Experimental Evaluation of Stress Path of Weak Foundation Soil Reinforced with Recycled Plastic Pins

With the advancement of civilization, building structures on weak foundation soil has become essential nowadays. When structures are built on weak foundation soil, they are subjected to bearing failure and excessive settlement. Most of the conventional ground improvement techniques are expensive, and they use virgin materials. The use of recycled plastic pins (RPPs) is a low-cost solution that can reduce the environmental effect of using virgin material and enhance sustainable waste management systems. The objective of this study is to quantify the increase of the strength behavior of weak foundation soil reinforced by RPPs. RPPs having two different cross-sections (100 mm × 100 mm, and 150 mm × 150 mm) were installed in the field at different spacings. Since RPPs were driven into the soil, the surrounding in situ soil got displaced and compacted. Dynamic cone penetrometer (DCP) and soil penetrometer were used to evaluate the material properties of the in situ soil. The strength properties of the improved soil were determined by laboratory investigation and also using the correlation between the shear strength of soil and dynamic cone penetration index. It was observed that the shear strength of the reinforced soil increased significantly compared to that of the unreinforced soil due to particle densification. This indicates an upward shift of the failure line of the reinforced soil. On the other hand, being stiffer material, RPPs carried a higher load, and the soil between RPPs was subjected to less stress due to soil arching action. Therefore, the stress paths shift downward, and the factor of safety of the reinforced ground against failure increases.