软土地区CFG桩群孔效应引发的地表沉降  

Surface Settlement Caused by Borehole Group Effect of CFG Piles in Soft Soil

作　　者：郑刚[1,2] 王凡俊[2] 孙宏宾 程雪松[1,2] 雷华阳[1,2] 张涛[2] 

机构地区：[1]滨海土木工程结构与安全教育部重点实验室(天津大学),天津300072 [2]天津大学建筑工程学院,天津300072

出　　处：《天津大学学报（自然科学与工程技术版）》2017年第8期796-805,共10页Journal of Tianjin University：Science and Technology

基　　金：国家自然科学基金资助项目(51508382;41630641);中国博士后科学基金资助项目(2014M561186)~~

摘　　要：在软土地区CFG桩施工形成的大量空桩孔如不及时回填会产生群孔效应,造成地表沉降,进而威胁邻近建筑物、隧道及管线等基础设施的安全.本文基于某工程实测结果,利用有限元研究了单孔和多孔情况下引起的地表沉降情况及多孔叠加机理,提出了多孔合并法来解决实际工程中数量庞大的桩孔较难模拟问题,并对群孔效应引发周边严重沉降的工程进行了模拟分析.研究结果表明,单孔引发的沉降值主要受孔径影响,呈正相关;沉降最大值位置主要受孔深影响,呈线性正相关.孔心距较小时,空孔周边土体中水平和竖向上的土应力拱的相互影响与削弱导致每个空孔的内缩变形均大于单孔时的变形值,是导致群孔效应引发周边严重沉降的主要原因.群孔引发的沉降与孔数呈对数关系,孔数增大到一定值时沉降不再显著增长.所提出的多孔合并的群孔研究方法及合并转化系数?,为进一步研究群孔效应奠定了基础.A large number of hollow boreholes left in the soil strata during the construction of CFG piles can lead to the borehole group effect and cause the surface settlement in soft soil area,which threats the safety of adjacent buildings,tunnels and municipal pipes.Based on a case study,the surface settlements caused by single and group hollow boreholes and the mechanism underlying the effect of boreholes on each other were investigated by the finite element method（FEM）.To simulate the massive pile holes in practical engineering,a method of multi-hole merging is proposed.Additionally,the case was modelled by FEM using this method,and the settlements derived by the numerical simulation and field measurement were compared and analyzed.Thus the settlement mechanism is revealed.The results show that for the single borehole,the settlement value is mainly influenced by and increases linearly with the hole diameter.The distance between the maximum settlement position and the hole is mainly influenced by and increases linearly with the hole depth.The shrinkage of each hollow borehole becomes greater than that of the single hole because the horizontal and vertical stress arching surrounding each hole influences and destroys each other when the hole center distance is relatively small.It is an important mechanism for the borehole group effect.For the borehole group,the settlement increases logarithmically as the hole number increases,and when the hole number is larger than a certain value,the settlement remains unchanged.Furthermore,the method of multi-hole merging and the conversion coefficient ？ proposed in the paper can provide a reference for the further study on the borehole group ef-fect.

关 键 词：CFG桩 群孔 地表沉降 软土 

分 类 号：TU411[建筑科学—岩土工程]