A Case Study on Unreinforced and Geogrid-Reinforced Working Platform Design by Finite Element Method

Granular working platform for a tracked plant is a geotechnical problem where a relatively thin granular layer is placed over weak subgrade in order to support the tracked plant pressure. Geosynthetics are sometimes placed in between existing weak subgrade and granular platform in order to increase bearing capacity and/or to limit settlement. Although a number of past studies have addressed bearing capacity problems for shallow foundations using analytical, empirical, experimental and numerical approaches over several decades, there exists a research gap to model granular working platform for tracked plants as a multilayer bearing capacity problem using numerical procedure. In this study, various design approaches to size the thicknesses of working platforms are first reviewed and discussed. A two-dimensional (2D) plane strain finite element model (FEM) is then developed and used to analyse specific cases of unreinforced and geogrid-reinforced granular working platforms. The developed models are verified by benchmarking them with several existing methods available in published literature, and results are found to be in good agreements. The results of the parametric study are then used to develop design charts with non-dimensional parameters for a specific range of soil strengths encountered in field conditions. The design charts are in convenient forms to be used both to design the tracked plant working platform granular base thickness and to evaluate the bearing capacity of a rough rigid strip footing resting on a relatively stiff layer over a soft stratum. The results have shown that a thin granular base is sensitive to plastic deformation when load is applied resulting in membrane effect which causes the early development of the reinforcement tensile stress and the effective anchorage length for the reinforcement is around 0.8 m or 2.7 to 4.7B.