地下水位下降对采矿覆岩下沉影响探析

地下采煤会导致地表下沉盆地的形成。然而地下水尤其是承压水的流失即水位降低对地表下沉盆地的形成存在不可忽视的影响，而对两者之间的关系及其过程的力学机理是岩移领域亟待研究的课题之一。矿区地下水位降低的主要原因为承压水通过采动裂隙向下渗流、煤层开采前顶板岩溶含水岩层的疏干以及地面人为钻井取水。根据对一具体矿区地下水位下降对地表沉陷影响实测数据的分析得出，在以采煤为主导条件导致地表下沉的过程中，几乎全部的开采沉陷量中均包含有由于含水层释水而造成的沉陷量。通过对上覆岩层力学机理分析，指出水位降低对覆岩移动、地表下沉的影响是由于一定地质条件下可渗水性岩石的物理力学特性、渗水对其它岩石的软化、释水后原冲积层的压密固结以及水渗透过程中的水岩耦合作用等因素综合作用所致。同时，在以上理论的基础上还探讨性地建立了地下水位下降对地表下沉贡献模型，在此模型基础上可以建立2个或2个以上影响因素对地表下沉的贡献模型。最后以框图形式概括了地下水位下降及其对地表下沉影响的综合过程。

Study on the influence of ground-water lowering to the subsidence of overlying strata in mining area

The surface subsidence basin is the result of underground coal mining. However, the underground water lowering, which takes place in the water bearing layer in chief, has the inevitable influence on the surface subsidence. The relationship between them is one of the most important problems which are studied in the domain of mining strata subsidence. This paper produces that the occasions of the underground water lowering have three aspects in the relationship between the water lowering and the surface subsidence. The first is that a great deal of water in water bearing layer flows into the rock layers which have crevices and absorbing water through the crack. The second is the water dredging in water bearing layer before the new coal mining begins to work. The third is the bore-hole made by local residents through which the underground water is extracted. Through studying the data of the influence on surface subsidence resulted by ground water lowering in a coal mining area, during the rock strata being damaged by mining, it has the result that almost all mining subsidences have the influence led by the lowering ground water. On the basis of mechanical analysing the property of the overlying strata, the paper points out that the surface subsidence is affected by the ground water lowering by the way of the physic-mechanical properties of permeable rocks in mining area, of the softening action on some kinds of water absorbing rock by the pervading water, of the condense in thick allurial and of the rock and water soil-fluid coupling effect during the water osmosing. The surface subsidence contribution model composed of the actions of the subsidence and the lowering of ground water is established on the basis of what discussed above. According to this model, it can give the surface subsidence contribution model composed of more than two actions. And at last, the paper gives the figure of the reason of the underground water lowering and of the process which illustrates how the water lowering act on the rock strata subsidence.