GEOTECHNICAL ENGINEERING
ECG 503
LECTURE NOTE 12
TOPIC : 4.0 GROUND
IMPROVEMENT TECHNIQUES
09 OCTOBER 2008
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
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
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