盾构开挖面三维曲面体破坏模型及支护力计算方法研究

Curved solid failure model and calculation method of supporting pressure for shield tunnel excavation face

针对盾构隧道施工开挖面极限支护力这一重要课题,提出一种新的半圆台和局部球体的组合曲面体滑动块模型。当前,楔形体极限平衡方法普遍采用估算滑裂面侧面摩擦力作为已知量来列平衡方程求取开挖面支护力,但因滑裂面侧面摩擦力影响因素很多,很难估算准确。利用曲面体模型的对称性,在求解开挖面支护力时,避开滑裂面摩擦力的估算,提高了计算精度。并进一步对隧道拱顶以上的半圆台曲面模型进行了受力分析,考虑了主应力偏转引起的侧压力系数变化,推导了滑裂面为空间曲面时土拱效应下土中竖向应力的解析解。最后通过算例分析验证了推荐模型的合理性。结果表明,推荐模型简单、有效且有实用价值,可广泛应用于隧道施工开挖面前方土体的稳定性分析。

A new three-dimensional curved solid failure model by combining semi-circular platform and partial sphere was proposed to calculate limit support force of shield tunnel excavation face.At present,wedge-shaped models were generally used to calculate the supporting force of excavation face by using limit equilibrium method,in which the lateral friction force of sliding face was estimated as a known quantity.However,it is difficult to estimate the lateral friction force accurately because the lateral friction force of sliding surface is affected by many factors.In this paper,the symmetry of the curved solid model was used to solve the support force of the excavation face,and the calculation accuracy was improved by avoiding the estimation of the lateral friction force of the sliding surface.Furthermore,the force acting on the semi-circular platform model above the tunnel vault was analyzed given consideration to the variation of the lateral pressure coefficient caused by the principal stress deflection,and the analytical solution of the vertical stress in the soil was derived considering soil arching effect when the sliding surface is a spatial curved surface.Then the rationality of the proposed model was verified through examples analysis.Examples analysis show that the proposed model is simple,effective and practical.It can be widely used in the stability analysis for shield tunnel excavation face.