Stability criterion of overburden structure above goaf under building load and its application

The rational utilization of coal mine subsidence areas is one of the main ways to solve the contradiction between the scarcity of construction land and rapid urbanization.The sudden instability of mining overburden in the subsidence area will lead to the destruction of new buildings in the coal mine subsidence area.In this paper, the stability of mining overburden under a load of new buildings is studied by means of theoretical analysis, numerical simulation, and field measurement.Aiming at the stability of mining overburden under load, the structural characteristics of mining overburden and the characteristics of additional stress distribution in rock mass caused by the surface load are analyzed using theoretical analysis.Based on this, the mechanical model of mining overburden stability under load is established.The mechanical conditions of the model are analyzed, and combined with the instability conditions of masonry beam, it is obtained that the criterion of whether the mining overburden slides and loses stability with the increase of load under surface load.When the rotation angle and fragmentation of articulated rock blocks meet i< 0.5sin θ₁ or i> sin θ₁, the possibility of instability of mining overburden structure will gradually increase with the increase of surface load.The rotation angle and fragmentation of articulated rock blocks comply with 0.5sin θ₁< i< sin θ₁, the mining overburden will not rotate with the increase of load.On the basis of theoretical analysis, the established mechanical model is applied to the actual project.According to the general situation of the new project in the subsidence area of the longwall mining with top coal caving, the stability of the mining overburden structure under the action of the proposed building is analyzed and evaluated using the method of numerical simulation and theoretical analysis in the early stage of building construction.Thus, the safety of the proposed project is determined.After the completion of the building, the surface deformation of the new building is monitored by PSInSAR technology.It is found that there is no sudden deformation of the surface in one year since the building is completed, which verifies the safety of the project and the rationality of the mechanical model of mining overburden structure under the load.