Study on deformation law of leveling and uplift of shallow clay layer and surface water-saturated sand layer

The shallow water-saturated sand layer affected by mining has mobile fluidity. In order to study the impact on the deformation of the overlying clay layer, a special physical simulation test system was used to study the impact of the coal seam on the shallow water-saturated sand layer with high water level. On the basis of on-site simulation, the shape and stress change process of the overlying clay layer under the condition of water injection and pressurization were simulated by FLUENT, and the abnormal deformation mechanism of surface movement was analyzed. The research results show that the movement and deformation of the clay layer are the result of the combined action of gravity and seepage, and the natural repose angle cannot be taken as the dominant factor of the leveling and uplift of the clay layer; under the action of hydrostatic pressure, the sand layer reaches the critical hydraulic gradient, which makes the sand layer activate and flow, and the flow velocity difference between the flowing sand layer and the clay layer occurs, resulting in the abnormal expansion of the subsidence area; in the process of changing the thickness of the clay layer from thin to thick, the main object affecting the overall uplift height changes from sand layer to clay layer, and the angle has little effect on the uplift height of sand layer when the clay layer thickness is larger. The angle of sand layer is positively correlated with the uplift length and offset distance of clay layer, and the deformation rate gradually increases with the increase of angle. The thickness of clay layer is positively correlated with leveling distance and negatively correlated with the uplift length, and the smaller the thickness, the more likely it is to be deformed and destroyed by movement. The influence of angle is relatively large, the continuous increase of the dip angle of the sand layer is the main reason for the increase of the interlayer dislocation, the increase of the horizontal movement and the expansion of the influence range of the surface subsidence.