盾构法己成为城市地铁施工中一种重要的施工方法，由施工引起的地表沉降及地层移动规律是盾构隧道设计和施工中非常关心的问题之一。地铁隧道施工阶段及施工后期诱发的地表沉降是造成各种建、构筑物产生外观及功能上损害的主要原因，每年由此而造成相当大的经济损失。因此，研究盾构隧道施工引起的地面沉降及土体侧向位移规律是十分迫切的。 本文结合西安地铁隧道施工，运用三维显式有限差分分析软件FLAC3D，建立地铁盾构施工过程的模型，对开挖及变形进行仿真模拟，系统分析研究了盾构施工过程中引起的土体位移情况，以及对影响土体变形的因素如隧道埋深、注浆时间的及时性、土舱压力等进行了分析。通过数值模拟等研究，得出了一些有参考价值的结论： 地表沉降随着盾构的推进不断增大，盾尾后30m左右达到最大值，为17.1mm。地表土体横向水平位移随着开挖断面的不断进行其值不断增大，在开挖面后30m处趋于稳定；地表土体纵向水平位移当盾构逐渐靠近监测面时土体向盾构推进的反方向移动，当盾构通过监测面后，土体又逐渐向盾构推进的方向移动。注浆体所处状态和注浆时间是否及时对地表沉降值影响非常大，注浆不及时时，引起的地表最大沉降值是注浆及时状态下的2~5倍，故壁后注浆的及时性是盾构隧道施工中一个极其重要的环节。增大土舱压力对控制地表沉降所起作用有限，或者并不合适，反而使地表沉降增加许多。实际施工过程中，宜与原始土压力保持一致。 研究得出的地铁盾构施工地层沉降机理和规律为类似工程方案确定与施工组织设计，可提供一定的参考价值。

The shield driving method has been one of the main construction methods in the urban tunnel . The soil sedimentations and ground movements caused by shield tunneling are the problems highly concerned in the design and construction process of shield tunnel. Ground surface settlement induced by subway tunnel construction and post-construction is the main reason which cause kinds of buildings damaged in appearance and functions.Futhermore,it brought great economic losses every year.So, The research on ground surface settlement and soil lateral displacement induced by shield tunnel is very urgent. This paper ,combining Xi'an Subway Construction,adopts the FLAC3D as compute tool which is three dimensional explicit finite-difference program for enginneering mechanice computation and establish the model of metro shield construction process to simulate the excavation and deformation of tunnel.This paper analyses the discipline of ground movements induced by shield tunnel construction,as well as,analyses some factors affect ground settlement such as the time about grouting、soil pressure on cabin and the thick-ness of over-buried layer and so on.By the numerical simulation study,some useful conclusion as follows: Surface subsidence increases as the advance of shield and reach the maximum after the tail of the shield about 30m.Tts maximum is 17.1mm.The lateral horizontal displacement of ground mass increases as the advance of shield ,tend to stability after the tail of the shield about 30m.The longitudinal horizontal displacement of the monitoring point is opposite with moving direction of shield as the shield gradually close the monitoring point;after shield passed the monitoring point,it is identical with moving direction of shield. If grouting is not timely,the maximum of ground surface settlement is about 2 to 5 times of grouting in time.Grouting in time is a key factor to minish stratum loss.In order to control the ground settlement,increasing soil pressure in cabin only play a finite role ,or it is not appropriate at all,on the contratry,it can increase the ground settlement.So it shoud is consistent with original soil pressure. The subway shield construction ground settlement mechanism and law obtained from the reserch can offer the reference value for the similar project plan determination and construction organization plan