Improving the bearing capacity of marine clay using polyurethane columns

Abstract

Problematic soil such as marine clay causes structures or pavement to crack and collapse as marine clay possesses low bearing capacity. Therefore, ground improvement is usually conducted to improve the bearing capacity. Since the use of cement for strengthening weak soil is not environmental-friendly, the aim of this study is to improve the bearing capacity of marine clay using polyurethane (PU) columns. The properties of the marine clay collected from Batu Pahat determined were particle size distribution, Atterberg's limits, specific gravity, and compressibility were determined. A series of small-scale physical modelling was conducted with a tank's size of 500 mm x 500 mm x 200 mm. The 1:1 ratio of poly and isocyanate was injected into the cored hole for the column formation with the area improvement ratio was set as 12.6%. The loading process was conducted 1 day after column installation. Double tangent method from the stress-displacement curve was employed to determine the ultimate bearing capacity of the marine clay. The ultimate bearing capacity of the untreated marine clay was 50 kPa. In addition, the results showed that the ultimate bearing capacity of the marine clay increased with the length of the PU columns. A maximum improvement ratio of 220% was achieved for the end bearing PU columns. Comparing the improvement ratio with the published data showed that PU columns had a better performance than soil cement or deep mixing cement columns due to its lightweight and high strength. Therefore, the replacement of cement with PU is workable and sustainable in ground improvement method.