不同本构模型对浅埋暗挖隧道施工引起地层扰动分析

Analysis of Ground Disturbance Caused by Shallow Tunnel Excavation UsingDifferent Constitutive Models

为了研究不同本构模型对浅埋暗挖隧道施工引起地层扰动的影响,本文基于FLAC3D软件,将莫尔库伦(Mohr-Coulomb,MC)本构模型以及Peck公式计算隧道开挖引起的地表处地层沉降进行对比,结果表明,与Peck公式的计算结果相比,MC模型的计算结果在隧道中心线处的沉降量较小,且在远离隧道中心处的地层出现明显隆起。在此基础上,分析了发生隆起的原因,提出由于隧道下方的回弹土体受到刚度较大的衬砌的约束,从而引起地面产生隆起的假设,并在降低支护结构的刚度条件下,证明了该假设的准确性。通过进一步采用MC模型和修正剑桥(Modified Cam Clay,MCC)本构模型进行对比计算分析,发现MCC模型计算在地表各处的沉降量与Peck公式计算结果基本吻合,均大于MC模型的预测,而且MCC模型能避免地表非真实隆起的产生。可见,相较于MC模型,MCC模型更适于软土地层浅埋暗挖隧道的地表沉降预测。

In order to study the influence of different constitutive models on stratum disturbance caused by shallow underground tunnel construction.This paper based on the FLAC3D,first compares the Mohr-Coulomb(MC)constitutive model and Peck formula to calculate the ground subsidence caused by tunnel excavation,which shows that the settlement of MC model is smaller at the center line of the tunnel being compared with the calculation results of Peck formula,and there is an obvious uplift in the stratum far from the center of the tunnel.On this basis,the cause of uplift is analyzed,and the assumption that the ground uplift occurs because the rebounding soil under the tunnel is constrained by the rigid lining is put forward.under the condition of reducing the stiffness of the supporting structure,the numerical calculation of the MC model proves the accuracy of the hypothesis.Furthermore,using the MC model and the Modified Cam Clay(MCC)constitutive model for comparative calculation and analysis,it is found that the settlement calculated by the MCC model is basically consistent with that calculated by the Peck formula,which is larger than that predicted by the MC model.Moreover,the MCC model can avoid the unreal uplift of the ground surface.It is found that compared with the MC model,the MCC model is more suitable for the prediction of surface subsidence of shallow underground tunnels in soft soil.