Influence of reinforced cushion in PCC pile composite foundation

Based on the in-situ tests,the development of differential settlement and stress ratio between PCC piles and soil was obtained.The material and thickness of reinforced cushion had an effect on the differential settlement and stress ratio.Therefore,the deformability of cushion and the reinforcing effect of geogrid in cushion should be taken into account.Different laying technology of cushion,such as pre-tension of geogrid,would result in different growing modes of pile-soil stress ratio.The larger the tensile force of geogrid was in laying,the faster the pile-soil stress ratio would develop.Furthermore,the numerical analyses by use of the finite element method were also made to study the influence of the tensile strength and arrangement of geogrid on the pile-soil differential settlement and stress ratio.It was indicated that with the increase of tensile strength of geogrid,the more loads would be supported by piles,which led to increase the bearing capacity of the composite foundation,and the pile-soil differential settlement would be reduced.However,the influence of number of layers and laying place of geogrid,especially the laying place,is almost negligible.