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Granular piles, either ordinary or encased with geosynthetic materials are being extensively used as one of the ground improvement techniques, depending on the strength of the adjoining soil. The optimum granular pile (GP) length is still a matter of research, even though the approach is widely established in the literature. In the present study, a thorough and detailed parametric analysis has been carried out to ascertain the optimum length for ordinary and encased granular piles using a 2D axisymmetric finite element model. The soil behaviour has been modelled with the linearly elastic perfectly plastic Mohr-Coulomb failure criterion constitutive model. The parameters considered in this study are area replacement ratio, encasement stiffness, soil properties, infill material properties, and crust layer thickness. The findings revealed that the parameters with the greatest influence on the optimum length are the area replacement ratio, encasement stiffness, surrounding soil strength properties, and friction angle of the infill material. For encased granular piles, the optimum length was often found to be longer than ordinary granular piles. It was found that the optimum length for ordinary and encased GP ranges between 0.8-2.12 and 1-2.75 times of footing diameter (D), respectively. Through this study, an effort has also been made to investigate how the aforementioned parameters affect the radial bulging of the end-bearing GP. The upper section of 0.5-1.5D showed excessive bulging in each case. Additionally, the optimum encasement length was determined, and it was found that increasing the encasement length beyond 1.5D results in minimal improvement. Furthermore, a multiple regression analysis was employed to establish the correlation between the optimum length of GP and potential influencing factors.

来源平台：INTERNATIONAL JOURNAL OF GEOSYNTHETICS AND GROUND ENGINEERING