Composite Piles Foundation Settlement Analysis Based On Foundation-Structure Interaction

For the piles-foundation, the general design consider that the piles bear all the load from the superstructure, ignore the contribution from soil between the piles, in fact, for the pile foundation, because the piles group effect, and the interaction between piles and soil, piles and piles, makes the contribution for upper load from soil between the piles played a negligible influence. This thesis established a single pile, piles group, and a frame structure finite element model, study the design of settlement of the optimal control of composite pile foundation. Analyzed the whole frame 3D-model and adjust the stiffness of composite piles (pile length, pile diameter, pile spacing, raft thickness, variable stiffness of raft, etc.) to study the top settlement and differential settlement of the composite piles.The main outcomes are as follows:(1) This content used ADINA to analysis single pile under concentrated load found that the side friction resistance on pile developed from top to bottom gradually with the growing load. The soil bears load through the production of relative displacement between the pile and soil. By changing the length and radius of piles, found that increasing these parameters can reduce the settlement of pile cap.(2) Through finite element analysis of piles, found that to the friction-pile, increase the length of pile reasonably can not only to reduce subsidence, also can reduce the difference settlement significantly and save more materials than only change the diameters. Increase the length of pile can improve the bearing capacity of soil, but not very more. Soil of composite pile-foundation can bearing more load than conventional piles, and the bearing participation of soil increased significantly when the distance of piles is more than six times in composite pile-foundation.(3) Taking the interaction between composite pile-foundation and superstructure into consider to analysis the whole 3D frame structure model and several influential factors of composite pile foundation subsidence. Discovery that changes lengths, diameter of piles can reduce the settlement significantly. But increase the raft thickness can not reach so great effects.(4)At last of the content, according to different pile numbers, distance, diameter, raft stiffness of pile foundation, to layout optimized project of pile-foundation, this project reduced material consumption to get less subsidence and different settlement. Realize the economic and safety of pile design, the maximum different settlement is only 4mm, completely accord with the requirement of soil-foundation design standard.