GEOTECHNICAL ENGINEERING
ECG 503
LECTURE NOTE 12
4.0 GROUND IMPROVEMENT
TECHNIQUES
LEARNING OUTCOMES
Learning outcomes:
At the end of this lecture/week the students would
be able to:
 Understand natural slope and made engineered
soil slope assessment which include rainfall
induced failure and role of suction.
TOPIC TO BE COVERED
 Mechanical Methods and Objective;
Stone Column, Dynamic
Compaction, Vibrofloatation and
Vibro Compaction.
 Physical and Chemical Methods
and objective; Grouting and cement
column
 Hydraulic Methods and Objective of
Vertical Drain and Preloading
Vibrating Plates

for compacting very small areas

effective for granular soils
Smooth-wheeled Roller
Smooth Wheeled
Roller
Compacts effectively only to 200-300 mm;
therefore, place the soil in shallow layers (lifts)
Sheepsfoot Roller to Compact Clay Soils
Sheepsfoot Roller

Provides kneading action; “walks out” after compaction

Very effective on clays
Impact Roller to Compact the Ground
Impact Roller
 Provides deeper (2-3m) compaction. e.g., air field
Dynamic Compaction
- pounding the ground by a heavy weight
Suitable for granular soils, land fills
and karst terrain with sink holes.
Pounder (Tamper)
solution cavities in
limestone
Crater created by the impact
(to be backfilled)
Pounder (Tamper)
Mass = 5-30 tonne
Drop = 10-30 m
Vibroflotation
Suitable for granular soils
Practiced in several forms:

vibro–compaction

stone columns

vibro-replacement
Vibroflot (vibrating unit)
Length = 2 – 3 m
Diameter = 0.3 – 0.5 m
Mass = 2 tonnes
(lowered into the ground
and vibrated)
Vibroflotation
Vibroflotation
Blasting
For densifying granular soils
Fireworks?
Aftermath of blasting
Earthmoving Equipment
Large Excavator (see minivan on left for scale)
Grader for spreading soil
Bulldozer for spreading soil evenly
Loader
Backhoe
Crawler mounted Hydraulic Excavator
Rock Breaker
Filed Compaction
Different types of rollers
(clockwise from right):
 Smooth-wheel roller
 Vibratory roller
• Pneumatic rubber tired
roller
 Sheepsfoot roller
Big weights dropped
from 25 m, compacting
the ground.
Craters formed in compaction
GENERAL
BACKGROUND OF
SOFT CLAY
Malaysia Coastal Area – Not fully developed
Soft clay usually located around the coastal area
The soft clay have been a source of
difficulties for many years. The soft
soil can cause settlement which can
give a lot of problem and damage in
several way. This is the reason why
Malaysia’s coastal areas are not
generally developed
TWO DISTINCT ATOMIC
STRUCTURAL UNITS
hydroxyl
or oxygen
oxygen
aluminium or
magnesium
silicon
0.26 nm
Silicon Tetrahedron
0.29 nm
Aluminium Octahedron
Micro-fabric particles in natural clay.
Flocculated
Dispersed
Flaky
shape
Plate like
structure
ION EXCHANGE
Ground Improvements for Soft Clay
• Stone Column (Vibro-Replacement)
• Prefabricated Vertical Drain
• Cement Column
VIBRO-REPLACEMENT
(STONE COLUMN)
Vibro-Replacement
• Also known as stone column.
The technique are similar to
vibroflotation/vibrocompaction
except the granular fill
materials which used is sand
is replaced by gravel stone
sizes ranging from 50mm to
100mm
Soil
Layer
-Increase in density
- Increase in bearing capacity
- Radial drainage (help to improve settlement)
- Shear strength of soil improve
- Reinforcing the soil by applying rigid member
(stone column) inside the soil
Stone Columns
vibrator makes a
hole in the weak
ground
hole backfilled ..and compacted Densely compacted
stone column
PREFABRICATED VERTICAL
DRAIN (PVD)
CEMENT COLUMN
(CHEMICAL STABILIZATION)
APPLICATION OF STABILIZE
CLAY
GROUTING TECHNIQUE
EXAMPLE OF CASE STUDY
FOR GROUND IMPROVEMENT
METHODS ON SOFT CLAY
GEOTEXTILES
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ecg503 week 12 lecture note chp4