GEOTECHNICAL ENGINEERING ECG 503 LECTURE NOTE 12 TOPIC : 4 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.

Hydraulic Methods and Objective of Vertical Drain and Preloading 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 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 0.29 nm aluminium or magnesium hydroxyl or oxygen oxygen silicon 0.26 nm Silicon Tetrahedron Aluminium Octahedron

Micro-fabric particles in natural clay. Dispersed Flocculated

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