软岩引水隧洞施工开挖过程围岩变形规律研究

摘要

A diversion tunnel with soft rockmass in the central region of Yunnan Province is modeled and the three dimensional explicit finite difference program FLAC3D is used for the simulation of construction and excavation process. The calculations show that, ( a) the space constraint effect of excavation face is existed in soft rock tunnel, the surrounding rock stress is slowly released and the displacement is also gradually increased; (b) on the cross section, the influence scope of space effect is about 3D on vault deposition displacement, and about 1.5D on horizontal displacement of haunch and uplift displacement of arch bottom; (c) the space effect will gradually disappear in the process of tunnel face advance, the displacement of vault and arch bottom will be stable behind excavation face about 2.5D~3D and the displacement of haunch is about 2D, then the deformation of surrounding rock will gradually be convergence; and ( d) the primary support in soft rock tunnel should be applied in time, which can improve the self-bearing capacity of surrounding rock to limit the growth of displacement.%以云南省滇中引水工程某段软岩引水隧洞建立实体模型，应用三维显式有限差分法程序FLAC3D对其施工开挖过程进行三维数值模拟。计算结果表明，软岩隧洞受到开挖面的空间约束效应，围岩应力逐步释放，相应围岩位移也逐渐增加；在横断面上，拱顶围岩沉降位移沿竖直径向的空间效应主要影响范围在3倍洞径（3D）左右，而拱腰围岩水平位移和拱底隆起位移在1.5D左右；掌子面向前推进过程中，掌子面的空间效应逐渐消失，拱顶、拱底位移在施工开挖面后方约2.5D~3D处趋于稳定，拱腰位移在约2D左右趋于稳定，围岩变形收敛；软岩隧洞需要及时施作初期支护，以提高围岩自承能力，限制位移的增长速度。