基于应力释放的盾构隧道开挖地表沉降分析

以沈阳地铁1号线隧道为例,利用有限元方法研究盾构施工引起的横向地表沉降问题。引入地层损失和地应力释放的概念,分别在不同地层损失率、不同地应力释放率条件下,建立有限元模型进行计算。根据实际施工时监测到的地表沉降值与有限元模拟的地表沉降值进行比较,发现地表沉降值与地层损失率和地应力释放率成正比,〖ＪＰ＋１〗并通过最大地表沉降值的对比确定了该路段施工引起的地层损失率为1.747%,引起的地应力释放率为74.071%。利用同样的方法,确定了10座城市隧道开挖过程中引起的地层损失率区间为0.5%~2%、地应力释放率区间为60%~80%,并将地层损失率为1.747%和地应力释放率为74.071%时的衬砌混凝土管片处的最大弯矩与无地层损失、无地应力释放率模型管片处的最大弯矩值进行对比,可以发现最大弯矩值有明显的减小,分别减小了76.16%和71.82%。且2种方法得到的弯矩值非常接近,可以认为地层损失率模型和地应力释放率模型是等效的。

Analysis on Surface Settlement Induced by ShieldTunnelingBasedon Stress Release

The transverse surface settlement induced by shieldtunneling of Shenyang Metro Line 1 is analyzed by finite element method. Theconcepts of ground loss and ground stress release are introduced, and thefinite element models under different ground loss rates and ground stressrelease values are established. The comparison results between monitoredsurface settlement and simulated values show that the surface settlement isproportional to the ground loss rate and the ground stress release rate. Andthen, by comparing the maximum settlement value of the monitored data andsimulated values, it is determined that the ground loss rate caused by theconstruction is 1.747%, and the ground stress release rate is 74.071%.Similarly, it is determined that the ground loss rate in 10 cities caused bytunnel construction ranges from 0.5% to 2% and the ground stress release rateranges from 60% to 80%. Finally, the maximum bending moment at the liningconcrete segment of the FEM model with the ground loss rate of 1.747% andground stress release rate of 74.071% is compared with that without ground lossand ground stress release, and the comparison results show that the maximumbending moment value significantly reduces by 76.16% and 71.82%, respectively.The bending moment values obtained by the two methods are basically the same,which indicates the equivalence of ground loss rate model and ground stressrelease model.