考虑土体剪胀性的富水盾构隧道掌子面支护反力非线性上限解

Upper bound solution of supporting pressure of shield tunnel faces considering soils dilatancy and the pore water under the nonlinear failure criterion

考虑土体剪胀性和孔隙水效应,在非线性破坏准则下研究盾构隧道掌子面的稳定性。利用极限分析上限法构建盾构隧道掌子面的对数螺旋曲线破坏机构,根据虚功率原理推导掌子面支护反力的解析解,利用序列规划算法得到了支护反力的最优解。研究结果表明,假定土体服从相关联流动法则,会明显低估支护反力,相对误差可达到29%。不考虑孔隙水效应,会显著低估支护反力,相对误差可达到56%。此外,土体剪胀系数以及孔隙水压力系数对掌子面的破坏范围也有显著影响。建议在计算盾构掘进推力时,应该考虑土体的剪胀性、破坏准则的非线性以及孔隙水效应,否则会造成结果严重偏小而导致掌子面发生坍塌破坏。

The stability of shield tunnel faces was investigated with the nonlinear failure criteria considering the pore water effect and dilatancy of soils. A logarithmic spiral curve failure mechanism of shield tunnel faces was constructed by using the limit analysis method. The analytical solution of support pressure was derived according to the virtual power principle. The optimal solution of support pressure was obtained by the sequence programming algorithm. The results show that if soils are assumed to obey the associated flow rule, the support pressure will be underestimated obviously, whose relative error can reach 29%. Similarly, if the pore water is not considered, the relative error of support pressure will be to reach 56%. In addition, the dilatancy coefficient of soils and the pore water pressure coefficient also have a significant impact on the failure scope of tunnel faces. It is suggested that soil dilatancy, nonlinearity of failure criterion and pore water effect should be taken into account to solve the driving force of shield, otherwise the results would be too small to cause collapse of tunnel faces.