中文摘要：

桩土应力比是反映复合地基承载特性的重要参数之一,可反映复合地基的荷载传递和变形机制。做为一种新型桩,目前尚未得出统一的计算X形桩复合地基桩土应力比的公式。沉淀池、滤池等构筑物是典型的具有混凝土底板（刚性基础）的结构,刚性基础下桩复合地基的承载性能有别于柔性基础。故结合南京桥北污水处理厂地基处理工程做现场静载荷试验,应用有限元软件ABAQUS建立刚性荷载板下现浇X形混凝土桩复合地基的模型,模拟不同桩身弹性模量、桩周土压缩模量、桩长、褥垫层厚度和压缩模量等参数下现浇X形混凝土桩复合地基的桩土应力比,结果表明,桩身或褥垫层模量增大、桩周土体模量减小、褥垫层厚度减小、桩长等增加都能使桩土应力比增大;现浇X形桩复合地基桩土应力比理想值为20～25,此时桩身模量取10～20 GPa,碎石褥垫层的厚度为20～40 cm,模量为30～45 MPa。

英文摘要：

As one of the most important factors,pile-soil stress ratio can reflect the load transfer and deformation mechanism of composite foundation.Up to now,as a new pile,no uniform method has been found to calculate the pile-soil stress ratio for X-section pile.Sedimentation basin and filter chamber are typical buildings with concrete floor plate that is considered to be a rigid base.The bearing capacity of pile composite foundation under the rigid base is different from which under the soft base.The in-situ static load tests are carried out based on the foundation treatment project in Qiaobei sewage treatment plant.Besides,a finite element model is built to simulate the cast-in-place X-section concrete pile composite foundation under the rigid base by software ABAQUS.The pile-soil stress ratios are discussed considering some factors including elastic modulus of pile,compression modulus of surrounding soil,pile lengths,cushion thicknesses and compression modulus.The results reveal that the pile-soil stress ratio increases with the increasing of pile modulus,cushion modulus and pile length,while reduces with the increasing of modulus of surrounding soil and cushion thickness.The reasonable pile-soil stress ratio of X-section pile ranges from 20 to 25,corresponding to the pile modulus from 10 to 20 GPa,the cushion thickness from 20 to 40 cm,and the cushion modulus from 30 to 45 MPa.