Evolution of Polythene Sheet Performance on the Bearing Capacity of Soft Soil

Abstract

There are certain situations in the field compelling the engineers and scientists to enhance the bearing capacity of weak soils due to their lower strength to bear the superstructure loads. It is always preferred to use higher bearing capacity soils i.e., coarse-grained soils in foundations, but sometimes, it is unavoidable to use lower bearing capacity soils, i.e., soft soils due to unavailability of higher strength soils in the vicinity of the project area, and it is really expansive to borrow soils from remote areas. The soft soil undergoes excessive deformation on wetting and under the application of loads. In this situation, it is more feasible to improve the bearing capacity of soft soil, used in foundations. So, the objective of this study is to strengthen the soft soil foundations with partial layers of sand and polythene reinforcement. The potential benefits of polythene reinforcement were examined, conducting seven small-scale physical model tests and forty-seven numerical simulations with a square footing, sustained on medium dense sand and overlying soft clay. First, the data sets of numerical simulation were validated by comparison with the physical model test results, in which a good agreement was found. Finally, a detailed parametric study was executed using a finite element analysis to figure out the best alternative for number of reinforced layers (N), effective depth of reinforcement (d), thickness of top sand layer (Ds), in-between spacing of alternate reinforcements (h), top spacing of reinforcement (u) and reinforcement length (b). The test results showed that the soil system reinforced with 03 polythene layers provided the peak ultimate bearing capacity to that of other alternatives. Design recommendations are suggested on the basis of finite element model and the laboratory model studies for a square rigid footing supported on a reinforced granular fill – soft soil system.