A presentation of the main ground improvement techniques

1. Mohammad Alhusein, Ph.D.
Managing Partner
1
www.superarc.net
A PRESENTATION OF THE MAIN
GROUND IMPROVEMENT
TECHNIQUES

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Soil Improvement : why bother when I can do piles ?
The school just after completion…
School Play ground
Original
ground
:
clay
Reclaimed
fill
… and 5 years later !
• Exemple 1: the classic
mistake
 Buidings only are taken care of

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Soil Improvement : why bother when I can do piles ? 2/2
LNG terminal, BONNY Island – NIGERIA
• Exemple 2: the classic design  Piles everywhere, whatever the cost
Soil conditions Soil Improvement
Solution
Conventional Solution
Piles and deep
foundations

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 Aims of soil improvement
 Reduce post-construction
settlements (total and differential)
 Increase the bearing capacity
and/or the stability
 Mitigate the risk of liquefaction
 Advantages
 Eliminates the need for deep
foundations
 Eliminates the need for soil
replacement
 Offers a global treatment rather
than an isolated treatment
 Well adapted to uniform loads (up
to G+5) over a large area
 Saves time
  Saves money !

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A comprehensive approach
 A specific technical solution for each project, adpated to :
 The structure and the loads
 The type of soils (granular, cohesive)
 The specifications
 A complete solution bringing the advantages of soil improvement and
including:
 Design
 Construction / Execution of the designed treatment (single or multiple
technique)
 Post-treatment quality control (PMT, CPT)
 A guarantee to achieve the targets (planning and specifications)
  Peace of mind for the general contractor / the client

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Densified soil
settle
ment
Reinforcement by inclusions
Inclusions
Direct action on the soil structure
Initial loose
or soft soil
Basic Principles of Soil Improvement

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Range of Techniques
By Hydraulic Modification
 CONSOLIDATION
methods
Vertical Drains
Vacuum
Consolidation
By Mechanical Modification
 COMPACTION methods
Dynamic Compaction
Vibro Compaction
By Inclusions  REINFORCEMENT methods
Semi-Rigid Inclusion
(cement grout etc.)
Controlled Modulus
Columns
Jet Grouting Columns
Dynamic Replacement
Vibro Replacement
(Stone Columns)
Natural Inclusion
(sand, stone, etc.)
Fine grained soil (silt and clay) Coarse grained soil (sand and gravel)

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Improvement technique suggestion based on soil type and depth of improvement
(Braiek, 2017)

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Dynamic Compaction
By Hydraulic Modification
 CONSOLIDATION
methods
Vertical Drains
Vacuum
Consolidation
By Mechanical Modification
 COMPACTION methods
Dynamic Compaction
Vibro Compaction
By Inclusions  REINFORCEMENT methods
Semi-Rigid Inclusion
(cement grout etc.)
Controlled Modulus
Columns
Jet Grouting Columns
Dynamic Replacement
Vibro Replacement
(Stone Columns)
Natural Inclusion
(sand, stone, etc.)
Fine grained soil (silt and clay) Coarse grained soil (sand and gravel)

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Dynamic Compaction – Concept
• Invention patented by Menard in 1969
• For soils with up to 30-35% fine content
• Versatile (soils, depth)
• Well adapted to large areas

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Dynamic Compaction – Range of action
Pounders
25 tons
35 tons
15 tons
23 tons

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Dynamic Compaction – How does it work ?
Combined action of:
 Vertical waves
 de-structuration
 Shear waves
 re-arrangement
 denser state

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Dynamic Compaction – Phasing of the energy transfer

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Dynamic Compaction – Key Features
For soils with up to 30-35% fine content
 More fines  The excess pore water pressure cannot
dissipate
 Dynamic Replacement
Versatile
Economical and fast
Well adapted to large scale projects
No cement
No aggregate
Real-time adjustment of the applied energy to the actual
ground conditions
 an effective and sustainable technique

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Dynamic Replacement
By Hydraulic Modification
 CONSOLIDATION
methods
Vertical Drains
Vacuum
Consolidation
By Mechanical Modification
 COMPACTION methods
Dynamic Compaction
Vibro Compaction
By Inclusions  REINFORCEMENT methods
Semi-Rigid Inclusion
(cement grout etc.)
Controlled Modulus
Columns
Jet Grouting Columns
Dynamic Replacement
Vibro Replacement
(Stone Columns)
Natural Inclusion
(sand, stone, etc.)
Fine grained soil (silt and clay) Coarse grained soil (sand and gravel)

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Dynamic Replacement – Concept
• Invention patented by Menard in 1975
• Derived from Dynamic Compaction
• For depths up to 5 – 6 metres
• Well adapted to large areas

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Dynamic Replacement – How does it work ?
Transition layer
Arching effect
 Stress concentration into
the pillars
 Existing ground relieved
from most of the load
Draining effect
 Positive effect on the
consolidation of the existing
soil during the construction
Uniform Load
Transition Layer

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Dynamic Replacement – Key Features
• For soils where DC is not applicable  sabkhas, etc.
• For depths up to 5 – 6 metres  for deeper treatment:
• Pre-excavation
• High energy
• Other techniques (stone columns, CMC)
• Economical and fast
• Well adapted to large scale projects
• No cement
• No strict specification for incorporated material (recycled demolition
material OK)
• Real-time adjustment on site (DC / DR) if required
 an effective and sustainable technique

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Dynamic Techniques – Can vibrations be an issue ?
Safe distance = 30m (or even 10m with a trench)

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The Pressuremeter – Quick overview

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PROPOSED SOLUTION – Testing, PMT principles
PMT No. 1
0
50
100
150
200
250
300
350
0 5 10 15 20 25
Pressure (bar)
Volume
(cc)
calibration
2 meter
Bearing Capacity is calculated from
the limit pressure
The modulus of deformation
is calculated from the
straight portion of the curve
• Reputable
• Reliable
• Simulates exactly the
loading conditions of a
footing/raft/tank
• The only test that goes to
failure  good knowledge
of the FOS
• Measure both:
• The bearing capacity
• The modulus of deformation
• Best way to check design
specifications

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PROPOSED SOLUTION – PMT – Typical curve
Pl
Ep

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REFERENCES – Marafiq IWPP Phase 2, Jubail, 2007
Area: 56,500m2
Power block, fuel tanks, buildings, roads
100 to 200 kPa bearing capacity
25mm (footings) to 50mm (tanks)
settlement
Soil: 5.5m of very loose silty sands

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REFERENCES – Shuaiba IWPP III (2006)
Area: 150,000m2
Evaporators, water tanks,
support buildings
Tanks (Ø110m) : 200kPa /
75mm
Other: 150kPa / 25mm
Soil: 6 to 10m loose silty sands

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REFERENCES – ADCOP MOT – Fujairah, 2009
Area: 700,000m2
7 tanks – tank diameter = 110m
220 kPa (hydrotest)
Settlements:
 Absolute: 100mm max
 Differential 1: 50mm max between
any 2 points on the shell
 Differential 2: 13mm per 10m max
on the shell
Soil
 soft soil excavated and replaced by
quarry run
 Final platform at +3 to +6 above
natural ground level
solution
 Work from the FPL
 Fast
 No need of engineered fill

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DC – Dredged Fill of New Corniche Road, Abu Dhabi (2003)

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Case study – King Abdullah University, Jeddah – 2007
Project challenges
 Very fast track project,
 Huge surface,
 No knowledge of where the
buildings will be built,
 Presence of Sabkha, large SI grid
Technical Specifications
 Ensure bearing capacity for 150
tons footings @ 200 kPa
anywhere on site,
 Minimize absolute settlement to
25 mm and differential
settlement to 1/500,
 Ensure non liquefaction
Concept
 Overall Soil Improvement
concept based on DC/DR
treatment
 Benefits: high speed / Global
treatment

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KAUST – Initial soil conditions  how to work with sabkha !

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KAUST – A typical example of DC/DR strategy
No, but
loose sand
Yes
Transition
layer > 2 m
Transition
layer < 2 m
Case A Case B1 Case B2 Case B3
DC DR
Sabkha
Subst. over
1 m + DR
HDR +
temporary
surcharge
Presence of Sabkha
No Deep Sabkha (ie sabkha till
max 5 m below WPL)
Deep Sabkha (ie sabkha till more
than 5 m below WPL)
Compressible layer
(from loose sand to Sabkha)
Working Platform
Engineered Fill
150 tons
TL

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KAUST – A successful challenge
As built quantities
 Originally less than 1,500,000 m2 to be improved in 8
months including mobilization,
 Major change:
 Drastic increase due to additional areas
 However no allowance in terms of planning
 Finally nearly 2,600,000 m2 (increase of 80%)
improved within the original schedule (8 months)

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KAUST – A new benchmark for DC/DR

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Vibro Compaction
By Hydraulic Modification
 CONSOLIDATION
methods
Vertical Drains
Vacuum
Consolidation
By Mechanical Modification
 COMPACTION methods
Dynamic Compaction
Vibro Compaction
By Inclusions  REINFORCEMENT methods
Semi-Rigid Inclusion
(cement grout etc.)
Controlled Modulus
Columns
Jet Grouting Columns
Dynamic Replacement
Vibro Replacement
(Stone Columns)
Natural Inclusion
(sand, stone, etc.)
Fine grained soil (silt and clay) Coarse grained soil (sand and gravel)

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Vibro Compaction – Procedure
 Possible deep
treatment (>20m)
 Strict criteria on the
original ground grain
size distribution
 Best suited for soil
with less than 12%
fines
 Onshore or offshore
 Variable grid of
application (specs,
soils, uniformity)

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Vibro Compaction – Examples
 Riga (2008)
 Port Botany (2008)

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Vibro Replacement
By Hydraulic Modification
 CONSOLIDATION
methods
Vertical Drains
Vacuum
Consolidation
By Mechanical Modification
 COMPACTION methods
Dynamic Compaction
Vibro Compaction
By Inclusions  REINFORCEMENT methods
Semi-Rigid Inclusion
(cement grout etc.)
Controlled Modulus
Columns
Jet Grouting Columns
Dynamic Replacement
Vibro Replacement
(Stone Columns)
Natural Inclusion
(sand, stone, etc.)
Fine grained soil (silt and clay) Coarse grained soil (sand and gravel)

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Vibro-Replacement – Top Feed method
Main advantage: deep treatment possible
Limitations
 Will not work in very sof soil (bulging)
 Agregate size restriction make it a more costly solution than
DR
 Top feed : integrity of the bottom part of the column can not
be guaranteed

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Vibro-Replacement – Bottom Feed method
Main advantages
 deep treatment possible
 Guarantee of a uniform column
 Dry method
Limitations
 Will not work in very sof soil (bulging)
 Agregate size restricton make it a more costly
solution than DR
1 –penetration with air 2 –supply and compaction
of stones
3 –completed
columns

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Vibro-Replacement – Equipment
Bottom Feed pendular system (30m) Bottom Feed + vertical guide on mast (15m)

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Controlled Modulus Columns (CMC)
By Hydraulic Modification
 CONSOLIDATION
methods
Vertical Drains
Vacuum
Consolidation
By Mechanical Modification
 COMPACTION methods
Dynamic Compaction
Vibro Compaction
By Inclusions  REINFORCEMENT methods
Semi-Rigid Inclusion
(cement grout etc.)
Controlled Modulus
Columns
Jet Grouting Columns
Dynamic Replacement
Vibro Replacement
(Stone Columns)
Natural Inclusion
(sand, stone, etc.)
Fine grained soil (silt and clay) Coarse grained soil (sand and gravel)

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CMC – Concept and procedure
A solution to the problem of bulging for stone columns
No surface spoil
Improved friction ratio between soil and inclusion

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CMC – How does it work ?

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CMC – Design

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CMC – Applications
Shaika Fatma Villa , UAE Adnec Access Ramp, UAE

64. CE 4321: Geotechnical Engineering Design 64
Jet Grouting
By Hydraulic Modification
 CONSOLIDATION
methods
Vertical Drains
Vacuum
Consolidation
By Mechanical Modification
 COMPACTION methods
Dynamic Compaction
Vibro Compaction
By Inclusions  REINFORCEMENT methods
Semi-Rigid Inclusion
(cement grout etc.)
Controlled Modulus
Columns
Jet Grouting Columns
Dynamic Replacement
Vibro Replacement
(Stone Columns)
Natural Inclusion
(sand, stone, etc.)
Fine grained soil (silt and clay) Coarse grained soil (sand and gravel)

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Jet Grouting – Procedure and applications
Suited to any type of
soils
Rotation  column
Fixed  curtain

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Jet Grouting - Equipment

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Jet Grouting – Example : Quay Wall
Base solution: Combi-wall, 27m height (!) with tie-back anchors
Ground improvement  Gravity wall
 no more tie-backs
 reduction of the pile diameter and thickness
 max horizontal displacement = 150mm

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Vertical Drains
By Hydraulic Modification
 CONSOLIDATION
methods
Vertical Drains
Vacuum
Consolidation
By Mechanical Modification
 COMPACTION methods
Dynamic Compaction
Vibro Compaction
By Inclusions  REINFORCEMENT methods
Semi-Rigid Inclusion
(cement grout etc.)
Controlled Modulus
Columns
Jet Grouting Columns
Dynamic Replacement
Vibro Replacement
(Stone Columns)
Natural Inclusion
(sand, stone, etc.)
Fine grained soil (silt and clay) Coarse grained soil (sand and gravel)

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Vertical Drains - Principle
σ=σ’+u

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Vertical Drains - Equipment

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MENARD Vacuum Consolidation
By Hydraulic Modification
 CONSOLIDATION
methods
Vertical Drains
Vacuum Consolidation
By Mechanical Modification
 COMPACTION methods
Dynamic Compaction
Vibro Compaction
By Inclusions  REINFORCEMENT methods
Semi-Rigid Inclusion
(cement grout etc.)
Controlled Modulus
Columns
Jet Grouting Columns
Dynamic Replacement
Vibro Replacement
(Stone Columns)
Natural Inclusion
(sand, stone, etc.)
Fine grained soil (silt and clay) Coarse grained soil (sand and gravel)

83. Vacuum Consolidation: is a technique to speed up the
consolidation process needed to be employed to meet the
land development timings.
Vacuum consolidation method: The Menard Vacuum
Consolidation method is designed for preloading/surcharging
and consolidating very soft and soft saturated soils of low
permeability. The method consists of installing vertical and
horizontal vacuum transmission pipes under an airtight
membrane and sucking the air below the membrane thus
imposing a partial atmospheric pressure on the soil. This
loading process creates an accelerated isotropic consolidation in
the soil mass. The vacuum method can be combined with a
conventional surcharge placed on top of the membrane, in
order to achieve the required degree of consolidation under a
given design load and within the allowed time frame. 83

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Concepts : Principally, a vacuum consolidation system
consists of a system of drains vertically installed from ground
surface into the treated soil mass to prescribed depth, a
surface drainage system including a granular medium (sand
mat) and horizontal drains, and collector pipes leading to a
vacuum pump system for transmission of vacuum to the soil
as well as discharging water and air out of the treated soil
mass. The vacuum treated soil mass is isolated from surface
by an airtight membrane and if required laterally protected
from leakage by cut-off-walls. Table 1 presents three typical
vacuum consolidation systems utilizing different types of
vertical drains.

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Menard Vacuum – Concept
Failure Surface
Vertical
Stress
No Failure
Vertical
Stress
Classical Surcharge Menard Vacuum Method
The Menard vacuum proposal included the main concept to create
a ‘dam’ against potential slip failure under high fill surcharge of
the adjacent wick drain trial areas.

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Menard Vacuum – Procedure

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Menard Vacuum – Application : Camau PP,
Viet Nam
• 15 to 17m of very soft
clay
• Specs: less than
100mm settlement
over 10 years
• 85,000m2 +70,000m2
• 24 months

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You have a problem of foundation… we
have solutions for:
Residential Development Plants Roads and Railways
Warehouses Tanks Ports and Airports

90. ‫إﺻﻐﺎﺋﻛم‬ ‫ﻟﺣﺳن‬ ‫ﺷﻛرا‬
THANKS
90