干砂盾构隧道开挖面主动极限支护压力计算

隧道开挖面支护压力的合理选取是维持开挖面稳定性的重要条件，本文基于筒仓理论与三维楔形体计算模型，假设开挖面破坏区滑动块为一个由部分球体与半圆台组成的弧形楔形体，滑动块上部为半圆柱体.采用Terzaghi松动土压力与Rankine主动土压力计算方法和滑动块受力平衡，推导出干砂条件下开挖面主动极限支护力计算公式.由案例分析可知，该公式计算结果小于魏纲和三维楔形体模型计算结果，且更接近Chambon 离心模型试验结果，并针对计算误差探讨了该计算公式局限性因素.

Calculation on Active Limit Support Pressure of Shield Tunnel Excavation Face in Dry Cohesionless Soil

Reasonable calculation on the support pressure of tunnel face is important for tunnel stability. Based on the silo theory and the 3D wedge model， the sliding block ahead of the face was assumed as an arc wedge composed by part of a sphere and half a circular truncated cone; and the upper silo of the sliding block is assumed as half a cylinder. The active limit face support pressure on the excavation face in dry cohesionless soil was derived based on the equilibrium of the sliding block according to the equations of Terzaghi loose earth pressure and Rankine active earth pressure. The calculation results from the proposed equation are less than that from Wei Gang’s model and the 3D wedge model， but is close to the results by Chambon’s centrifuge model tests. The restrictions of this method was discussed through calculation error analysis.