Strength and consolidation characteristics of clay with geotextile-encased sand column

Installing sand columns in clays is a common ground improvement technique used to treat soft soils, and the inclusion of geotextile to encase the sand column can further improve the performance of the reinforced clay composite. In this work, the shear strength and consolidation characteristics of clay, clay with an ordinary sand column (OSC) and clay with a geotextile encased sand column (GESC) were investigated by carrying out laboratory direct shear and oedometer tests to study the response of the reinforced clay composite under both lateral and vertical loading conditions. It was found that the OSC and GESC significantly increased the shear strength of the clay, mainly by improving the friction angle, with little impact on the apparent cohesion. Furthermore, the OSC and GESC reduced the compression index, swell index, and recompression index of the clay to some extent. The secondary compression indexes obtained from the reloading stage were lower than those from the initial loading stage, indicating that over-consolidated clay has a lower secondary compression index than normally consolidated clay. The coefficients of consolidation showed an upward trend as the effective consolidation stress increased. In addition, the compressibility and hydraulic conductivity tended to decrease with increasing effective consolidation stress.