某隧道进口段边坡的变形破坏机理分析

某隧道进口段滑坡的发生是由于隧道开挖过程中破碎围岩向隧道开挖临空面位移,进而引发的坡面岩土体的失稳。数值模拟结果表明,因隧道开挖引起的洞顶区边坡岩体应力水平下降的区域一直延续到地表,这种应力场的变化会直接导致边坡表面的变形和破坏,表现在以隧道轴线为中心,向两侧呈扇形展开的坡体产生了一定的沉降变形。对比结果表明滑坡区与由隧道开挖引起的坡体附加位移较大的区域基本相当,说明此滑坡是由于隧道开挖引起了围岩应力场调整,导致围岩产生向洞内的位移变形,从而使岩体发生松动而引发的。

MECHANISM ANALYSIS OF THE LANDSLIDE HAZARD AT A TUNNEL ENTRANCE

The landslide at a tunnel entrance is triggered by the collapse of the slope soil and rock that induced by the displacement of the fractured surrounding rock towards the excavating surface of the tunnel. Numerical simulation indicates that the stress reducing area above the tunnel roof extends to the terrene. The change of stress field directly results in the deformation of the slope surface that exhibits as settlement of the slope in fan shape along the tunnel axis. Numerical simulation also indicates that the landslide area coincides with the area in which the additional displacement is comparatively larger due to the excavation of the tunnel, and it can be concluded that the landslide is caused by the loosing of the rock mass because of the displacement of the fractured adjacent rock towards the excavating surface of the tunnel due to the stress redistribution of the adjacent rock of the excavated tunnel.