Abstract: 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.

Key words: tunnel excavation, underlying mined-out area, PFC, soil disturbance, model test, loading characteristics