Estimated Strength Properties of Soft Clay Lump Backfilled in a Pond Improved by Vacuum Consolidation Method.

Abstract

There were many abandoned ponds previous time which were filled by water in Bangkok ,Thailand. Nowadays, the abandoned pond are dumped fully by backfilled lump soil without pumping the water out. The soil used for backfill in most of the cases have high water content and low shear strength which was called Bangkok soft clay. The backfilled soft clay are lump soft clay about bucket backhoe shape. The backfilled lump soils are generally dumped quickly and hence the water can’t leak out of pond and stuck between inter lump void. The shear strength in the backfilled lump soils are generally low uniformly along the depth because of newly deposition. The analysis has been carried out in two parts to estimate the increase in strength of backfilled soil. Firstly, the increase in strength of backfilled soil after improving by vacuum consolidation method was estimated by in-situ test (Cone Penetration Test), laboratory test (Unconfined Compression Test) and theoretical analysis (Mesri and Khan, 2011). Secondly, various factors (i.e. environmental, surcharge load, service load, soil properties and ground water level drawdown in Bangkok) responsible for increase in strength of ground surface have been estimated.