The study of buoyancy behaviour of polyurethane foam as a ground improvement by constant rate strain test

Abstract

The buoyancy of lightweight polyurethane (PU) foam as a ground improvement is of important aspect to be investigated to ensure the stability of the founded structure. Constant Rate Strain test (CRS) was carried out to evaluate the buoyancy behavior of PU foam in water and to determine the effect of different water content of the marine clay to the settlement and uplift in short term undrained condition. The percentage thickness of PU foam to soft clay layer and water varies from 10% to 80%. The buoyant force of PU foam to immerse at the water surface depends on the thickness of PU foam that displaces the water. On top of that, water content in the soil has a crucial effect on the buoyancy of PU foam. For PU foam partial replacement on water, the downward displacement is very less compared to the settlement for PU foam partial replacement on marine clay soil due to higher buoyant force produced in the earlier condition. However, the settlement for improved condition of marine clay reduces significantly compared to the condition of existing condition. In addition, the reduction in soil weight as part of the soil is replaced with lightweight PU foam assist to reduce the overburden load imposed on the soil. Therefore, settlement reduces significantly with the increase in PU foam thickness. The verification of the buoyancy test results was done using finite element model PLAXIS 2D.