Test and numerical simulation of the bearing characteristics of prebored grouted implantable piles

To investigate the bearing performance of prebored grouted implantable (PGI) piles, two sets of field axial load tests were conducted. These tests revealed the interfacial nonlinear mechanical behaviors between the inner precast concrete (PC) pile, grouted material, and surrounding soils. Hyperbolic and elastic-failure models were adopted to characterize the shear behaviors at the grouted material - soil and inner PC pile - grouted material interfaces, respectively. Based on these models, a series of three-dimensional numerical analyses was conducted to simulate the field tests. The results of these analyses indicated that the outer grouted material (e.g. cement mortar) effectively transferred the load borne by the internal PC pile to the surrounding soil. Additionally, this grouted material played a role in expanding the diameter of the internal PC pile. The interfacial resistance between the inner PC pile and outer grouted material was greater at both ends and lower in the middle. In contrast, the interfacial resistance between the grouted material and soil gradually increased with depth. It was also observed that the thickness of the outer grouted material should be maintained between 100 and 250 mm to effectively use the bearing characteristics of the inner PC pile and achieve a synergistic effect between the PC pile and grouted material.