Longwall extraction of coal seam disturbs the whole overburden strata, from the coal seam to the surface, and forms a subsidence basin. This paper investigated the mechanism of the overburden strata bending deformation, the alluvium mechanical parameters, and their effect on surface subsidence by the theoretical analysis and numerical simulation analysis. The dynamic processes of overburden failure and surface subsidence due to longwall mining was analyzed by a novel two-dimensional trapezoidal-area method. A “π-shaped” model was first developed to reveal that surface subsidence consists of the overburden strata bending deformation and the subsidence of the alluvium. The process and mechanism of the overburden strata bending transfer were analyzed, and two mechanical models of the strata bending deformation were established, i.e., the strata suspended bending model and the strata overhanging bending model. The maximum subsidence equation of the overburden strata bending basin was derived based on the theoretical analysis. Also, the effect of the alluvium mechanical parameters on the surface subsidence was investigated by numerical simulation analysis. The rationalities of the numerical simulation were validated by the field measurements. The results show that surface subsidence increases logarithmically during increased alluvium thickness and decreases exponentially and logarithmically during increased internal friction angles and increased cohesions, respectively.

煤层的长壁开采扰动了整个覆盖层，从煤层到地表，并形成了一个沉陷盆地。通过理论分析和数值模拟分析，研究了上覆地层弯曲变形的机理，冲积层力学参数及其对地表沉陷的影响。采用新型的二维梯形区域法分析了长壁开采引起的上覆破坏和地表沉陷的动力学过程。首先建立了一个“π形”模型，以揭示地表沉陷由上覆地层弯曲变形和冲积层的沉陷组成。分析了覆盖层地层弯曲传递的过程和机理，建立了地层弯曲变形的两个力学模型，即：地层悬挂弯曲模型和地层悬垂弯曲模型。在理论分析的基础上，推导了上覆地层弯曲盆地的最大沉降方程。此外，通过数值模拟分析研究了冲积层力学参数对表面沉降的影响。通过现场测量验证了数值模拟的合理性。结果表明，在增加冲积层厚度的过程中，表面沉降分别呈对数增加，而随着内部摩擦角的增加和内聚力的增加，表面沉降分别呈指数和对数减小。通过数值模拟分析研究了冲积层力学参数对地表沉陷的影响。通过现场测量验证了数值模拟的合理性。结果表明，在冲积层厚度增加时，地面沉降量呈对数增加趋势，在内部摩擦角增加和内聚力增加时，地面沉降分别呈指数和对数减少趋势。通过数值模拟分析研究了冲积层力学参数对地表沉陷的影响。通过现场测量验证了数值模拟的合理性。结果表明，在冲积层厚度增加时，地面沉降量呈对数增加趋势，在内部摩擦角增加和内聚力增加时，地面沉降分别呈指数和对数减少趋势。