考虑土体强度非线性的富水盾构隧道开挖面三维稳定性研究

Three-dimensional stability of excavation face of water rich shield tunnel considering seepage effect and nonlinear failure criterion

为了计算高水压条件下开挖面有效支护力,评估盾构掘进的安全性,在极限分析上限理论框架下,构建开挖面三维曲线圆锥主动破坏机构。首先,采用切线法将非线性强度准则线性化,并引入经验水头公式描述开挖面附近水头分布;其次,提出一种水平分层积分法来计算渗透力功率,建立考虑渗流效应的功率平衡方程;第三,求解盾构土仓内有效应力目标函数,采用序列二次优化算法优化目标函数,求得支护力的最优上限解;最后,通过对比,验证本文计算结果的合理性和正确性,分析非线性系数和水位高度对有效支护力的影响。研究结果表明:在渗流条件下,非线性系数和单轴抗拉强度对开挖面稳定性的影响不利,增大初始黏聚力有利于开挖面的稳定,水头差对支护力具有显著的影响。

In order to calculate the effective support pressure of excavation face under the condition of high-water pressure and to evaluate the safety of shield-driven tunnel,a three-dimensional curve cone failure mechanism was established in the framework of the upper-bound theorem of limit analysis.Firstly,the nonlinearity of soil strength was included by a tangential technique and an empirical hydraulic head formula was introduced to describe the distribution of hydraulic head around the excavation face.Secondly,a new horizontal layered integral method was proposed to calculate the seepage-induced work rate and the work-energy equation considering the seepage effect was created.Thirdly,the objective function of effective stress in the chamber of shield machine was derived and then the sequential quadratic optimization algorithm was adopted to optimize the least upper-bound solution.Finally,the rationality and correctness of the present results were validated by comparing with the literature.The influence of nonlinear coefficient and head difference on the effective support pressure was analyzed.The results show that under seepage condition,the influence of nonlinear coefficient and uniaxial tensile strength on the stability of the excavation face is unfavorable,the increase of initial cohesion is beneficial to the stability of the tunnel face,and the influence of head difference on the support pressure is significant.