深埋软岩隧道不同施工工法力学效应分析

Mechanical Response of Deep-buried Tunnels through Soft and Cracked Rock Mass under Different Excavation Methods

针对穿越软岩地段深埋隧道施工易坍塌的状况,在支护结构类型和参数一致的情况下,采用有限差分程序FLAC3D分别对四种工法(全断面法、台阶法、预留核心土法以及单侧壁导坑法)下隧道的掘进过程进行了三维数值模拟。分析了洞周围岩和支护结构在各种工法下的力学响应规律,并重点探讨了洞周围岩特征点位移、掌子面稳定性以及支护结构受力等效应。根据计算结果对上述四种工法进行了优选,并得出以下结论:从围岩变形及受力方面分析,单侧壁导坑法最优;预留核心土法更适合于深埋软岩隧道的施工;高应力大变形条件下,仰拱处变形应作为围岩稳定判据的关键因素之一;深埋隧道开挖过程中,竖向应力对支护结构影响较强,水平应力对支护结构影响较弱。

The study focuses on the problem that weak surrounding rock of a deep-buried tunnel tends to collapse during the process of excavation,and utilizes Finite Difference Method（FDM） software package FLAC3D numerically in three-dimensional to simulate the construction process of the tunnel with four kinds of excavation schemes which are full-face method,bench method,ring-opening and core-retaining excavation method and center-diaphragm method,with the condition of same supporting structure type and parameters.The mechanical responses of surrounding rock and supporting structure under the four kinds of excavation schemes are analyzed.In particular,more attention is paid to the displacement pattern of the target section,stability of the tunnel face and stress distribution of the supporting structure.Based on the simulation results,the optimum selection is made among the aforementioned excavation schemes.The conclusions can be drawn that center-diaphragm method is best in controlling deformation and stress of surrounding rock;ring-opening and core-retaining excavation method is the most applicable to deep-buried weak rock;the heave of the invert should be regarded as one of the major criterion for surrounding rock stability under high geo-stress and large deformation;the effect of vertical stress on supporting structure is more obvious than the effect of the horizontal stress when excavating in the deep-buried tunnel.