针对目前双模式盾构在复合地层土-岩交界面进行掘进模式转换过程中掘进面稳定性研究中存在的问题，采用空间离散技术构建双模式盾构在穿越土-岩交界面过程中开挖面前方岩土体的二维破坏机制，利用该破坏机制和极限分析上限定理推导得到极限状态下土舱压力的目标函数，通过优化计算得到盾构机在穿越土-岩交界面过程中维持开挖面稳定所需的土舱压力上限解，并讨论不同参数对土舱压力及开挖面前方岩土体破坏模式的影响。在此基础上，基于可靠度理论建立土舱压力的可靠度模型，并给出复合地层中容许可靠度下维持开挖面稳定性最小土舱压力的建议值。结果表明：盾构机在穿越土-岩交界面过程中维持开挖面稳定所需的土舱压力随着盾构机与土-岩交界面距离的减小而减小；开挖面前方岩土体的破坏范围随着界面倾角的增大而增大。

To study the stability of the tunnel face for dual-mode shield machine excavated in a composite strata, a two-dimensional failure mechanism of the tunnel face was constructed by using spatial discretization technique. The objective function of the soil chamber pressure in the limit state was derived by using this failure mechanism and the upper limit theorem of limit analysis. The upper bound solution of the soil chamber pressure to maintain the stability of tunnel face during the shield machine pass through the interface of the soil/rock was obtained from optimization. Moreover, the influence of different parameters on the soil chamber pressure and the failure mode of the tunnel face were discussed. On this basis, based on the probabilistic theory, the reliability model of the soil chamber pressure was established, and the minimum soil chamber pressure which was used to maintain the stability of tunnel face in composite stratum with a tolerable reliability was given. Parametric analysis shows that the soil chamber pressure decreases as the distance between the shield machine and interface of the soil/rock shortens, and failure region in front of the tunnel face increases with the increase of the interface inclination angle.

U455.43

国家自然科学基金（51878074、52278395）；湖南省自然科学基金（2021JJ30714）；长沙理工大学研究生科研创新项目（CX2021SS25）