Drained and Undrained Response of Soft Clays Reinforced with Fully Penetrating Sand Columns

The work presented in this paper explores the effects of drainage and rate of loading on the load response of soft clays that are reinforced with sand columns. The inclusion of sand columns in soft clays has been widely used to increase the load carrying capacity of the clay, reduce the settlement, and control/reduce the generation of excess pore water pressure during loading. A comprehensive laboratory testing program was designed to further explore and quantify those effects. It consists of a series of consolidated undrained (CU) and consolidated drained (CD) triaxial tests conducted on specimens of Kaolin clay reinforced with sand columns of various diameters. The clay specimens had diameters of 7.1 cm and heights of 14.2 cm and were prepared from slurry. The sand columns had diameters of 2 or 3 cm and were installed in pre-drilled holes fully penetrating in the clay specimen. Tests were conducted at effective confining pressures of 100, 150, and 200 kPa. Results obtained from the laboratory testing program are presented and the effects of the various parameters which govern the load response of the sand column/clay composite are presented and discussed.