西安地区砂层地基上PHC管桩和CFG桩的应用分析  

Application analysis of PHC pile and CFG pile on sandy ground in Xi’an area

作　　者：丁小伟 高军程 李胜利 DING Xiao-wei;GAO Jun-cheng;LI Sheng-li(China Coal Xi’an Design Engineering Co.,Ltd.,Xi’an 710054,Shaanxi,China;China Vanke Co.,Ltd.,Shenzhen 518000,Guangdong,China)

机构地区：[1]中煤西安设计工程有限责任公司,陕西西安710054 [2]万科企业股份有限公司,广东深圳518000

出　　处：《地基处理》2023年第6期498-505,共8页Journal of Ground Improvement

摘　　要：西安渭河阶地地表以下约20 m深存在密实砂层,高层建筑能否选用以该层为桩端持力层的中短桩基础是设计面临的问题。结合同一场地两栋相同百米住宅楼的地基设计,通过方案分析、地基承载力和变形计算、载荷试验,采取调整筏板尺寸和沉降后浇带的位置,使结构重心与筏板平面形心重合等措施,选择基底下浅层密实中细砂层为桩端持力层,两栋楼分别采用11 m长PHC管桩和12 m长CFG桩复合地基,避免了该地区常用的长桩穿越砂层的困难和质量问题。结构封顶后的沉降观测数据结果验证两种方案可行,得出PHC开口管桩可利用土塞效应,其实际竖向抗压承载力比规范估算值提高约36%,管桩实际沉降量约为CFG桩的一半,且沉降稳定周期短,CFG桩复合地基采用Boussinesq解答分层总和法,计算沉降量与实测值差异不大。本工程充分利用地质条件,选择中短桩地基处理,节约了造价和工期,对类似场地的工程有借鉴作用。There exists a dense sand layer about 20 meters below the surface of the Weihe River terrace in Xi’an.The critical design consideration for high-rise buildings revolves around the choice of a medium short pile foundation with this layer serving as the end-bearing layer.Based on the foundation design for two identical 100 meter residential buildings on the same site,a series of measures were taken,including scheme analysis,computation of foundation bearing capacity and deformation,and loading tests.These measures included adjustments to the raft dimensions and the positioning of the post-settlement pouring strip to align the center of gravity of the structure with the centroid of the raft.A relatively shallow layer of dense to medium-fine sand beneath the foundation was designated as the end-bearing layer for the piles.Consequently,the two buildings were erected using 11 meter long PHC pipe piles and 12 meter long CFG pile composite foundations,effectively mitigating the difficulties and quality concerns typically associated with long piles traversing sand layers commonly used in the region.Post-structure completion settlement observation data validated the viability of both approaches.The findings show that PHC open pipe piles can effectively leverage the plugging effect,leading to an actual vertical carrying capacity approximately 36%higher than the value estimated in the specifications.The observed settlement of pipe piles is approximately half that of CFG piles,accompanied by a shorter settlement stability period.The CFG pile composite foundation utilizes the Boussinesq solution layered summation method,resulting in calculated settlement values closely matching the measured data.This project strategically capitalizes on geological conditions,choosing medium short pile foundation solutions to achieve cost savings and expedited construction,offering valuable insights for comparable site projects.

关 键 词：高层建筑 中短PHC桩 中短CFG桩 密实砂层 沉降观测 造价和工期 

分 类 号：TU473[建筑科学—结构工程]