隧道开挖对下伏水平薄煤层采空区地层的扰动及衬砌受荷特征

为探明下伏薄煤层采空区地层中隧道施工对地层的扰动以及衬砌结构受荷特性，采用离散元颗粒流软件，从细观角度对隧道开挖引起的地层应力变化特性进行了模拟分析，同时在室内开展模型试验量测了下伏煤层采空区地层隧道衬砌背后土压力以及二次衬砌结构内力（轴力、弯矩），分析了特定围压下间距对土压力和二次衬砌受力的影响。结果表明，下伏煤层采空区地层因隧道开挖引起的围岩松动区呈“O”形分布，隧道下伏围岩颗粒接触力反而小于隧道上覆围岩；洞周允许位移越大，颗粒接触力链间断区域越大；间距越小，颗粒接触力链间断区域越大，当间距大于2.0D（D为隧道跨度）时，下伏采空区对隧道围岩颗粒接触力影响逐渐消失，降低了地基反力，间距越小，降低程度越高；二次衬砌内力分布有一定的离散性，二次衬砌裂缝最先出现在拱底，是隧道主体结构的薄弱环节。

Soil disturbance caused by tunnel excavation and lining loading characteristics in underlying horizontal thin coal mined-out area

In order to study ground disturbance induced by tunnel construction and characteristics of lining structure under load in underlying horizontal thin coal mined-out area, numerical analysis software is used to simulate the vibration of ground stress from meso-level; meanwhile, indoor tests of similarity model is carried out to measure earth pressure acting on tunnel lining and structure internal force of secondary lining(axial force and bending moment) in the strata beneath thin seam mined-out area to analyze the influences of pitch on the earth pressure and internal forces of secondary lining under confining pressure. The test results demonstrate that the loosening zone of surrounding rock induced by tunnel excavation takes on O-shape in underlying horizontal thin coal mined-out area; and the particle contact force of the underlying wall rocks of the tunnel is less than that of the overlaying rock of the tunnel. The greater the convergence of tunnel inner perimeter, the greater the particle contact force of discontinuity region. The smaller the pitch, the larger the particle contact force discontinuity region, when the pitch is larger than 2.0D, the impact of underlying mined-out area to particle contact force fade away. The subgrade reaction is reduced by underlying mined-out area; the smaller the pitch, the higher the degree of reduction. Internal force of secondary lining is discrete distributed. As the weak part of main structure of tunnel, the first crack appeared in invert of secondary lining.