane. 4. The kind of drive, for example two wheel 5. The number of wheels and axles
  46. 46. 31 6. The class of material hauled, for example rock material 7. The capacity 8. The type of work Trucks are classified under the type of work [1]:  Rigid Frame Trucks: for use in hauling many types of materials (see Figure3.8). The shape as the extent of sharp angles and corners.  Articulated Trucks: specifically designed to operate over rough soft ground, and in confined working locations where a rigid- frame truck would have problems (see Figure3.9, Figure 3.10)  Off-highway dump truck: the body floor slopes forward at a slight angle, typically less than 15° (see Figure3.11, Figure 3.12). Some of the current day manufacturers include: Komatsu, Terex, Unit Rig, Pay- hauler, Caterpillar, Euclid, Wabco, Bell, Liebherr, Tamrock [Toro], Atlas Copco- Wagner, Elphinstone and many others that have developed units for specific markets eg. The ―Kiruna‖ underground electric truck. Figure 3.6 Truck tractor unit towing Figure 3.7 Off-highway truck
  47. 47. 32 Figure 3.8 Highway rigid-frame rear- dump truck Figure 3.9 An articulated dump truck Figure 3.10 An articulated dump truck moving through soft ground Figure 3.11 Off-highway tractor towing a loaded bottom-dump trailer Figure 3.12 Highway bottom-dump
  48. 48. 33 There are at least three methods of rating the capacities of trucks and wagons: [33] 1. Gravimetric: the load that it will carry, expressed as a weight. 2. Struck volume: the volumetric amount it will carry, if the load was water level in the body (see Figure3.13). 3. Heaped volume: the volumetric amount it will carry, if the load was heaped on a 2:1 slope above the body (see Figure3.13). Figure 3.13 Measurement of volumetric capacity The productive capacity of a truck depends on the size of its load and the number of trips it can make in an hour. The number of trips completed per hour is a function of cycle time. Truck cycle time has four components: (1) load time, (2) haul time, (3) dump time, and (4) return time. Examining a match between truck body size and excavator bucket size yields the size of the load and the load time. The haul and return cycle times will depend on the weight of the vehicle, the horsepower of the engine, the haul and return distance, and the condition of the roads traversed. Dump time is a function of the type of equipment and conditions in the dump area [33].
  49. 49. CCHHAAPPTTEERR FFOOUURR EESSTTIIMMAATTIINNGG TTEECCHHNNIIQQUUEESS
  50. 50. 35 CCHHAAPPTTEERR 44 EESSTTIIMMAATTIINNGG TTEECCHHNNIIQQUUEESS 44..11 IINNTTRROODDUUCCTTIIOONN Earthmoving is the removal of existing material, which includes excavating or loading, transporting, grading and unloading materials. The productivity, or output, of earthmoving equipment can be defined as the total amount of material handled by a machine in a certain time [7]. In estimating productivity, the basic element needed to be analyzed is the productivity rate which is the amount of material a machine can handle in a unit time such as a minute or an hour. In this chapter, significant productivity factors common to different types of machines are first discussed. Following this, the factors influencing the productivity rates of specific types of machines are discussed. Problems in estimating machine productivity are determined and a model for adjusting productivity estimates is also proposed. There are two aspects to be considered in judging the appropriateness of a machine for a particular job. One is its technical applicability, including productive capacity; and the other is its economic feasibility [34]. In order to select appropriate machines, machine performance is usually used as a criterion and judged by estimating the unit costs which are costs spent on handling materials per unit volume. Estimating costs is a difficult task in earthmoving planning, and in reality construction organizations use different approaches to classify and calculate costs. This chapter discusses the productivity and cost estimating of earthmoving equipment and factors influencing productivity. The main elements of the costs are analyzed and methods for calculating the costs are presented.
  51. 51. 36 44..22 PPRROODDUUCCTTIIVVIITTYY EESSTTIIMMAATTIINNGG The most convenient and useful unit of work done and unit of time to use in calculating productivity for a particular piece of equipment or a particular job is a function of the specific work-task being analyzed. To make accurate and meaningful comparisons and conclusions about production, it is best to use standardized terms [33]. Depending on where a material is considered in the construction process, during excavation versus after compaction, the same material weight will occupy different volumes (Figure 4.1). Material volume can be measured in one of three states:  Bank cubic meter (BCM): A BCM is 1 cubic meter of material as it lies in its natural/undisturbed state.  Loose cubic meter (LCM): A LCM is 1 cubic meter of material after it has been disturbed by an excavation process.  Compacted cubic meter (CCM): A CCM is 1 cubic meter of material after compaction. Figure 4.1 Material-Volume Changes Caused by Construction Processes When manipulating the material in the construction process, its volume changes. (Tables 4.1, gives material-volume conversion and load factors [7]) The prime question for an earthmover is about the nature of the material‘s physical properties; for example, how easy is it to move? For earthmoving operations, material is placed in three categories—rock, soil (common earth), and unclassified.
  52. 52. 37 Table 4.1 Material Volume Conversion Factors Most earth and rock materials swell when removed from their natural resting place. The volume expands because of voids created during the excavation process. After establishing the general classification of a soil, estimate the percentage of swell. The quantity of material to be handled in an operation generally does not have a direct influence on the productivity rates of individual machines. When the duration of an operation has been set, however, it is a factor that should obviously be considered in determining the size and number of machines for the overall productivity of a fleet. In relation to the quantity, the physical state of the material is important for estimates. When material is in its undisturbed normal state, it is referred to as in situ, or bank, material, and usually occupies a fixed volume known as the in situ volume or bank volume. After king excavated from its original location, the volume of material expands due to the breakup of its naturally compressed part. The material is then in a loose state and its volume is known as the loose volume. The volume of a material varies from one state to the other, and has great impact on the productivity rates. Therefore, the system requires users to input what type of measure they take in estimating quantities. When users estimate the volume of a soil to be handled in the bank state, the system converts it into the loose
  53. 53. 38 volume since earthmoving machines actually handle mils in the loose state. When calculating productivity, it should always be tried to get an accurate measure of actual material weights and swell factor. Any companies or contractors which move material will usually calculate productivity in ton per cubic meter. Earthmoving contractors will usually get paid by the moved number of cuyd bank or m3 bank. During the productivity estimating, some factors should considered such Fill Factor Ratio between nominal volume and actual volume of a bucket or the body of a dump truck, given as percentage of nominal volumeand Load Factor: Converts the nominal payload volume of a dump truck (in loose cuyd or m3) into the effective loaded volume in bank cuyd or m3. Most material codes define the load factor LF as LF = Swell Factor SF x Fill Factor FF. Depending on the digging action of the equipment and the operational conditions, a excavator may under-fill or over-fill its bucket. This condition is measured by the bucket fill factor (ff) [34]. Bucket fill factor (ff) = loose vol. of material excavated in an average load nominal bucket capacity, Bc (4.1) Typical ff‘s for digging condition [34]: Easy: 1.0-1.2 or Medium:0.8-1.0 or Hard: 0.6-0.9. The bucket factor is a combination of swell factor and (ff). It enables the bucket capacity in terms of volume of material in BCM to be readily calculated. Bucket factor, Bf  bucket fill factor swell factor (4.2) So that: Bucket capacity (BCM) = nominal bucket capacity (Bc) x bucket factor (Bf) (4.3) The cycle time of excavator is the time taken to fill the bucket, swing the boom round to the dump position, dump the bucket-load into the truck or hopper and swing back to the digging position. For planning purposes, cycle times can be estimated from manufacturer‘s literature or time studies. Operator skill is an important factor. Table 4.2 lists a range of excavator cycle times [33].
  54. 54. 39 Table 4.2: Loading excavator cycle times for a 90o swing (seconds) Digging Conditions Capacity (Bm3 ) Easy Medium Medium- Hard Hard 3 3 5 5.5 6 8 9 11.5 15 19 35 18 20 21 21 22 23 24 26 27 29 30 23 25 26 26 27 28 28 30 32 34 36 28 29 30 30 31 32 32 33 35 37 40 32 33 34 34 35 36 37 38 40 42 45 Where easy digging - loose material e.g., sand, small gravel. Medium digging, partially consolidated materials e.g., clayey gravel, packed earth, anthracite. Medium-Hard - well blasted lime-stones, heavy & wet clays, weaker ores, gravel with large boulders. Hard - materials that require heavy blasting and tough plastic clays, eg, granite, strong limestone, taconite, strong ores [33]. Excavator cycle times are normally based on a 90o swing (S = 1). Obviously as the swing angle increases, the cycle time will increase. The cycle time can be modified accordingly by including a swing factor and typical values are listed in Table 4.3 [33]. Express swell as a percentage increase in volume (Table 4.4). For example, the swell of dry clay is 35 percent, which means that 1 cubic meter of clay in the bank
  55. 55. 40 state will fill a space of 1.35 cubic meters in a loosened state. Estimate the swell of a soil by referring to a table of material properties such as Table 4.4. In earthmoving work, it is common to compact soil to a higher density than it was in its natural state. This is because there is a correlation between higher density and increased strength, reduced settlement, improved bearing capacity, and lower permeability. The project specifications will state the density requirements. Soil weight affects the performance of the equipment. To estimate the equipment requirements of a job accurately, the unit weight of the material being moved must be known. Soil weight affects how dozers push, excavator load and truck load the material. Assume that the volumetric capacity of a truck is 14 cubic meters and that it has a rated load capacity of 20,000kgs. If the material being carried is relatively light (such as cinder), the load will exceed the volumetric capacity of the truck before reaching the gravimetric capacity. Conversely, if the load is gravel (which may weigh more than 3,000 kgs per cubic meter), it will exceed the gravimetric capacity before reaching the volumetric capacity [7]. NOTE: The same material weight will occupy different volumes in BCM, LCM, and CCM. In an earthmoving operation, the basic unit of comparison is usually BCM. Also, consider the material in its loose state (the volume of the load). Table 4.4 gives average material conversion factors for earth-volume changes. Use a load factor (see Table 4.4) to convert the volume of LCM measured to BCM measured (LCM x load factor = BCM). Use similar factors when converting material to a compacted state. The factors depend on the degree of compaction. Compute the load factor as follows: If 1 cubic meter of clay (bank state) = 1.35 cubic meters of clay (loose state), then 1 cubic meter of clay (loose state) = 0.74 cubic meter of clay (bank state). In this case, the load factor for dry clay is 0.74. This means that if a scraper is carrying 25 LCM of dry clay, it is carrying 18 BCM (25 x 0.74).
  56. 56. 41 Table 4.3: Excavator swing factors Angleof swing 45 60 75 90 120 150 180 Swing factor 1.20 1.10 1.05 1.00 0.91 0.84 0.77 Table 4.4: Weight of Materials according to German Norm DIN/VOB Weight of materials * bank lb/cuyd/kg/m3 swell in % swell factor loose lb/cuyd/kg/m3 Clay - natural bed 3400/2020 22 0.82 2800/1660 dry 3100/1840 24 0.80 2500/1480 wet 3500/2080 24 0.80 2800/1660 Clay with gravel - dry 2800/1660 17 0.86 2400/1420 wet 3100/1840 19 0.84 2600/1540 Decomposed rock 75% rock, 25% earth 4700/2790 42 0.70 3300/1960 50% rock, 50% earth 3850/2280 33 0.75 2900/1720 25% rock. 75% earth 3300/1960 24 0.80 2650/1570 Earth - dry packed 3200/1900 26 0.79 2550/1510 wet excavated 3400/2020 26 0.79 2700/1600 loam 2600/1540 23 0.81 2100/1250 Granite - broken 4600/2730 64 0.61 2800/1660 Gravel - pitrun 3650/2170 12 0.89 3260/1930 dry 2850/1690 12 0.89 2550/1510 Limestone - broken 4400/2610 69 0.59 2600/1540 crushed ----- ----- ----- 2600/1540 Sand - dry, loose 2700/1600 12 0.89 2400/1420 damp 3200/1900 12 0.89 2850/1690 wet 3500/2080 13 0.88 3100/1840 Sand with clay - loose 3400/2020 26 0.79 2700/1600 compacted ----- ----- ----- 4050/2400 Excavator productivity [7] Qs = Bc Bf C Sf A O (PTF) (4.4) Where: Qs=excavator productivity (Bm3 /hr), Bc =nominal bucket capacity (m3 ), Bf=bucket factor, C=theoretical cycles/hr for a 90o swing = 60/tc, tc=excavator cycle time for a 90o swing (mins), Sf=swing factor, A=mechanical availability during scheduled hours of work, O=job operational factor and PTF=propel time factor. Note: actual bucket capacity (B) = nominal bucket capacity (Bc) * bucket factor (Bf) (Bm3 )
  57. 57. 42 Truck Productivity [7] Let: Rated truck load, = Lt tons Average material density =  t/m3 Excavator bucket capacity = B m3 1. Number of passes required to load the truck = L x B t  (4.5) 2. Multiply by the excavator cycle time to obtain the time required to load the truck, tL 3. Estimate the haul distances within the pit and from the top of the pit to the ore/waste dumps. 4. Select suitable truck speeds for travelling up-grade loaded, on a level grade loaded and empty and down-grade, empty. These speeds may be obtained from charts and tables provided by the manufacturer; tup, tlevel1, tlevel2, tdown. 5. Estimate the time required to spot a truck at a shovel, ts. 6. Sum the above times to obtain the total truck cycle time, Tct Tct = tL + tup + tlevel1 + tlevel2 + tdown + ts mins (4.6) Number of truck cycles per hour = 60 Tct (4.7) Truck productivity, Qt = L x Tt ct 60 (4.8)
  58. 58. 43 The haul distance is a major determinant of productivity rates for the simple reason that with the increase of the length of haul distance, the time a machine spends on the haul and return route generally increases, and its productivity rate decreases. The total resistance is a major factor influencing productivity rates, since it could slow down the travel speed of a machine [7]. We can describe the total resistance as a summation of the grade and running resistance; Grade Resistance is a measure of the force that must be overcome to move a machine over unfavourable grades (uphill), grade assistance is a measure of the force that assists machine movement on favourable grades (downhill), grades are generally measured in percent slope, which is the ratio between vertical rise or fall and the horizontal distance in which the rise or fall occurs [7]. For example, a 1% grade is equivalent to a 1 m rise or fall for every 100 m of horizontal distance; a rise of 4.6 m in 50 m equals a 9.2% grade. Rolling Resistance (RR) is a measure of the force that must be overcome to roll or pull a wheel over the ground. It is affected by ground conditions and load, the deeper a wheel sinks into the ground, the higher the rolling resistance, Internal friction and tire flexing also contribute to rolling resistance, Experience has shown that minimum resistance is approximately 2% (1.5% for radial tyres or dual tyred trucks) of the gross machine weight (on tyres) or Resistance due to tire penetration is approximately 0.6% for each cm of tire penetration [7].Thus rolling resistance can be calculated using these relationships in the following manner: RR equal two percent of GMW plus 0.6 percent of GMW per cm tire penetration [7]. In terms of newtons it‘s a resistance per hundred kilograms of gross weight – from table of rolling resistance in newtons per thousand kilograms of gross weight of various road surfaces (Table 4.5) -. Other methods are derived from this basic expression. Total resistance can also be represented as consisting completely of grade resistance expressed in percent grade. In other words, the rolling resistance component is viewed as a corresponding quantity of additional adverse grade resistance. This can be done by converting the contribution of rolling resistance into a corresponding percentage of grade resistance. Since 1% of adverse grade offers a resistance of 10
  59. 59. 44 kg for each metric ton of machine weight, then each 10 kg resistance per ton of machine weight can be represented as an additional 1% of adverse grade. Table 4.5: ROLLING RESISTANCE FACTORS Under-footing Rolling Resistance Percent Tyres Bias Radial Track Track+ Tyres Very hard, smooth roadway, concrete, cold asphalt, no penetration or flexing 1.5% 1.2% 0% 1.0% Hard, smooth stabilised surfaced roadway no penetration under load, watered, maintained 2.0% 1.7% 0% 1.2% Dirtroadway, rutted under load, little maintenance, no watering,25mm tyre penetration 4.0% 4.0% 0% 2.4% Rutted dirt roadway, soft under travel, no maintenance, no stabilization, 100mm tyre penetration or flexing 8.0% 8.0% 0% 4.8% Very soft, muddy, rutted roadway 300mm tyre penetration, no flexing 20% 20% 8% 15% Various tyre sizes and inflation pressures will greatly reduce or increase the rolling resistance. The values in this table are approximate, particularly for the track and track + tyre machines. These value scan be used for estimating purposes when specific performance information on particular equipment and given soil conditions is not available [7]. By operating a machine skill-fully, a better operator usually spends less time on activities and this yields higher production. The production correction factor due to theski11 level of an operator can approximately be given as in Table 4.6 [1]. In routine operations, there is a certain amount of time spent on non-productive activities. To estimate the actual output produced in the productive time, job
  60. 60. 45 efficiency is often used to indicate the productive time as a fraction of the total time spent. The job efficiency is usually expressed as a percentage of productive time in minutes per hour (Table 4.7 and 4.8) [34]. In this research, it is assumed that the job efficiency covers al1 minor idle or delay times, and other miscellaneous times, etc. Table 4.6: Operator Skill Factor, FO Table 4.7: Job Efficiency Factor, Fe Table 4.8: Excavator operating efficiency Management Conditions Job conditions Excellent Good Fair Poor Excellent Good Fair Poor 0.83 0.76 0.72 0.63 0.80 0.73 0.69 0.61 0.77 0.70 0.66 0.59 0.70 0.64 0.60 0.54
  61. 61. 46 From all the previous data, we can calculate the truck productivity as the following: Step 1: Number of Bucket Loads: The first step in analyzing truck production is to determine the number of excavator bucket loads it takes to load the truck [33]. Balanced number of bucket loads = (Truck capacity (Lcm)) / (Bucket capacity (Lcm)) (4.9) Step 2: Load Time: The actual number of bucket loads placed on the truck should be an integer number. If one less bucket load is placed on the truck, the loading time will be reduced; but the truckload is also reduced. Sometimes job conditions will dictate that a fewer number of bucket loads be placed on the truck, i.e., the load size is adjusted if haul roads are in poor condition or if the trucks must traverse steep grades [33]: Load time = Number of bucket swings X bucket cycle time (4.10) Truckload (volumetric) = Number of bucket swings * volume of the bucket (4.11) If the division of truck body volume by the bucket volume is rounded to the next higher integer and that higher number of bucket swings is used to load the truck, excess material will spill off the truck. In such a case, the loading duration the bucket cycle time multiplied by the number of bucket swings. But the volume of the load on the truck equals the truck capacity, not the number of bucket swings multiplied by the bucket volume [33]: Truckload (gravimetric) = Volumetric (Lcm) * unit weight (loose vol. kg/Lcm) (4.12) Check: Truckload gravimetric < Rated gravimetric payload Step 3: Haul Time: Hauling should be at the highest safe speed and in the proper gear. To increase efficiency, use one-way traffic patterns. Based on the gross weight of the truck with the load, and considering the rolling and grade resistance from the
  62. 62. 47 loading area to the dump point, haul speeds can be determined using the truck manufacturer‘s performance chart (see Figure 4.2) [1] Haul time (min) = (Haul distance (m)) / (60 * 1000 * Haul speed (km/hr)) (4.13) Figure 4.2 Performance chart for Caterpillar 793C Truck The chart should be used to determine the maximum speed for each section of a haul road having a significant difference in grade or rolling resistance. While a performance chart indicates the maximum speed at which a vehicle can travel, the vehicle will not necessarily travel at this speed. Before using a performance chart speed in an analysis, always consider such factors as congestion, narrow roads, or traffic signals, when hauling on public roads, because these can limit the speed to less than the value given in the chart [33]. Step 4: Return Time: Based on the empty vehicle weight, rolling and grade resistance from the dump point to the loading area, return speeds can be determined using the truck manufacturer's performance chart:
  63. 63. 48 Return time (min) = (Return distance (m)) / (60 * 1000 * Return speed (km/hr)) (4.14) Step 5: Dump Time: Dump time will depend on the type of hauling unit and congestion in the dump area. Consider that the dumping area is usually crowded with support equipment. Total dumping time in such cases can exceed 2 min. After dumping, the truck normally turns and returns to the loading area. Under favorable conditions, a rear-dump can dump and turn in 0.7 min but an average unfavorable time is about 1.5 min. Bottom-dumps can dump in 0.3 min under favorable conditions, but they too may average 1.5 min when conditions are unfavorable [33]. Step 6: Truck Cycle Time: The cycle time of a truck is the sum of the load time, the haul time, the dump time, and the return time (Table 4.3): Truck cycle time = Load time + Haul time + Dump time + Return time (4.15) Figure 4.3 Basic truck load cycle.
  64. 64. 49 Step 7: Number of Trucks Required: The number of trucks required to keep the loading equipment working at capacity: Number of trucks = (Truck cycle time (min)) / (Load time (min)) (4.16) Step 8: Productivity: The number of trucks must be an integer number, so if an integer number of trucks lower than the result of Eq. (4.16) is chosen then the trucks will control production Productivity (Lcm/hr) = Truck load (Lcm) * Number trucks * (60 min / Truck cycle time (min)) (4.17) When an integer number of trucks greater than the result of Eq. (4.16) is selected, production is controlled by the loading equipment. Productivity (Lcm/hr) = Truck load (Lcm) * (60 / Load time) (4.18) Step 9: Efficiency: The productivity calculated with either Eq. (4.17) or (4.18) is based on a 60 min working hour. That productivity should be adjusted by an efficiency factor. Longer hauling distances usually result in better driver efficiency. Driver efficiency increases as haul distances increase out to about 3,000 m, after which efficiency remains constant [33]. Adjusted productivity (Lcm/hr) = Productivity (Lcm) * (Working time (min/hr)) / 60 min (4.19)
  65. 65. 50 44..33 CCOOSSTT EESSTTIIMMAATTIINNGG There are two aspects to be considered in judging the appropriateness of a machine for a particular job. One is its technical applicability, including productive capacity; and the other is its economic feasibility. In order to select appropriate machines, machine performance is usually used as a criterion and judged by estimating the unit costs which are costs spent on handling materials per unit volume. Estimating costs is a difficult task in earthmoving planning, and in reality construction organizations use different approaches to classify and calculate costs. This part discusses cost elements which are significant in methods for calculating earthmoving equipment costs. These methods are used to estimate costs in the computer modeling if the user has no readily established hourly costs available The unit cost of earthmoving works is essentially derived by dividing cost by production. In its simplest case, if you rented an excavator with operator for $60 per hour - including all fuel and other costs - and you excavated 100 cubic meters per hour, your unit cost for excavation would be $0.60 per cubic meter. The hourly cost of the excavator with operator is called the machine rate. In cases where the machine and the elements of production are not rented, a calculation of the owning and operating costs is necessary to derive the machine rate. The objective in developing a machine rate should be to arrive at a figure that, as nearly as possible, represents the cost of the work done under the operating conditions encountered and the accounting system in use. Most manufacturers of machinery supply data for the cost of owning and operating their equipment that will serve as the basis of machine rates. However, such data usually need modification to meet specific conditions of operation, and many owners of equipment will prefer to prepare their own rates [36]. The machine rate is usually, but not always, divided into fixed costs, operating costs, and labor costs. For certain cash flow analyses only items which represent a cash flow are included. Certain fixed costs, including depreciation and sometimes interest charges, are omitted if they do not represent a cash payment. In this
  66. 66. 51 research, all fixed costs discussed below are included. For some analyses, labor costs are not included in the machine rate. Instead, fixed and operating costs are calculated. Labor costs are then added separately. This is sometimes done in situations where the labor associated with the equipment works a different number of hours from the equipment. In this research, labor is included in the calculation of the machine rate. Fixed costs are those which can be predetermined as accumulating with the passage of time, rather than with the rate of work (Figure 4.4). They do not stop when the work stops and must be spread over the hours of work during the year. Commonly included in fixed costs are equipment depreciation, interest on investment, taxes, and storage, and insurance [36]. Figure 4.4 Equipment Cost Model. Operating costs vary directly with the rate of work (Figure 4.4). These costs include the costs of fuel, lubricants, tires, equipment maintenance and repairs. Labor costs are those costs associated with employing labor including direct wages, food contributions, transport, and social costs, including payments for health and
  67. 67. 52 retirement. The cost of supervision may also be spread over the labor costs. The machine rate is the sum of the fixed plus operating plus labor costs. The division of costs in these classifications is arbitrary although accounting rules suggest a rigid classification. The key point is to separate the costs in such a way as to make the most sense in explaining the cost of operating the men and equipment [36]. 44..33..11 FFiixxeedd CCoossttss Depreciation The objective of the depreciation charge is to recognize the decline of value of the machine as it is working at a specific task. This may differ from the accountant's depreciation schedule-which is chosen to maximize profit through the advantages of various types of tax laws and follows accounting convention. Depreciation schedules vary from the simplest approach, which is a straight line decline in value, to more sophisticated techniques which recognize the changing rate of value loss over time. The formula for the annual depreciation charge using the assumption of straight line decline in value is: [36] D = (P' - S)/N (4.20) where P' is the initial purchase price less the cost of tires, wire rope, or other parts which are subjected to the greatest rate of wear and can be easily replaced without effect upon the general mechanical condition of the machine. S is Salvage value which defined as the price that equipment can be sold for at the time of its disposal. N is Economic life which defined as the period over which the equipment can operate at an acceptable operating cost and productivity. Examples of ownership periods for some types of road construction equipment, based upon application and operating conditions, are shown in Table 4.9 [1].

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