断层破碎带隧道围岩稳定性的离散元模拟研究

断层破碎带是隧道施工中常见的不良地质体之一,容易导致隧道围岩失稳甚至塌方等问题。为了分析其对隧道围岩稳定性的影响规律,依托港珠澳大桥连接线南湾隧道,利用离散元软件PFC~(2D)建立二维分析模型。结果表明:断层破碎带作用下隧道围岩应力呈非对称性,当断层位于受拉一侧时,断层对隧道水平位移的影响更为明显;当断层穿越隧道轮廓面时,断层对隧道围岩竖直方向位移的影响比水平方向位移更加显著;对比断层比邻与穿越隧道两种情况,断层与隧道相交时的最大潜在松动破坏区是未相交时的2倍以上;现场监测结果表明,当断层与隧道边墙位置相交时,该断面的位移最大且相比其他断面位移值明显增大,约为其他断面相同位置位移的2.5倍,这与数值计算中断层破碎带对潜在松动破坏区的影响规律类似。

Study on Discrete Element Simulation of Tunnel Surrounding Rock Stability with Fault Fracture Zone

The fault fracture zone is one of the common unfavorable geological bodies in tunnel construction, which may easily lead to instability or even collapse of tunnel surrounding rock. In order to analyze its influence on the stability of tunnel surrounding rock, the Nan-wan tunnel along the connecting line of Hong Kong-Zhuhai-Macao bridge is taked as the background by this paper, and established a two-dimensional analysis model by using the discrete element software PFC2D. Combined with the construction monitoring measurement results, the following conclusions were drawn:(1) The stress of the surrounding rock of the tunnel under the fault fracture zone is asymmetric. When the fault is located on the tension side, the effect of the fault on the horizontal displacement of the tunnel is more pronounced. (2) When the fault crosses the contour plane of the tunnel, the influence of the fault on the vertical displacement of the surrounding rock of the tunnel is more significant than that in the horizontal direction. (3) Comparing faults to neighboring and crossing tunnels, the maximum potential loosening damage zone when the fault intersects the tunnel is more than twice the maximum collapsed area when the fault is not intersected. (4) The on-site monitoring results show that when the fault intersects the position of the tunnel side wall, the displacement of the section is the largest and the displacement value of the section is significantly increased, which is almost 2.5 times of the displacement of the same position of other sections. This is similar to the numerical calculation of the effect of the disruption zone breaking zone on the potential loose zone.