超深层黄土滑坡作用下既有隧道结构体系力学特征

黄土地区滑坡灾害频发，滑坡尤其是超深层滑坡对既有隧道结构受力变形有重要影响，隧道滑坡体系变形特性、力学响应一直是学术界和工程界关注的焦点. 以某超深层滑坡地质灾害中的铁路隧道工程为依托，建立了“超深层黄土边坡-滑带-隧道”FLAC3D三维数值模型；利用基于位移突变的局部强度折减法模拟坡体失稳临界状态；针对不同滑带隧道相对位置，揭示了滑坡诱发条件下既有隧道衬砌结构受力及变形特征变化规律，并结合现场实测数据及结构破损情况初步分析了依托工程事故原因. 数值模拟结果显示:当滑带在隧道上方时，受中间围岩“牵动”作用明显，墙脚水平位移最大值27.83 mm；当滑带在隧道下方时，隧道“坐船”作用显著，墙脚水平位移最大值185.61 mm；当隧道位于滑面上方时危险性更高. 实测结果显示:沿纵向隧道位移呈“坐船”状，墙脚水平位移最大值为105.35 mm，小于滑带在隧道下方时工况；依托工程为黄土（粉土）-基岩滑坡，隧道位于滑体内，且滑坡仍处于蠕动状态，还未达到滑动临界状态. 

Mechanical Characteristics of Existing Tunnel Structure Affected by Super Deep Loess Landslide

Landslide disasters occur frequently in loess area. Landslides, especially super deep landslides, have a significant impact on the stress and deformation of existing tunnel structures. The deformation characteristics and mechanical responses of tunnel-landslide systems are extremely complex and have been the focus of academic and engineering researchers. Based on a railway tunnel project in a super deep landslide geological disaster, a three-dimensional numerical model of the "super deep loess slope-sliding zone-tunnel" system was established using FLAC3D. The local strength reduction method based on displacement mutation was used to simulate the critical state of slope instability, and variation laws of the mechanical and deformation characteristics of the existing lining structure induced by landslide were analyzed for cases of different relative positions between sliding zones and tunnels. In addition, combined with field measurements and structural damage conditions, the causes of engineering accidents were preliminarily analyzed. Numerical simulations indicate that when the sliding zone is above the tunnel, the surrounding rock exerts a significant pulling effect on the tunnel, and the maximum horizontal displacement of 27.83 mm occurs at the wall foot; when the sliding zone is below the tunnel, the tunnel structure has an obvious overall lateral translation, resulting in a maximum horizontal displacement of 185.61 mm at the wall foot. The most dangerous case is when the tunnel is above the sliding surface. The field measurements indicate that the tunnel has an overall lateral translation perpendicular to the longitudinal axis. The maximum translation (105.35 mm) at the wall foot is smaller than the case when the sliding zone locates below the tunnel. Results also show that the selected tunnel project was built in a loess (silt)-bedrock landslide, which is still in a creeping state and has not yet reached the sliding critical state.