Interaction Analysis Of Raft And Composite Foundation With Rigid-flexible Piles

When the bearing capacity of natural foundation can’t meet the requirements of thebuilding, the foundation must be reinforced or using pile foundation to improve it. It is agood way to form the composite foundation by enhancing soil or replacing parts whichachieved the fact that natural soils and the enhanced parts working together to shareload. With the increased of foundation treatment technology and the development of thecomposite foundation theory, a new composite foundation appears which calledrigid--flexible pile composite foundation.Both rigid pile and flexible pile are used in the rigid--flexible pile compositefoundation. Rigid pile、flexible pile and soil between piles work together to withstandloads. The soil is too soft to bear loads. Flexible piles compensate the bearing capacityof soil between piles and improve the bearing capacity of the soil. Rigid piles not onlyprotect flexible piles，but also bear a larger part of loads and play an important role incontrolling settlement. Rigid--flexible pile composite foundation makes full use ofbearing capacity of its parts，reduces the engineering cost, and thus has a strongapplying prospects.Firstly，the parts of rigid--flexible pile composite foundation and the function ofthem are introduced in this paper，stress in piles and soil are discussed，the method ofcalculating composite modulus are compared to calculate settlement value. Secondly,the basic equations of raft and composite foundation working together is established bydiscussing raft analysis model and interaction relations between piles and soil. To studythe influence of its parts, the model of raft basis and rigid--flexible pile compositefoundation is established based on ANSYS software. By comparing the result ofcalculation，the influence of various parameters on the composite foundation arediscussed.Conclusions are drew as follows by this paper: Rigid pile modulus has littleinfluence on settlement but change the distribution of stress. The growth of flexible pilemodulus reduce differential settlement and change the ratio of each part. The influenceof raft modulus on settlement and stress distribution can be ignored, but the growth ofraft thickness increase its bending capacity and reduce differential settlement. Theexistence of cushion improve the distribution of stress, the growth its modulus reducesettlement but make the rigid piles bearing more loads. These rules can be used in actualproject to make this composite foundation get better used by selecting reasonable pile distribution and parameters number depends on the requirement of the building inbearing capacity and settlement.