Effect of coir geocell and fill material on bearing capacity improvement of soft clay - an experimental study

The effectiveness of different fill material along with geocell reinforcement placed over soft clay beds has been studied by small-scale model tests in the laboratory. The test beds were subjected to mono tonic loading by a rigid square footing. Footing load and the corresponding deformations of the fill material or reinforced bed were measured during the tests. The influence of different fill material in isolation, fill material reinforced with planar coir geotextile layer, coir geocell and geocell with planar geotextile at the base of the geocell mattress on the overall performance of the system has been systematically studied through a series of tests. Substantial performance improvement has been obtained in terms of increase in the load carrying capacity and reduction in the settlement and surface heaving of the foundation bed was observed when fill material of fine to medium sand was reinforced with coir geocells. An additional layer of planar geotextile placed at the base of the geocell mattress further enhances the load carrying capacity and stiffness of the foundation bed. The improvement in bearing capacity with reinforced fill material having a grain size more than 4.75 mm is only marginal. An eighteen fold increase in the bearing capacity of the square footing can be obtained by providing geocell reinforcement along with a basal planar geotextile layer in the coarse aggregate bed underlying soft clay. Stiffening the outer layer of coir geocell with horizontal or vertical stiffeners will reduce the carrying capacity of the fill material, increases the settlement but no heaving will be produced.