降雨-滑坡-隧道系统灾害演进机制研究——以重庆奉溪高速公路杨家湾隧道为例

Disaster Evolution Mechanism of Rainfall-Landslide-Tunnel System:a Case Study of Yangjiawan Tunnel of Fengxi Highway in Chongqing,China

为研究降雨条件下隧道-滑坡体系的灾变演化过程以及隧道受力响应特征,以重庆奉溪高速公路杨家湾隧道为例,通过室内模型试验,对降雨条件下隧道-滑坡体系灾害演进机制进行研究。结果表明:1)在降雨入渗作用下,坡体灾变演化过程为坡顶张拉—坡中蠕动滑移—坡脚牵引破坏;2)受地下水软化作用,土体发生蠕动变形,多余下滑力沿滑带方向向下传递,在坡脚形成较大的压应力并作用于隧道山侧;3)隧道拱顶、山侧拱腰和拱脚,特别是拱顶极易产生较大的应力集中,导致隧道拱顶产生竖向张拉裂缝;4)整个隧道模型在降雨作用下以受压力为主,越靠近隧道进口段,隧道受偏压作用越明显,山侧与河侧弯矩值相差5.1~5.5倍,两侧受力不均,形成典型偏压隧道。

This case study aims to investigate the disaster evolution process of tunnel-landslide system and tunnel stress response characteristics under rainfall condition and reveal the evolution mechanism of the rainfall-landslide-tunnel system.This study is conducted on tunnel landslide of Yangjiawan tunnel of Fengxi highway in Chongqing,China.The laboratory model test used in this study reveals the following results.(1)Under rainfall infiltration,the slope disaster evolution process shows a slope top tensioning-middle slope creeping slip-slope foot traction damage trend.(2)As the soil is softened by groundwater,it creeps and deforms,resulting in the downward transmission of the excess sliding force along the direction of the slip zone.This results in the formation of a large compressive stress at the slope foot that acts on the mountain side of the tunnel.(3)The tunnel crown,arch waist,and foot of the mountain side are prone to large stress concentrations,resulting in vertical tension cracks in the tunnel crown.(4)The whole tunnel model is mainly subjected to pressure under rainfall,and when entrance section is closer to the tunnel,the tunnel is subjected to bias pressure.The difference in bending moment values between the mountain side and the river side is 5.1~5.5 times,with uneven forces on both sides that forms a typical bias tunnel.