引水隧洞穿越大型断裂带围岩力学响应

针对引水隧洞地质条件复杂、岩性差异大的特征,建立仿真三维模型,采用Mohr-Coulomb弹塑性本构模型,以分段开挖方式,对比纯开挖、支护开挖围岩径向位移、应力响应差异,分析研究隧洞穿越大型断裂带过程中的围岩力学行为。结果表明,断裂带右侧初始自重应力明显偏低,附近石灰岩段存在应力集中现象,开挖后断裂带左侧洞顶径向位移明显大于右侧;纯开挖时,已开挖部分洞壁径向应力趋于零,掌子面前方约3倍洞径范围应力释放与应力集中现象突出,各分段掌子面附近出现径向位移极小值点;开挖支护时,已开挖部分洞壁径向应力维持在较高水平,处于三向压缩状态,掌子面前方应力集中现象减弱,在各分段开挖掌子面前方应力释放区内,径向应力极小值点和径向位移极大值点一一对应,间接反映支护时机对围岩力学响应的影响。研究成果可为引水隧洞施工提供指导。

Mechanical Response of Surrounding Rock in Diversion Tunnel Passing Through Large Fault Zone

Three-dimensional simulation model of diversion tunnel was established considering the characteristics of complex geological conditions and large difference in lithology. Based on the Mohr-Coulomb elastic plastic constitutive model and stage-excavation, mechanical behaviors of surrounding rock in the process of tunnel passing through large fault zone was analyzed by contrasting the differences of radial displacement and stress response between un-supporting excavation and supporting excavation. The results show that the initial geostatic stress is obviously low, and the stress concentration exists in the limestone section on the right side of the fault zone. The radial displacement on the left roof of the fault zone is significantly larger than the right after the excavation. While un-supporting, the wall radial stress of the excavated part tends to zero, and the stress release and the stress concentration phenomenon are obvious in front of the tunnel face about 3 times of the diameter, the local minimum of radial displacement appears near the tunnel face of different stages. While supporting, the wall radial stress of the excavated part maintains at a higher level in the state of three-dimensional compression, and the stress concentration phenomenon is weakened in front of the tunnel face. There is a one-to-one correspondence between radial stress minimum point and radial displacement maximum point in each stress release area of the front of different stage of the tunnel face, which indirectly reflects the influence of supporting time on the mechanical response of surrounding rock. Research results can provide guidance for the diversion tunnel construction.