By Dr. Heng Li [bshengli@polyu.edu.hk] Tel: 2766 5879

1. References

M P Moseley, Ground Improvement, Chapman & Hall

2. Learning Objectives

"Students should acquire basic methods used in stabilizing soil in construction."

3. Vibro Techniques

Suitable for non-cohesive soils with dry densities less than their maximum dry density. The vibrations will result in a rearrangement of their grain structure. The treated compacted soil is capable of sustaining higher bearing pressure.

4. Dynamic Compaction

Dynamic compaction improves weak soil by controlling high energy temping (dropping heavy weights on the ground surface to improve soils at depths).

5. Lime Stabilization

Lime columns can be used to improve the bearing capacity of soft clay and silt and to reduce settlements. In this method, the soft soil in mixed in situ with unslaked lime (CaO) by a tool shaped like a giant dough mixer.

The lime column's function is to drain in the soft soil, as the permeability of lime is higher than soil.

6. Cement Grouting

By injecting cement into soils, the weak soils can be strengthened.

7. In-situ Soil Mixing

The in-site mixing of soils and stabilizing agents such as cement, lime, and bitumen has been used in road construction for many years. To improve the soft ground, the mixing equipment penetrates to the specified depth and is afterwards withdrawn with simultaneous rotation. The layer to be improved is mixed twice while the hardening agent is added through a pipe during penetration and withdrawal.