Abstract:
Problematic soils, specifically soft clay, is widespread in Southern Punjab, Pakistan. These soils generally undergo excessive deformation on wetting and under the application of load due to their lower bearing capacity. Different researchers have been employing physical, chemical, and mechanical stabilization techniques to improve the performance properties of these soils for their efficient use. However, one of the most simple and efficient approach is to replace the soft soil with higher strength materials, i.e., coarse grained soil, but sometimes this approach is not workable due to unavailability of high strength materials at the project site. So, in this situation, the strength of soft soil can be increased using certain reinforcing materials, such as geo-membrane, geo-grid, geo-textile, geo-net, geo-cell, and others. Several studies have been conducted in this regard so far, but there is no mention to use polythene sheeting as reinforcing materials at any level in the present research. Polythene sheeting works as a confinement agent in soft clay, distributing the applied load to larger area, which consequently increases the bearing capacity of soft soil, and which is more likely due to uniform stress distribution within the foundation strata. So, the novelty of this research work involves investigating the performance of polythene reinforced soft soil system for closely spaced isolated footings with different combinations of their spacing to width ratios (S/B), and also for scaling effects. Regarding this, several physical and numerical simulation models were developed to attain the set objectives. The test results show that the interfering footings provide a bearing capacity of 67, 97 and 120 kPa, for only soft clay, sand reinforced soft clay and polythene-sand reinforced soft clay foundations, respectively. For closely spaced footings, the bearing capacity of polythene-sand reinforced foundation gradually increases with an increase in S:B (spacing: width ratio) up to 2.0, providing maximum bearing capacity of 145 kPa for model dimensions of 5B, which is about 7% less than that of model dimensions of 9B. Furthermore, closely spaced footings provide 32% more bearing capacity than isolated footings. Finally, a criterion of 9B is suggested for scaling effects of two closely spaced footing as a design recommendation.
