Upload
lingamkumar
View
218
Download
0
Embed Size (px)
Citation preview
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 1/24
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 2/24
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 3/24
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 4/24
9. PVD with Preload embankment
10 PVD with Vaccume preload
11 Jet Grouting
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 5/24
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
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 6/24
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
•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
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 7/24
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)
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 8/24
Ground Improvement Techniques for Deep Depths
(Depth of Weak Soil : 5 to 10 m)
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 9/24
Treatment – Sand WICK
Concept
•Load Transfer / Drainage
•Load Transfer / Drainage
Suitable for
soils
•Silty Clays / clayey Silt / Loose sand
•Silty Clays / clayey Silt / Loose sand
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
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 10/24
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
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 11/24
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
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 12/24
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
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 13/24
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
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 14/24
12/3/2013 27
12/3/2013 28
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 15/24
12/3/2013 29
12/3/2013 30
Install PVD
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 16/24
12/3/2013 31
Connect Hoses to Vacuum Pump
12/3/2013 32
Placing Surcharge
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 17/24
12/3/2013 33
Vacuum + Surcharging
CASE 4
Treatment – VIBRO Stone Columns
Concept
•Load Transfer / Drainage
•Load Transfer / Drainage
Suitable for soils
•Silty Clays / clayey Silt / Loose sand
•Silty Clays / clayey Silt / Loose sand
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
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 18/24
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
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 19/24
Stone Column Effects
Stone Column Benefits
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 20/24
Execution – Wet Top Feed Method
Site Preparation
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 21/24
CASE 6
Treatment – Jet Grouting
Concept
•Soil Modification
•Soil Modification
Suitable for soils
•Silty Clays / clayey Silt / Loose sand
•Silty Clays / clayey Silt / Loose sand
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
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 22/24
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
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 23/24
Pull Out Test
Deep
Excavation
in
Clay
8/16/2019 2. Keynote D.J.ketkar
http://slidepdf.com/reader/full/2-keynote-djketkar 24/24
Thank you