CFG桩不同施工方案对基坑周边环境的影响研究

Effect of Different CFG Column Installation Methods on the Adjacent Deep Excavation Support Structures

CFG桩施工完成后桩体强度的增长与混凝土龄期呈正相关的关系。CFG桩施工过程中,基坑支护结构内侧被动区土体被扰动呈流态型,早期桩体强度很低,对支护结构及周边环境产生诸多不利影响。利用数值模拟软件MIDAS GTS/NX对CFG桩沿基坑长边顺序施工和基坑短边跳打施工不同方案进行了三维模拟。两种方案计算结果的分析和对比表明,沿短边跳打施工时基坑壁水平位移和周边地表沉降的最大值较小,安全性可靠,且短边跳打施工与长边顺序施工工期仅相差一天。综合分析,短边跳打施工方案安全可靠,对周边环境影响小,经济效益高,选为最终施工方案。

The compressive strength increase of the cement-fly ash-gravel(CFG)columns after the installation is positively related to the age of the concrete in the CFG column.During the CFG column installation,the passive soil zone inside the excavated area is disturbed and has minimal strength.Further,the strength of the CFG column at its early age is low.These adverse factors induce negative impacts on the supporting structures and their adjacent environment.The different CFG column installation sequences along the deep excavation supporting structures,which are column installed one next to the previous column along the longer supporting side and the column installed by skip one column along the shorter supporting side,are simulated by the commercial finite element software MIDAS GTS/NX.The results indicate that,the CFG column installed by skip location along the shorter side has less horizontal deflection in the supporting structure and less ground subsidence behind the excavated area.Further,the skip column location installation has only one day loner than the other method,but it is more reliable and less disturbance to the adjacent environment.Therefore,the skip column location method was recommended as the actual construction installation plan.