SlideShare a Scribd company logo
1 of 28
Download to read offline
GROUND IMPROVEMENT BY
PRELOADING AND DRAINAGE
Prepared By:-
Sagar Halwawala (11BCL014)
Himanshu Manolkar (11BCL015)Himanshu Manolkar (11BCL015)
Satish Kambaliya (11BCL016)
Abhinav Karmilla (11BCL017)
Civil Engineering Department
Institute Of Technology Nirma University,
Ahmedabad
Introduction
• In times of urbanization, growth of population
and associated developments, construction
activities are more and more focused on soils
which were considered unsuitable in the past
decades. These soft soil deposits have a lowdecades. These soft soil deposits have a low
bearing capacity and exhibit large settlements
when subjected to loading. It is therefore
inevitable to treat soft soil deposits prior to
construction activities in order to prevent
differential settlements and subsequently
potential damages to structures.
Introduction cont.
• According to Bergado et al. (1996) ground
improvement techniques can be divided broadly
into two categories.
1. Technique which require foreign materials and
utilisation of reinforcements. They are based on
stiffening columns either by the use of astiffening columns either by the use of a
granular fill (stone columns), by piling elements
which are not reaching a still soil stratum (creep
piles) or by in situ mixing of the soil with
chemical agents (deep stabilisation).
2. Technique which includes strengthening of the
soil by dewatering, i.e. preloading techniques
often combined with vertical drains.
Preloading OR Precompression
• Preloading is surcharging the ground with a
uniformly distributed surface load prior to the
construction of the structure such as Buildings,
Embankments, Motorways, and Runways Tanks
etc.)etc.)
• The purpose is to take up the settlements under
the Civil Engineering structures before they are
built.
• Soils suitable for preloading: Compressible soft to
medium soft saturated clays and silts, organic
clays, peats.
Preloading cont.
Primary consolidation using Surcharge loading
Primary consolidation by using surcharge loading
• Types of preloads:
Earth fills (Most common), Water in tanks or
ponds, vaccum application under a membrane,
special anchor and jack systems, groundwater
lowering, electro osmosis.
• The surcharge results in;
Preloading cont.
• The surcharge results in;
1. Primary Consolidation Settlement
2. Secondary Consolidation Settlement
3. Increase in the undrained shear strength of the
soil.
Preloading Techniques
A. Conventional Preloading
• The simplest solution of preloading is a preload,
e. g. by means of an embankment.
• When the load is placed on the soft soil, it is
initially carried by the pore water. When the soil
is not very permeable, which is normally theis not very permeable, which is normally the
case; the water pressure will decrease gradually
because the pore water is only able to flow away
very slowly in vertical direction.
• In order not to create any stability problems, the
load must mostly be placed in two or more
stages.
Conventional Preloading cont.
The principle of
Conventional
Preloading
If the temporary
load exceeds theload exceeds the
final construction
load, the excess
refers to as
surcharge load.
Conventional Preloading cont.
• The temporary surcharge can be removed when the
settlements exceeds the predicted final settlement.
• This should preferably not happen before the
remaining excess pore pressure is below the stress
increase caused by the temporary surcharge.
• By increasing the time of temporary overloading, or
the size of the overload, secondary settlement can
be reduced or even eliminated.be reduced or even eliminated.
• This is because by using a surcharge higher than the
work load, the soil will always be in an over
consolidated state and the secondary compression
for over consolidated soil are much smaller than that
of normally consolidated soil. This will benefit greatly
the subsequent geotechnical design.
B. Vacuum Preloading
• Sometimes soft soil may be so weak that even a
common 1.5 m embankment might cause
stability problems. Then it can be suitable to use
the method of vacuum preloading.
• In 1952 Kjellman was the first who introduced
vacuum preloading to accelerate consolidation. Invacuum preloading to accelerate consolidation. In
vacuum consolidation the surcharge load is
replace by atmospheric pressure.
• In its simplest form the method of vacuum
consolidation consists of a system of vertical
drains and a drainage layer (sand) on top.
Vacuum Preloading Conti….
• The common advantages of vacuum preloading
are that there is no extra fill material needed, the
construction times are generally shorter and it
requires no heavy machinery. Moreover, norequires no heavy machinery. Moreover, no
chemical admixtures will penetrate into the
ground and thus it is an environmental friendly
ground improvement method.
Vacuum Preloading cont.
Vacuum Preloading cont.
Possible problems associated with vacuum
preloading are:
• To maintain an effective drainage system under
the membrane that expels water and air
throughout the whole pumping duration.
• Keeping non-water saturated medium below the• Keeping non-water saturated medium below the
membrane.
• To maintain an effective level of vacuum.
• To maintain a leak proof system in particular at
the pumps / membrane connections and over the
entire membrane area.
Vacuum Preloading cont.
• Anchoring and sealing of the system at the
periphery.
• Reducing lateral seepage towards the vacuum
area.area.
Principles of Preloading
Figure illustrates schematically a vertical stress profile
when a vacuum load (assuming 100 % efficiency) is
applied to the ground surface in comparison with initial
conditions and conventional surcharge.
a) initial in situ conditions
Principles of Preloading cont.
b) conventional surcharge c) vacuum induced surcharge
Vertical Drains
• Preloading technique may not work sometimes
alone due to a thick uniform soft clay layer or
permeability of the clay is very low.
• so time for precompression is very long and not
practical or surcharge will be very high for
reasonable waiting periods.reasonable waiting periods.
• Because of its low permeability, the consolidation
settlement of soft clays takes a long time to
complete. To shorten the consolidation time,
vertical drains are installed together with
preloading either by an embankment or by
means of vacuum pressure.
Vertical Drains cont.
• Therefore, the vertical drain installation reduces
the length of the drainage path and,
consequently, accelerates the consolidation
process and allows the clay to gain rapid strengthprocess and allows the clay to gain rapid strength
increase to carry the new load by its own.
Vertical Drains cont.
Preloading with vertical drains
Maximum Length [m]
Types of Vertical Drains
• Sand drains are basically boreholes filled with
sand. As for the displacement type of sand drains,
a closed mandrel is driven or pushed into the
ground with resulting displacement in both
vertical and horizontal directions.
• The installation causes therefore disturbances,
especially in soft and sensitive clays, whichespecially in soft and sensitive clays, which
reduces the shear strength and horizontal
permeability.
• The low- or non-displacement installations are
considered to have less disturbing effects on the
soil. Drilling of the hole is done by means of an
auger or water jets. In terms of jetting, however,
installation is very complex.
Types of Vertical Drains conti.
• The installation of prefabricated vertical drains is also
done by a mandrel and it is a displacement
installation. The dimensions of the prefabricated
drains are much smaller compared to sand drains
and subsequently are the dimensions of the
mandrel. Thus, the degree of soil disturbance caused
by the size of the mandrel during installations is
lower.
by the size of the mandrel during installations is
lower.
• At the tip of the mandrel is detachable shoe or
anchor made of a small piece of metal (given in
following figure). Sometimes it might also be a piece
of drain itself. The purpose of the anchor is to
prevent soil from entering the mandrel and plugging
it during penetration. It also keeps the drain at the
desired depth as the mandrel is withdrawn.
Some disadvantages of sand drains
• To receive adequate drainage properties, sand has to be
carefully chosen which might seldom be found close to
the construction site.
• Drains might become discontinuous because of careless
installation or horizontal soil displacement during the
consolidation process.
• During filling bulking of the sand might appear which
could lead to cavities and subsequently to collapse due tocould lead to cavities and subsequently to collapse due to
flooding.
• Construction problems and/or budgetary burdens might
arise due to the large diameter of sand drains.
• The disturbance of the soil surrounding each drain
caused by installation may reduce the permeability, the
flow of water of water to the drain and thus the
efficiency of the system.
• The reinforcing effect of sand drains may reduce the
effectiveness of preloading the subsoil.
Drain Properties
• Equivalent diameter for band-shaped drains
The theory of consolidation with vertical drains assumes that the
vertical drains are circular in their cross-section. Since most of the
prefabricated drains are rectangular in cross-section, the
rectangular drain has to be converted into an equivalent cylindrical
shape. That implies that the equivalent diameter has the same
theoretical radial drainage capacity as the band-shaped drain. The
equivalent diameter (dw) of a band-shaped drain with width (a) and
thickness (b) as given below.
Discharge Capacity
The discharge capacity depends on the following factors:
• Lateral earth pressure: By increasing lateral pressure, the filter
passes into the core and subsequently decreases the discharge
capacity due to a reduction of the cross-sectional area available for
flow.
• Large settlements: During consolidation, the ground will be
subjected to large settlements. Thus, the drains tend to settle
together with the ground which will result in bending of folding of
the drain.
• Clogging of drain: In the initial filtering process of flow from the soil• Clogging of drain: In the initial filtering process of flow from the soil
through the drain filter, the displaced water will contain a small
portion of fine particles. These may be deposited with the core
channels and may lead to clogging of the drain.
• Time: The discharge capacity may be reduced due to aging in the
soil after installation, possibly due to biological and chemical
activities.
• Hydraulic gradient: The measured discharge capacity varies with
different hydraulic gradients and is smaller when a higher hydraulic
gradient is used. This might be due to the loss of flow energy as a
result of turbulent flow at a high hydraulic gradient.
Properties of the filter
The filter has to meet the following requirements:
• The permeability of the filter should be high enough
not to influence the discharge capacity of the drain
system.
• On the contrary, the permeability of the filter should
be low enough to retain fine soil particles. The soil
particles might penetrate through the filter into the
core, which eventually might be filled with soil and getcore, which eventually might be filled with soil and get
clogged.
• The filter needs to be strong enough to withstand high
lateral pressure in order not to be squeezed into
channel system of the core.
• The filter should be strong enough not to break during
installation, and
• The filter should not deteriorate with time because this
would reduce the discharge capacity of the drain.
CONCLUSION
• A system of prefabricated vertical drains(PVDs) combined with
vacuum preloading is an effective method for accelerating soil
consolidation.
• It is clear that the application of PVDs combined with vacuum and
surcharge preloading has become common practice, and is now
considered to be one of the most effective ground improvement
techniques.
• Analytical and numerical modelling of vacuum preloading is still a• Analytical and numerical modelling of vacuum preloading is still a
developing research area. There has always been a discrepancy
between the predictions and observed performance of
embankments stabilised with vertical drains and vacuum pressure.
• Vacuum assisted consolidation is an innovative method which has
recently, and successfully, been used for large scale projects on very
soft soils in reclamation areas. The extent of surcharge fill can be
decreased to achieve the same amount of settlement and the
lateral yield of the soft soil can be controlled by PVDs used in
conjunction with vacuum pressure.
ThankThankThankThankThankThankThankThank
YouYouYouYouYouYouYouYou

More Related Content

What's hot

Design and construction of well foundations
Design and construction of well foundationsDesign and construction of well foundations
Design and construction of well foundationsDar Hilal
 
Ground improvement techniques compaction vibration
Ground improvement techniques  compaction vibrationGround improvement techniques  compaction vibration
Ground improvement techniques compaction vibrationAnjana R Menon
 
Ground Improvement Techniques
Ground Improvement TechniquesGround Improvement Techniques
Ground Improvement TechniquesNilesh Bhosale
 
Types of joints in rigid pavement
Types of joints in rigid pavementTypes of joints in rigid pavement
Types of joints in rigid pavementBhavya Jaiswal
 
Soil stabilisation (1)
Soil stabilisation (1)Soil stabilisation (1)
Soil stabilisation (1)Safiullah Khan
 
Dewatering techniques
Dewatering techniquesDewatering techniques
Dewatering techniquesjamali husain
 
Chapter 3 shallow foundations
Chapter 3 shallow foundationsChapter 3 shallow foundations
Chapter 3 shallow foundationsKHUSHBU SHAH
 
Vibration method for ground improvement technique
Vibration method for ground improvement techniqueVibration method for ground improvement technique
Vibration method for ground improvement techniqueABHISHEK THAKKAE
 
Flexible and-rigid-pavements
Flexible and-rigid-pavementsFlexible and-rigid-pavements
Flexible and-rigid-pavementsHARITSEHRAWAT
 
Ground improvement techniques
Ground improvement techniquesGround improvement techniques
Ground improvement techniquesEsri India
 
Bearing capacity_of_soil
 Bearing capacity_of_soil Bearing capacity_of_soil
Bearing capacity_of_soilShivarajteggi
 

What's hot (20)

Design and construction of well foundations
Design and construction of well foundationsDesign and construction of well foundations
Design and construction of well foundations
 
Ground improvement techniques compaction vibration
Ground improvement techniques  compaction vibrationGround improvement techniques  compaction vibration
Ground improvement techniques compaction vibration
 
Pile foundation ppt
Pile foundation pptPile foundation ppt
Pile foundation ppt
 
Dewatering by well point system
Dewatering by well point systemDewatering by well point system
Dewatering by well point system
 
Ground Improvement Techniques
Ground Improvement TechniquesGround Improvement Techniques
Ground Improvement Techniques
 
Types of joints in rigid pavement
Types of joints in rigid pavementTypes of joints in rigid pavement
Types of joints in rigid pavement
 
Soil stabilisation (1)
Soil stabilisation (1)Soil stabilisation (1)
Soil stabilisation (1)
 
Dewatering techniques
Dewatering techniquesDewatering techniques
Dewatering techniques
 
Chapter 3 shallow foundations
Chapter 3 shallow foundationsChapter 3 shallow foundations
Chapter 3 shallow foundations
 
Grouting
Grouting Grouting
Grouting
 
Vibration method for ground improvement technique
Vibration method for ground improvement techniqueVibration method for ground improvement technique
Vibration method for ground improvement technique
 
Flexible and-rigid-pavements
Flexible and-rigid-pavementsFlexible and-rigid-pavements
Flexible and-rigid-pavements
 
Ground improvement techniques
Ground improvement techniquesGround improvement techniques
Ground improvement techniques
 
Settlement of soil/foundation
Settlement of soil/foundationSettlement of soil/foundation
Settlement of soil/foundation
 
Bearing capacity_of_soil
 Bearing capacity_of_soil Bearing capacity_of_soil
Bearing capacity_of_soil
 
Wash boring
Wash boringWash boring
Wash boring
 
Soil Compaction
Soil CompactionSoil Compaction
Soil Compaction
 
Vacuum dewatering
Vacuum dewateringVacuum dewatering
Vacuum dewatering
 
Curing of concrete
Curing of concreteCuring of concrete
Curing of concrete
 
Vertical Drain
Vertical Drain Vertical Drain
Vertical Drain
 

Similar to Ground improvement technique

Chapter 6.0 modern foundation tech. & ground improvement
Chapter 6.0   modern foundation tech. & ground improvement Chapter 6.0   modern foundation tech. & ground improvement
Chapter 6.0 modern foundation tech. & ground improvement DYPCET
 
sand drain for consolidation settlement
sand drain for consolidation settlementsand drain for consolidation settlement
sand drain for consolidation settlementsubhamkabu123
 
Lecture-6 Earthdams.pptx
Lecture-6 Earthdams.pptxLecture-6 Earthdams.pptx
Lecture-6 Earthdams.pptxAleemNawaz6
 
dewateringtechniques 2.pptx
dewateringtechniques 2.pptxdewateringtechniques 2.pptx
dewateringtechniques 2.pptxCarolTumaneng
 
Presentation application-of-geosynthetics-in-canal
Presentation application-of-geosynthetics-in-canalPresentation application-of-geosynthetics-in-canal
Presentation application-of-geosynthetics-in-canalIEI GSC
 
International Journal of Engineering Research and Development
International Journal of Engineering Research and DevelopmentInternational Journal of Engineering Research and Development
International Journal of Engineering Research and DevelopmentIJERD Editor
 
Types of Flexible Pavements
Types of Flexible PavementsTypes of Flexible Pavements
Types of Flexible PavementsArnabKarmakar18
 
Cofferdam_ppt.pptx
Cofferdam_ppt.pptxCofferdam_ppt.pptx
Cofferdam_ppt.pptxJackRider12
 
Pre fabricated vertical drain and stone columns
Pre fabricated vertical drain and stone columnsPre fabricated vertical drain and stone columns
Pre fabricated vertical drain and stone columnsRavi Bhadani
 
Dynamic_compaction.pptx
Dynamic_compaction.pptxDynamic_compaction.pptx
Dynamic_compaction.pptxRam Deshpande
 
Civil Engineering-Dewatering
Civil Engineering-DewateringCivil Engineering-Dewatering
Civil Engineering-DewateringMoe Abadla
 
EXCAVATION FOR FOUNDATION - Methods & Temporary Earth Retaining Structures
EXCAVATION FOR FOUNDATION - Methods & Temporary Earth Retaining StructuresEXCAVATION FOR FOUNDATION - Methods & Temporary Earth Retaining Structures
EXCAVATION FOR FOUNDATION - Methods & Temporary Earth Retaining StructuresShivananda Roy
 

Similar to Ground improvement technique (20)

Chapter 6.0 modern foundation tech. & ground improvement
Chapter 6.0   modern foundation tech. & ground improvement Chapter 6.0   modern foundation tech. & ground improvement
Chapter 6.0 modern foundation tech. & ground improvement
 
sand drain for consolidation settlement
sand drain for consolidation settlementsand drain for consolidation settlement
sand drain for consolidation settlement
 
5. Dewatering.pdf
5. Dewatering.pdf5. Dewatering.pdf
5. Dewatering.pdf
 
Lecture-6 Earthdams.pptx
Lecture-6 Earthdams.pptxLecture-6 Earthdams.pptx
Lecture-6 Earthdams.pptx
 
ground improvement
ground improvementground improvement
ground improvement
 
5. Dewatering F1.pdf
5. Dewatering F1.pdf5. Dewatering F1.pdf
5. Dewatering F1.pdf
 
Akash verma.pptx
Akash verma.pptxAkash verma.pptx
Akash verma.pptx
 
dewateringtechniques 2.pptx
dewateringtechniques 2.pptxdewateringtechniques 2.pptx
dewateringtechniques 2.pptx
 
Presentation application-of-geosynthetics-in-canal
Presentation application-of-geosynthetics-in-canalPresentation application-of-geosynthetics-in-canal
Presentation application-of-geosynthetics-in-canal
 
International Journal of Engineering Research and Development
International Journal of Engineering Research and DevelopmentInternational Journal of Engineering Research and Development
International Journal of Engineering Research and Development
 
Types of Flexible Pavements
Types of Flexible PavementsTypes of Flexible Pavements
Types of Flexible Pavements
 
Cofferdam_ppt.pptx
Cofferdam_ppt.pptxCofferdam_ppt.pptx
Cofferdam_ppt.pptx
 
Pre fabricated vertical drain and stone columns
Pre fabricated vertical drain and stone columnsPre fabricated vertical drain and stone columns
Pre fabricated vertical drain and stone columns
 
Earthen Dams
Earthen DamsEarthen Dams
Earthen Dams
 
Dynamic_compaction.pptx
Dynamic_compaction.pptxDynamic_compaction.pptx
Dynamic_compaction.pptx
 
6. Pavement Engineering.pdf
6. Pavement Engineering.pdf6. Pavement Engineering.pdf
6. Pavement Engineering.pdf
 
Civil Engineering-Dewatering
Civil Engineering-DewateringCivil Engineering-Dewatering
Civil Engineering-Dewatering
 
Dam engineering i 5
Dam engineering i 5Dam engineering i 5
Dam engineering i 5
 
EXCAVATION FOR FOUNDATION - Methods & Temporary Earth Retaining Structures
EXCAVATION FOR FOUNDATION - Methods & Temporary Earth Retaining StructuresEXCAVATION FOR FOUNDATION - Methods & Temporary Earth Retaining Structures
EXCAVATION FOR FOUNDATION - Methods & Temporary Earth Retaining Structures
 
Well Foundation
Well FoundationWell Foundation
Well Foundation
 

More from Satish Kambaliya

Earthquake and earthquake resistant design
Earthquake and earthquake resistant designEarthquake and earthquake resistant design
Earthquake and earthquake resistant designSatish Kambaliya
 
Experimental study of precast portal frame
Experimental study of precast portal frameExperimental study of precast portal frame
Experimental study of precast portal frameSatish Kambaliya
 
Bot(build operate transfer)
Bot(build operate transfer)Bot(build operate transfer)
Bot(build operate transfer)Satish Kambaliya
 
Object markers and reflector unit marking
Object markers and reflector unit markingObject markers and reflector unit marking
Object markers and reflector unit markingSatish Kambaliya
 

More from Satish Kambaliya (6)

Earthquake and earthquake resistant design
Earthquake and earthquake resistant designEarthquake and earthquake resistant design
Earthquake and earthquake resistant design
 
Experimental study of precast portal frame
Experimental study of precast portal frameExperimental study of precast portal frame
Experimental study of precast portal frame
 
Bot(build operate transfer)
Bot(build operate transfer)Bot(build operate transfer)
Bot(build operate transfer)
 
Object markers and reflector unit marking
Object markers and reflector unit markingObject markers and reflector unit marking
Object markers and reflector unit marking
 
Foundation and its types
Foundation and its typesFoundation and its types
Foundation and its types
 
Visakhapatnam port
Visakhapatnam portVisakhapatnam port
Visakhapatnam port
 

Recently uploaded

Maximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdf
Maximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdfMaximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdf
Maximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdfTechSoup
 
5 charts on South Africa as a source country for international student recrui...
5 charts on South Africa as a source country for international student recrui...5 charts on South Africa as a source country for international student recrui...
5 charts on South Africa as a source country for international student recrui...CaraSkikne1
 
Patient Counselling. Definition of patient counseling; steps involved in pati...
Patient Counselling. Definition of patient counseling; steps involved in pati...Patient Counselling. Definition of patient counseling; steps involved in pati...
Patient Counselling. Definition of patient counseling; steps involved in pati...raviapr7
 
CapTechU Doctoral Presentation -March 2024 slides.pptx
CapTechU Doctoral Presentation -March 2024 slides.pptxCapTechU Doctoral Presentation -March 2024 slides.pptx
CapTechU Doctoral Presentation -March 2024 slides.pptxCapitolTechU
 
The basics of sentences session 10pptx.pptx
The basics of sentences session 10pptx.pptxThe basics of sentences session 10pptx.pptx
The basics of sentences session 10pptx.pptxheathfieldcps1
 
M-2- General Reactions of amino acids.pptx
M-2- General Reactions of amino acids.pptxM-2- General Reactions of amino acids.pptx
M-2- General Reactions of amino acids.pptxDr. Santhosh Kumar. N
 
How to Use api.constrains ( ) in Odoo 17
How to Use api.constrains ( ) in Odoo 17How to Use api.constrains ( ) in Odoo 17
How to Use api.constrains ( ) in Odoo 17Celine George
 
AUDIENCE THEORY -- FANDOM -- JENKINS.pptx
AUDIENCE THEORY -- FANDOM -- JENKINS.pptxAUDIENCE THEORY -- FANDOM -- JENKINS.pptx
AUDIENCE THEORY -- FANDOM -- JENKINS.pptxiammrhaywood
 
How to Add a many2many Relational Field in Odoo 17
How to Add a many2many Relational Field in Odoo 17How to Add a many2many Relational Field in Odoo 17
How to Add a many2many Relational Field in Odoo 17Celine George
 
P4C x ELT = P4ELT: Its Theoretical Background (Kanazawa, 2024 March).pdf
P4C x ELT = P4ELT: Its Theoretical Background (Kanazawa, 2024 March).pdfP4C x ELT = P4ELT: Its Theoretical Background (Kanazawa, 2024 March).pdf
P4C x ELT = P4ELT: Its Theoretical Background (Kanazawa, 2024 March).pdfYu Kanazawa / Osaka University
 
What is the Future of QuickBooks DeskTop?
What is the Future of QuickBooks DeskTop?What is the Future of QuickBooks DeskTop?
What is the Future of QuickBooks DeskTop?TechSoup
 
How to Show Error_Warning Messages in Odoo 17
How to Show Error_Warning Messages in Odoo 17How to Show Error_Warning Messages in Odoo 17
How to Show Error_Warning Messages in Odoo 17Celine George
 
Patterns of Written Texts Across Disciplines.pptx
Patterns of Written Texts Across Disciplines.pptxPatterns of Written Texts Across Disciplines.pptx
Patterns of Written Texts Across Disciplines.pptxMYDA ANGELICA SUAN
 
How to Manage Cross-Selling in Odoo 17 Sales
How to Manage Cross-Selling in Odoo 17 SalesHow to Manage Cross-Selling in Odoo 17 Sales
How to Manage Cross-Selling in Odoo 17 SalesCeline George
 
How to Add Existing Field in One2Many Tree View in Odoo 17
How to Add Existing Field in One2Many Tree View in Odoo 17How to Add Existing Field in One2Many Tree View in Odoo 17
How to Add Existing Field in One2Many Tree View in Odoo 17Celine George
 
DUST OF SNOW_BY ROBERT FROST_EDITED BY_ TANMOY MISHRA
DUST OF SNOW_BY ROBERT FROST_EDITED BY_ TANMOY MISHRADUST OF SNOW_BY ROBERT FROST_EDITED BY_ TANMOY MISHRA
DUST OF SNOW_BY ROBERT FROST_EDITED BY_ TANMOY MISHRATanmoy Mishra
 
Presentation on the Basics of Writing. Writing a Paragraph
Presentation on the Basics of Writing. Writing a ParagraphPresentation on the Basics of Writing. Writing a Paragraph
Presentation on the Basics of Writing. Writing a ParagraphNetziValdelomar1
 
Prescribed medication order and communication skills.pptx
Prescribed medication order and communication skills.pptxPrescribed medication order and communication skills.pptx
Prescribed medication order and communication skills.pptxraviapr7
 

Recently uploaded (20)

Maximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdf
Maximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdfMaximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdf
Maximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdf
 
5 charts on South Africa as a source country for international student recrui...
5 charts on South Africa as a source country for international student recrui...5 charts on South Africa as a source country for international student recrui...
5 charts on South Africa as a source country for international student recrui...
 
Patient Counselling. Definition of patient counseling; steps involved in pati...
Patient Counselling. Definition of patient counseling; steps involved in pati...Patient Counselling. Definition of patient counseling; steps involved in pati...
Patient Counselling. Definition of patient counseling; steps involved in pati...
 
CapTechU Doctoral Presentation -March 2024 slides.pptx
CapTechU Doctoral Presentation -March 2024 slides.pptxCapTechU Doctoral Presentation -March 2024 slides.pptx
CapTechU Doctoral Presentation -March 2024 slides.pptx
 
Prelims of Kant get Marx 2.0: a general politics quiz
Prelims of Kant get Marx 2.0: a general politics quizPrelims of Kant get Marx 2.0: a general politics quiz
Prelims of Kant get Marx 2.0: a general politics quiz
 
The basics of sentences session 10pptx.pptx
The basics of sentences session 10pptx.pptxThe basics of sentences session 10pptx.pptx
The basics of sentences session 10pptx.pptx
 
M-2- General Reactions of amino acids.pptx
M-2- General Reactions of amino acids.pptxM-2- General Reactions of amino acids.pptx
M-2- General Reactions of amino acids.pptx
 
How to Use api.constrains ( ) in Odoo 17
How to Use api.constrains ( ) in Odoo 17How to Use api.constrains ( ) in Odoo 17
How to Use api.constrains ( ) in Odoo 17
 
Finals of Kant get Marx 2.0 : a general politics quiz
Finals of Kant get Marx 2.0 : a general politics quizFinals of Kant get Marx 2.0 : a general politics quiz
Finals of Kant get Marx 2.0 : a general politics quiz
 
AUDIENCE THEORY -- FANDOM -- JENKINS.pptx
AUDIENCE THEORY -- FANDOM -- JENKINS.pptxAUDIENCE THEORY -- FANDOM -- JENKINS.pptx
AUDIENCE THEORY -- FANDOM -- JENKINS.pptx
 
How to Add a many2many Relational Field in Odoo 17
How to Add a many2many Relational Field in Odoo 17How to Add a many2many Relational Field in Odoo 17
How to Add a many2many Relational Field in Odoo 17
 
P4C x ELT = P4ELT: Its Theoretical Background (Kanazawa, 2024 March).pdf
P4C x ELT = P4ELT: Its Theoretical Background (Kanazawa, 2024 March).pdfP4C x ELT = P4ELT: Its Theoretical Background (Kanazawa, 2024 March).pdf
P4C x ELT = P4ELT: Its Theoretical Background (Kanazawa, 2024 March).pdf
 
What is the Future of QuickBooks DeskTop?
What is the Future of QuickBooks DeskTop?What is the Future of QuickBooks DeskTop?
What is the Future of QuickBooks DeskTop?
 
How to Show Error_Warning Messages in Odoo 17
How to Show Error_Warning Messages in Odoo 17How to Show Error_Warning Messages in Odoo 17
How to Show Error_Warning Messages in Odoo 17
 
Patterns of Written Texts Across Disciplines.pptx
Patterns of Written Texts Across Disciplines.pptxPatterns of Written Texts Across Disciplines.pptx
Patterns of Written Texts Across Disciplines.pptx
 
How to Manage Cross-Selling in Odoo 17 Sales
How to Manage Cross-Selling in Odoo 17 SalesHow to Manage Cross-Selling in Odoo 17 Sales
How to Manage Cross-Selling in Odoo 17 Sales
 
How to Add Existing Field in One2Many Tree View in Odoo 17
How to Add Existing Field in One2Many Tree View in Odoo 17How to Add Existing Field in One2Many Tree View in Odoo 17
How to Add Existing Field in One2Many Tree View in Odoo 17
 
DUST OF SNOW_BY ROBERT FROST_EDITED BY_ TANMOY MISHRA
DUST OF SNOW_BY ROBERT FROST_EDITED BY_ TANMOY MISHRADUST OF SNOW_BY ROBERT FROST_EDITED BY_ TANMOY MISHRA
DUST OF SNOW_BY ROBERT FROST_EDITED BY_ TANMOY MISHRA
 
Presentation on the Basics of Writing. Writing a Paragraph
Presentation on the Basics of Writing. Writing a ParagraphPresentation on the Basics of Writing. Writing a Paragraph
Presentation on the Basics of Writing. Writing a Paragraph
 
Prescribed medication order and communication skills.pptx
Prescribed medication order and communication skills.pptxPrescribed medication order and communication skills.pptx
Prescribed medication order and communication skills.pptx
 

Ground improvement technique

  • 1. GROUND IMPROVEMENT BY PRELOADING AND DRAINAGE Prepared By:- Sagar Halwawala (11BCL014) Himanshu Manolkar (11BCL015)Himanshu Manolkar (11BCL015) Satish Kambaliya (11BCL016) Abhinav Karmilla (11BCL017) Civil Engineering Department Institute Of Technology Nirma University, Ahmedabad
  • 2. Introduction • In times of urbanization, growth of population and associated developments, construction activities are more and more focused on soils which were considered unsuitable in the past decades. These soft soil deposits have a lowdecades. These soft soil deposits have a low bearing capacity and exhibit large settlements when subjected to loading. It is therefore inevitable to treat soft soil deposits prior to construction activities in order to prevent differential settlements and subsequently potential damages to structures.
  • 3. Introduction cont. • According to Bergado et al. (1996) ground improvement techniques can be divided broadly into two categories. 1. Technique which require foreign materials and utilisation of reinforcements. They are based on stiffening columns either by the use of astiffening columns either by the use of a granular fill (stone columns), by piling elements which are not reaching a still soil stratum (creep piles) or by in situ mixing of the soil with chemical agents (deep stabilisation). 2. Technique which includes strengthening of the soil by dewatering, i.e. preloading techniques often combined with vertical drains.
  • 4. Preloading OR Precompression • Preloading is surcharging the ground with a uniformly distributed surface load prior to the construction of the structure such as Buildings, Embankments, Motorways, and Runways Tanks etc.)etc.) • The purpose is to take up the settlements under the Civil Engineering structures before they are built. • Soils suitable for preloading: Compressible soft to medium soft saturated clays and silts, organic clays, peats.
  • 5. Preloading cont. Primary consolidation using Surcharge loading Primary consolidation by using surcharge loading
  • 6. • Types of preloads: Earth fills (Most common), Water in tanks or ponds, vaccum application under a membrane, special anchor and jack systems, groundwater lowering, electro osmosis. • The surcharge results in; Preloading cont. • The surcharge results in; 1. Primary Consolidation Settlement 2. Secondary Consolidation Settlement 3. Increase in the undrained shear strength of the soil.
  • 7. Preloading Techniques A. Conventional Preloading • The simplest solution of preloading is a preload, e. g. by means of an embankment. • When the load is placed on the soft soil, it is initially carried by the pore water. When the soil is not very permeable, which is normally theis not very permeable, which is normally the case; the water pressure will decrease gradually because the pore water is only able to flow away very slowly in vertical direction. • In order not to create any stability problems, the load must mostly be placed in two or more stages.
  • 8. Conventional Preloading cont. The principle of Conventional Preloading If the temporary load exceeds theload exceeds the final construction load, the excess refers to as surcharge load.
  • 9. Conventional Preloading cont. • The temporary surcharge can be removed when the settlements exceeds the predicted final settlement. • This should preferably not happen before the remaining excess pore pressure is below the stress increase caused by the temporary surcharge. • By increasing the time of temporary overloading, or the size of the overload, secondary settlement can be reduced or even eliminated.be reduced or even eliminated. • This is because by using a surcharge higher than the work load, the soil will always be in an over consolidated state and the secondary compression for over consolidated soil are much smaller than that of normally consolidated soil. This will benefit greatly the subsequent geotechnical design.
  • 10. B. Vacuum Preloading • Sometimes soft soil may be so weak that even a common 1.5 m embankment might cause stability problems. Then it can be suitable to use the method of vacuum preloading. • In 1952 Kjellman was the first who introduced vacuum preloading to accelerate consolidation. Invacuum preloading to accelerate consolidation. In vacuum consolidation the surcharge load is replace by atmospheric pressure. • In its simplest form the method of vacuum consolidation consists of a system of vertical drains and a drainage layer (sand) on top.
  • 11. Vacuum Preloading Conti…. • The common advantages of vacuum preloading are that there is no extra fill material needed, the construction times are generally shorter and it requires no heavy machinery. Moreover, norequires no heavy machinery. Moreover, no chemical admixtures will penetrate into the ground and thus it is an environmental friendly ground improvement method.
  • 13. Vacuum Preloading cont. Possible problems associated with vacuum preloading are: • To maintain an effective drainage system under the membrane that expels water and air throughout the whole pumping duration. • Keeping non-water saturated medium below the• Keeping non-water saturated medium below the membrane. • To maintain an effective level of vacuum. • To maintain a leak proof system in particular at the pumps / membrane connections and over the entire membrane area.
  • 14. Vacuum Preloading cont. • Anchoring and sealing of the system at the periphery. • Reducing lateral seepage towards the vacuum area.area.
  • 15. Principles of Preloading Figure illustrates schematically a vertical stress profile when a vacuum load (assuming 100 % efficiency) is applied to the ground surface in comparison with initial conditions and conventional surcharge. a) initial in situ conditions
  • 16. Principles of Preloading cont. b) conventional surcharge c) vacuum induced surcharge
  • 17. Vertical Drains • Preloading technique may not work sometimes alone due to a thick uniform soft clay layer or permeability of the clay is very low. • so time for precompression is very long and not practical or surcharge will be very high for reasonable waiting periods.reasonable waiting periods. • Because of its low permeability, the consolidation settlement of soft clays takes a long time to complete. To shorten the consolidation time, vertical drains are installed together with preloading either by an embankment or by means of vacuum pressure.
  • 18. Vertical Drains cont. • Therefore, the vertical drain installation reduces the length of the drainage path and, consequently, accelerates the consolidation process and allows the clay to gain rapid strengthprocess and allows the clay to gain rapid strength increase to carry the new load by its own.
  • 19. Vertical Drains cont. Preloading with vertical drains
  • 21. Types of Vertical Drains • Sand drains are basically boreholes filled with sand. As for the displacement type of sand drains, a closed mandrel is driven or pushed into the ground with resulting displacement in both vertical and horizontal directions. • The installation causes therefore disturbances, especially in soft and sensitive clays, whichespecially in soft and sensitive clays, which reduces the shear strength and horizontal permeability. • The low- or non-displacement installations are considered to have less disturbing effects on the soil. Drilling of the hole is done by means of an auger or water jets. In terms of jetting, however, installation is very complex.
  • 22. Types of Vertical Drains conti. • The installation of prefabricated vertical drains is also done by a mandrel and it is a displacement installation. The dimensions of the prefabricated drains are much smaller compared to sand drains and subsequently are the dimensions of the mandrel. Thus, the degree of soil disturbance caused by the size of the mandrel during installations is lower. by the size of the mandrel during installations is lower. • At the tip of the mandrel is detachable shoe or anchor made of a small piece of metal (given in following figure). Sometimes it might also be a piece of drain itself. The purpose of the anchor is to prevent soil from entering the mandrel and plugging it during penetration. It also keeps the drain at the desired depth as the mandrel is withdrawn.
  • 23. Some disadvantages of sand drains • To receive adequate drainage properties, sand has to be carefully chosen which might seldom be found close to the construction site. • Drains might become discontinuous because of careless installation or horizontal soil displacement during the consolidation process. • During filling bulking of the sand might appear which could lead to cavities and subsequently to collapse due tocould lead to cavities and subsequently to collapse due to flooding. • Construction problems and/or budgetary burdens might arise due to the large diameter of sand drains. • The disturbance of the soil surrounding each drain caused by installation may reduce the permeability, the flow of water of water to the drain and thus the efficiency of the system. • The reinforcing effect of sand drains may reduce the effectiveness of preloading the subsoil.
  • 24. Drain Properties • Equivalent diameter for band-shaped drains The theory of consolidation with vertical drains assumes that the vertical drains are circular in their cross-section. Since most of the prefabricated drains are rectangular in cross-section, the rectangular drain has to be converted into an equivalent cylindrical shape. That implies that the equivalent diameter has the same theoretical radial drainage capacity as the band-shaped drain. The equivalent diameter (dw) of a band-shaped drain with width (a) and thickness (b) as given below.
  • 25. Discharge Capacity The discharge capacity depends on the following factors: • Lateral earth pressure: By increasing lateral pressure, the filter passes into the core and subsequently decreases the discharge capacity due to a reduction of the cross-sectional area available for flow. • Large settlements: During consolidation, the ground will be subjected to large settlements. Thus, the drains tend to settle together with the ground which will result in bending of folding of the drain. • Clogging of drain: In the initial filtering process of flow from the soil• Clogging of drain: In the initial filtering process of flow from the soil through the drain filter, the displaced water will contain a small portion of fine particles. These may be deposited with the core channels and may lead to clogging of the drain. • Time: The discharge capacity may be reduced due to aging in the soil after installation, possibly due to biological and chemical activities. • Hydraulic gradient: The measured discharge capacity varies with different hydraulic gradients and is smaller when a higher hydraulic gradient is used. This might be due to the loss of flow energy as a result of turbulent flow at a high hydraulic gradient.
  • 26. Properties of the filter The filter has to meet the following requirements: • The permeability of the filter should be high enough not to influence the discharge capacity of the drain system. • On the contrary, the permeability of the filter should be low enough to retain fine soil particles. The soil particles might penetrate through the filter into the core, which eventually might be filled with soil and getcore, which eventually might be filled with soil and get clogged. • The filter needs to be strong enough to withstand high lateral pressure in order not to be squeezed into channel system of the core. • The filter should be strong enough not to break during installation, and • The filter should not deteriorate with time because this would reduce the discharge capacity of the drain.
  • 27. CONCLUSION • A system of prefabricated vertical drains(PVDs) combined with vacuum preloading is an effective method for accelerating soil consolidation. • It is clear that the application of PVDs combined with vacuum and surcharge preloading has become common practice, and is now considered to be one of the most effective ground improvement techniques. • Analytical and numerical modelling of vacuum preloading is still a• Analytical and numerical modelling of vacuum preloading is still a developing research area. There has always been a discrepancy between the predictions and observed performance of embankments stabilised with vertical drains and vacuum pressure. • Vacuum assisted consolidation is an innovative method which has recently, and successfully, been used for large scale projects on very soft soils in reclamation areas. The extent of surcharge fill can be decreased to achieve the same amount of settlement and the lateral yield of the soft soil can be controlled by PVDs used in conjunction with vacuum pressure.