| Taking the tunnel of a high-speed railway as the engineering background,and based on the engineering geological exploration data,this paper uses PFC2D particle flow discrete element numerical software to simulate the rock mass failure process of coal mine goaf,and comprehensively determines the height growth of three zones of goaf according to theoretical calculation,engineering geological analogy,numerical simulation analysis and on-site drilling verification.A three-dimensional numerical model is established by using Flac3D finite difference software,focusing on the analysis of surface subsidence,surrounding rock deformation,overlying rock movement parameters of goaf and surrounding rock stability of tunnel during the construction of deep tunnel which passes through the complex goaf.At the same time,seismic load and train load time history curves are established by Midas-GTS to analyze the influence of residual deformation of coal mine goaf on tunnel stability.The research results can provide some value for similar practical projects.The main achievements of this paper are as follows:(1)In this paper,the height of caving zone and water diversion fracture zone are obtained based on theoretical calculation,and then the rock mass failure process of coal mine goaf is simulated by PFC2D particle flow discrete element numerical software.The height growth of the three zones of goaf is determined comprehensively according to the methods of engineering geological analogy,numerical simulation analysis and field drilling verification,which provides a basis for the verification of the simulation idea of coal seam mining caving in this paper.(2)In this paper,through the establishment of a three-dimensional numerical model,the case of a high-speed railway tunnel passing through coal mine goaf is analyzed and studied,and the influence of residual deformation of coal mine goaf on tunnel stability and overlying rock movement under static and dynamic load are obtained.The calculation results show that the residual deformation of the goaf of the selected three cross-sections is calculated numerically,and the results show that:?The maximum increment of lateral displacement caused by residual deformation of goaf is 17.16mm for tunnel vault,10.14mm for arch bottom,15.45mm for left wall,11.05mm for right wall,43.18mm for vertical direction displacement increment,31.64mm for arch bottom,29.59mm for left wall and 30.82mm for right wall.The residual deformation of the goaf has a certain influence on the stability of the tunnel,which is not conducive to the long-term stability of the tunnel.?Under the earthquake load,the tensile stress at the top of the tunnel under the coal mine goaf increases,the tensile stress at the bottom of the tunnel decreases,the compressive stress of the left wall increases and the compressive stress of the right wall decreases,which will aggravate the unfavorable stress form of the tunnel,but the stress increment is small.it has little influence on the stability of tunnel surrounding rock.?Under the action of train vibration load,the normal tensile stress at the top and bottom of the tunnel,the normal compressive stress on the side wall,and the train vibration will aggravate the unfavorable stress form of the tunnel.The minimum value of radial stress increment of tunnel under train dead weight is 15Pa and the maximum value is 192 KPa.The influence of surrounding rock deformation,stress,velocity and acceleration caused by train vibration load is relatively small.(3)Fully considering the complexity of internal deformation of rock strata caused by mining,the joint action of underground mining and surface slope effect,the influence of repeated mining of multiple coal seams,the deformation sensitivity of high-speed railway engineering and other unfavorable factors,from the point of view of safety,the strike boundary angle ?0 of goaf is 48°,and the influence mileage of coal mining on tunnel stability is 155m length. |
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