2. keynote d.j.ketkar

8/16/2019 2. Keynote D.J.ketkar

http://slidepdf.com/reader/full/2-keynote-djketkar 1/24



9. PVD with Preload embankment

10 PVD with Vaccume preload

11 Jet Grouting



CASE 1 – REMOVING OF SOFT SOIL

Treatment – Excavation & Replacement

Excavated portion then filled with

engineered soil in layers by

compacting each layer to desired

density

Excavation carried out to the

depth of weak soilVery fast

Easy to construct

Very economic when good

engineered soil is available nearby

Process Advantages

Treatment – Placing of Loading Berms

Concept

• Counter loads • Counter loads

Suitable for soils

•Silty Clays /

clayey Silt•Silty Clays /

clayey Silt

Depth of weak

soil

• 2 – 3 m• 2 – 3 m

Additional Load acts as counterweight

resisting upward

movement

of

soil

and increases in‐situ strength of soil.

Additional load applied on the

sides of structureUseful when depth of treatment very small

Useful when excavation is not

possible

Process Advantages



Treatment – Basal Reinforcement

Concept

•Load

Redistribution•Load

Redistribution

Suitable for soils

•Silty Clays /

clayey Silt /

Loose sand

•Silty Clays /

clayey Silt /

Loose sand

Depth of weak

soil

• 2 – 3 m• 2 – 3 m

Place engineered soil in layers by compacting each

layer to desired density

Layer(s) of Geogrid / geotextile is laid at the

required level Easy to Execute

Fast

Process Advantages

Bearing Capacity ImprovementIn

Roads

/

Highways

– for

Separation

&

Reinforcement

Treatment – Dynamic Compaction

Concept

•Densification•Densification

Suitable for soils

•Silty Clays / clayey Silt / Loose sand


Depth of weak

soil

•2 – 3 m•2 – 3 m

Done in grid pattern and alternate passes given to achieve the required

densification

A

dead

weight

of

10‐

50

T

from

heights

of

5‐30 m applied by raising and dropping.

Involves applications of high levels of impact energy at the ground surface

Easy to Execute

Fast

Helps to reduce liquefaction

potential

Less expensive

Process Advantages



Treatment – Dynamic Compaction

S

S

First Pass

Second Pass

Mark Grid

First Pass of Impact

Second Pass of Impact

Ironing Pass – for shallow (Upper depth)



Ground Improvement Techniques for Deep Depths

(Depth of Weak Soil : 5 to 10 m)



Treatment – Sand WICK

Concept

•Load Transfer / Drainage


Suitable for

soils



Depth of

weak

soil

•10 – 25 m•10 – 25 m

Hole is drilled to the design depth and

filled up by sand with compaction

Can be installed by replacement or displacement method

Process



3. B CONSOLIDATING SOFT CLAY

Treatment – Band Drains PVD)

Concept

•Drainage•Drainage

Suitable for soils

•Silty Clays / clayey Silt

•Silty Clays / clayey Silt

Depth of weak

soil

•3 – 10 m•3 – 10 m

Depending

upon

spacing

of

band

drains,

consolidation period can be reduced to 3

to 8 months

Band drains reduces the drainage path Fast

Helps

to

reduce

liquefaction

potential

Process Advantages

Prefabricated Vertical Drains (PVD) with Preload

Consolidation Process – depends on the drainage path.

V

V

C

H T T

2

Reduces

Drastically

Load

Soil Solids & Water

(a) H = D

Single

Drainage

D

Double

DrainageLoad

Soil Solids & Water

D/2

D/2

(b) H = D/2

LoadWith

PVD

PVD @ Spacing ‘s”

(C) H = S/2



Band

Drain

Spacing 0.80

– 1.20

m

c/cGrid Pattern Triangular

Depth of Band Drain As per Soil Conditions

Geotextile (Optional) Woven / Non‐Woven

Sand Blanket 500 mm

Preload Height As per Design

Waiting Period As per Design

Typical Scheme CIDCO COASTAL ROAD JNPT

1

EGL

60.00

1.5

EGL

4.80

Band Drain at

0.80m c/c inTriangular

Band Drain 0.15 mabove EGL

0.300.50

EMBANKMENT

1

1.5

MURRUM

SAND MATWORKING PALTFORM

Woven Geotextile

Site

PreparationPVD

InstallationDrainage

BlanketGeotextile

Laying

Instrumentation

&

Preload

Embankment

Execution



12/3/2013 23

Soil Improvement with

vacuum systems

Principle of Vacuumconsolidation

12/3/2013 24

vacuum

atmospheric pressure

surcharge surcharge

Model for Vacuum consolidation



12/3/2013 25

0 50 100 150 200

100

600

300

400

500

200

700

Time in days

S e t t l e m e n t i n m m

Test Field Sweden

Wells

Wells withvertical drains

Drains

with Vacuüm

12/3/2013 26

Applications

• Stability Problems

• No space for shallow slopes orberms

• minimal allowable deformation

of subsoil (close to buildings)• Short construction period



12/3/2013 27

12/3/2013 28



12/3/2013 29

12/3/2013 30

Install PVD



12/3/2013 31

Connect Hoses to Vacuum Pump

12/3/2013 32

Placing Surcharge



12/3/2013 33

Vacuum + Surcharging

CASE 4

Treatment – VIBRO Stone Columns

Concept



Suitable for soils



Depth of weak

soil

•10 – 25 m•10 – 25 m

Hole is drilled to the design depth and

filled up by Stone with compaction

Installed by Vibro‐replacement method

Process



Stone Column

Involves partial replacement of weak soil with the stones (aggregates)

Stones are compacted by vibrations

General practice, to replace 6‐35 % of weak soil by stones.

Design loads vary from 20‐50 T

Installation creates a composite material of lower compressibility and higher shear

strength than the virgin weak soil

Involves partial replacement of weak soil with the stones (aggregates)

Stones are compacted by vibrations

General practice, to replace 6‐35 % of weak soil by stones.

Design loads vary from 20‐50 T

Installation creates a composite material of lower compressibility and higher shear

strength than the virgin weak soil



Stone Column Effects

Stone Column Benefits



Execution – Wet Top Feed Method

Site Preparation



CASE 6

Treatment – Jet Grouting

Concept

•Soil Modification

•Soil Modification

Suitable for soils



Depth of weak

soil

•10 – 25 m•10 – 25 m

Mixing and replacing it with cement slurry to form a hardened

cement mass

Injecting a continuous

selected

mix

of

cement

grout

at

high

pressure from a nozzle to cut into surrounding subsoil.

uses a high velocity jet stream to cut, remove and grout cement into the soil to form columns, panels or slabs

Process



SPOILSPOIL

SEQUENCE

1. Insertion of jetting tools into a drilled1. Insertion of jetting tools into a drilled

2. Discharging super‐high‐

pressure cement slurry

2. Discharging super‐high‐

pressure cement slurry

3. Replacing excavated spoil by cement slurry3. Replacing excavated spoil by cement slurry

1. Pre‐Jet Water at

150 bars Pressure

2. Jet Cement‐Slurry

at 200 bars Pressure

3. Cement‐Slurry will be mixed

with soil liquid Step1 then form

as CEMENT COLUMN

Step

by

Step

of

Cement

Column

Pre‐Jet with pressure 200 Bars Jet Grout with pressure 250 Bars



Pull Out Test

Deep

Excavation

in

Clay



Thank you

2. keynote d.j.ketkar

Documents