中文摘要：

深圳市某新建工程的超深基坑开挖深度达33.8 m,并在坑底里需施工直径为9.5m、桩长为32.0m的巨型桩群.该基坑距离运营地铁车站出入口仅5.65 m.为确保运营地铁线路的安全,在工程原施工方案的基础上,提出增设第5道支撑和加长止水帷幕的优化施工方案.采用三维有限差分软件FLAC3D对原施工方案和优化施工方案进行数值模拟.数值计算结果表明：采用优化施工方案,可以有效地减小地铁线路沉降、隧道相对变曲、两轨道横向高差、轨道竖向变形和轨道三角坑变形.在采用优化施工方案施工的过程中,进行地铁线路位移和沉降以及车站所在处地下水位的监测.监测结果表明：地铁线路沉降的实测值与模拟计算值基本吻合;其沉降基本控制在《城市轨道交通安全保护区施工管理办法》的规定范围内.表明优化施工方案对控制地铁线路沉降是积极有效的,能够确保地铁的运营安全.

英文摘要：

One new project＇s deep foundation pit in Shenzhen is 33.8 m,in the pit bottom,super large diameter pile group with the diameter of 9.5 m and the length of 32 m are to be constructed.The distance between the deep foundation pit and the station entrance of operation metro is only 5.65 m.To ensure the safety of operation metro and based on the original scheme,the optimized scheme with adding the fifth support and deepening the waterproof curtain to slightly weathered rock is proposed.FLAC3D numerical simulation is used to compare the original scheme and the optimized one.The results indicate that the optimized scheme can effectively reduce metro track settlement,tunnel relative deformation,two-line lateral height difference,vertical track deformation and track twist irregularity.During the construction by the optimized scheme,metro track displacement and settlement as well as the underground water level of station are monitored.The monitoring results show that the measured values of track settlement agree basically with those of numerical simulation.The settlement is controlled within the stated value in ＂Construction Management Method for the Safety Protection Zone of Urban Rail Transit＂,which demonstrates that the optimized scheme is effective and can ensure the safety for metro operation.