A STUDY ON ENGINEERING BEHAVIOUR OF GEOSYNTHETICS REINFORCED SOIL

Abstract

The bearing capacity of a foundation reduces in case of cohesive soil with low to medium plasticity, which thus requires the proper solutions for significant improvement in the loadcarrying capacity of the foundation. Geosynthetics are an effective way of increasing the shear strength of the soil, which results in lesser settlement and higher load-bearing capacity of foundation hence giving a safe and economical solutions. On the other hand, Various civil engineering structures such as bridge abutments and embankments require the construction of foundations on sloping grounds, is significantly reduces the bearing capacity of the foundation. Geosynthetic reinforcements can also be a low-cost method of enhancing the bearing capacity of such foundations and act as settlement reducer. However, their increments are dependent on the location of the placement of the geosynthetics within the foundation. Hence, in this study, a number of reduced scaled laboratory tests were performed on footing resting on flat and slopping surface. Different parameters such as spacing of the top layer reinforcement (u), number of reinforcement layers (N), vertical spacing between reinforcements (h), effective depth of reinforcement (d), types of reinforcements, slope angle (β), the distance between the edge of the slope and the loading surface (D) have been analysed. The study showed a significant improvement in bearing capacity of the foundation with geosynthetics inclusion, although maximum improvements occurred at the point of optimum placement of geosynthetics. Also, the improvement in the bearing capacity increased until it reached saturation with the increment in the number of layers of geosynthetic, thus signifying the presence of an optimum depth of reinforcement. Strains developed during the testing were also measured using strain gauges bonded onto the geosynthetic, and it is observed that strain development in geosynthetic is interrelated to footing settlement which has a very low strain in reinforcement located beyond the distance 2.5B from the footing center, where B is the width of footing. Numerical simulation of experimental setup is done to calculate the bearing capacity vi and settlements. Numerical results were compared with experimental results. Computation of the analytical model based on the reduction factor revealed R2=0.96, thus signifying that this model can be used effectively for computation of the ultimate bearing capacity of reinforced foundations. A statistical regression model was presented, with a confidence level greater than 95%, which included the significant parameters necessary for computation of the ultimate bearing capacity of reinforced foundations. The proposed equation was in close agreement with the experimental results, and the multiple R2 values and the adjusted R2 values were obtained as 0.956 and 0.951 respectively for the proposed model in case of footing resting over slopping surface and the multiple R2 values and the adjusted R2 values were obtained 0.964 and 0.953 respectively in the case of footing over flat surface.