Repeated Load Response of Encapsulated Granular Trench Supported Footings on Embankments

Geosynthetic encapsulated granular trenches (EGT) have found to improve the load carrying capacity of strip footings situated on weak soil under monotonic load. Granular trench is a two-dimensional plane strain variant of stone column. The EGT is formed by wrapping a geosynthetic around the granular trench. In the investigation reported herein, repeated load behaviour of EGT supported strip footings situated on earth embankments was studied. Repeated load tests were carried out on model strip footings resting on granular trenches with and without encapsulation. A cyclic hydraulic actuator with control and data acquisition facilities was used. River sand was used to prepare the embankment and 6 mm aggregate was used as the fill for the trench. Geogrid reinforcement was used for encapsulation. Non linear finite element simulations were carried out to arrive at the optimum dimensions of the EGT under monotonic loading. The optimum dimension thus obtained was used for repeated load studies. Influence of magnitude and frequency of repeated loading were investigated through experiments. Details of test setup, experimental programme, observations and results are discussed in the paper. It was found that the EGT system effectively improves the bearing capacity of footings situated on earth embankments under repeated loading.