巨厚松散层下煤层开采的抗渗透性破坏和煤柱安全性研究——以口孜东矿为例

采掘诱发裂隙导通顶板上覆含水砂层中产生的水力坡度是渗透型溃砂的关键判断依据之一，但是，到目前为止主要是采用定流量下的稳定流水力坡度表达式计算，而实际上，上覆含水层中水动力条件和涌水量在溃水溃砂过程中都是非稳定的。本文依据非稳定流理论，给出了二维潜水、承压水单井定降深模型下的水力坡度J的解析公式，并分析了J随时间和距离的演变特征。结果表明，对于潜水，J随与井的距离r的增加而下降，下降速度随r的增加而减小；存在拐点r′，当r<r′时，J随时间延长而下降，在r>r′时，J随时间延长而增加；随着地下水头H₀的增加，J是增加的；本文获得的潜水的非稳定流条件下的J大于潜水稳定流的J。对于承压水，J随r的增加而下降，下降速度随r的增加而减小；与潜水不同的是，在不同r处，J随时间延长而下降，不存在拐点；随着H₀的增加，J是增加的；本文获得的承压水的非稳定流条件下的J不总大于承压水稳定流的J。最后，在伊犁河谷某矿对本文方法进行了初步应用。

Internal Instability in soils: A critical review of the fundamentals and ramifications

The calculation of the actual hydraulic gradient in the overlying water-bearing sand layer of the roof aquifer during the mining process has always been one of the key bases in the judgment of roof sand inrush. However,so far,it has mainly used the expression of steady flow hydraulic gradient under constant rate. In fact,in the process of sand inrush,the hydrodynamic conditions and water inflow in the roof aquifer are unsteady. In this paper,based on the unsteady flow,we derived the analytical formula of hydraulic gradient J under the two-dimensional unconfined water and confined water single well fixed-drop model,and also analyzed the evolution characteristics of J with time and distance. The results show that for unconfined water,J decreases with the increase of r,and the rate of decline decreases with the increase of r. There is an inflection point r′,when r<r′,J decreases with time,when r>r′,J increases with time; with the increase of H₀,J increases. This paper obtained J under the unsteady flow of unconfined water is larger than that under the steady flow of unconfined water. For confined water,J decreases with the increase of r,and the decrease rate decreases with the increase of r. Different from unconfined water,at different r,J decreases with time,and there is no inflection point; with the increase of H₀,J increases. This paper obtained J under unsteady flow of confined water is not always larger than that under steady flow of confined water. Finally,this method was applied in the evaluation of water-sand mixture inrush assessment for a coal mine in the Yili River Valley,Xinjiang,China.