饱和圆砾地层盾构隧道开挖面稳定性物理模型试验

Physical model tests on stability of shield tunnel face in saturated gravel stratum

通过开展3组饱和圆砾地层盾构隧道开挖面稳定性物理模型试验,研究了不同埋深条件下开挖面支护压力不足导致的渐进失稳破坏过程。通过分析大颗粒土滑移松动—裂隙出现—裂隙闭合过程表明,开挖面破坏过程中土体存在变形滞后效应,且该效应随隧道埋深变浅而减弱。对开挖面变形进行PIV精细化图像分析,得到其破坏模式类似于楔形体加筒仓体结构,楔形体倾角约为45°+φ/2。筒仓区土体松动由于存在滞后效应,可能导致开挖面破坏表现出突发现象。为准确预测极限支护压力,将传统楔形体模型改进为宽体楔形体模型,预测结果与试验结果符合较好。

To detect the stability of tunnel face with different depth in saturated gravel stratum,three reduced scale model tests were conducted,and the progressive failure process under insufficient support pressure was explored.According to the particle analysis,loosens of particle contact and the initiation and closure of crack were investigated,the results indicate that delayed deformation occurs and it can be weakened by decreasing the tunnel depth.Based on the PIV analysis,the failure mode of tunnel face is obtained,it shows a combination mode of a sliding wedge and an overlying silo,and the inclination of sliding wedge is about 45°+φ/2.Due to the delayed deformation of soil in silo,a sudden collapse mode of tunnel face may occur.In order to produce a precise prediction of limit support pressure,a modified wedge model is proposed,and the obtained results compare well with test results.