Direct shear tests on geosynthetic-encased granular columns

The behaviour of geosynthetic-encased granular columns (EGC) under vertical loads is reasonably well understood. To date, very little research has been done to understand the behaviour of EGCs subjected to lateral loads. The main objective of this paper is to quantify the effect of encasement on the lateral load capacity of EGCs. Several direct shear tests are performed on granular columns with and without encasement in a shear box having plan dimensions of 305 × 305 mm. Tests are conducted at different normal pressures varying from 15 kPa to 75 kPa. Two different diameters of columns, three types of encasements and three different plan configurations are studied in this research work. The results from these tests are discussed in terms of the increase in the shear strength due to geosynthetic encasement and the strength envelopes for understanding the influence of the encasement. Different types of failures observed in the granular columns (with and without encasement) subjected to lateral load are also discussed.