Transcript No Slide Title

GEOTECHNICAL ENGINEERING
ECG 503
LECTURE NOTE 11
TOPIC : 4.0 GROUND
IMPROVEMENT TECHNIQUES
MARCH 2009
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
 Objective and Principles of Ground
Improvements
 Types of Ground Improvements
With Respect of Cohesionless and
Cohesive Soil
 Mechanical Methods and Objective;
Stone Column, Dynamic
Compaction, Vibrofloatation and
Vibro Compaction.
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
Stone Columns
vibrator makes a
hole in the weak
ground
hole backfilled ..and compacted Densely compacted
stone column
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
GEOTEXTILES