水沙混合物非Darcy裂隙渗流试验研究

西部煤田因埋藏浅、厚度大,常采取大采高、快速推进的方式开采,开采时,覆岩破坏易形成贯通裂隙,当煤层上方存在水源和厚沙层时,易引发采场突水溃沙事故。裂隙中水沙混合物的渗流规律及失稳条件是探究突水溃沙的关键问题,以径向裂隙岩样和不同粒径、不同质量浓度的水沙混合物为研究对象,设计一套裂隙水沙混合物渗流试验系统;通过改变沙的质量浓度和粒径大小进行裂隙水沙混合物渗透特性测试,得到水沙混合物裂隙渗流特性参数(有效流度I_e和非Darcy流因子β)。试验结果表明:当沙粒径小于0.180 mm、质量浓度小于80 kg/m~3时,水沙混合物可以视为幂律型流体;随着沙质量浓度和粒径增大,稠度系数增大,幂指数随之减小。水沙混合物在裂隙中渗流速度-压力梯度可用二项式关系式拟合。有效流度I_e、非Darcy流因子β与水沙混合物的质量浓度ρs分别呈幂指数函数关系,随质量浓度增大有效流度I_e也随之增大,非Darcy流因子β则随之减小。水沙混合物在裂隙岩石渗流时,沙质量浓度和粒径对渗流参数都产生影响,但沙密度是主要影响因素。

Experimental study on non-Darcy seepage of water and sediment in fractured rock

Due to the excavation of coal seam with shallow depth,large seam thickness,thin bedrock and thick sand layer,the failure of overburden strata can usually induce the connected crack. Owing to the movement of surface water or groundwater,the sand layer flows to mine goaf through the fractured rock,which often leads to the disaster of water inrush and sand collapse. In order to study the permeability law of water and sand flows in the fractured rock,the set test system of water-sand seepage in fractured rock was designed. The result shows that the mixture of water and sand can be regarded as power-law fluid as particle size is less than 0.180 mm and the concentration of sand is less than 80 kg/ m³. Along with the enlargement of particle size of sand and mass concentration,the consistency coefficient becomes greater. The relationship between velocity and pressure gradient can be described by binomial relation. Effective fluidity Ie mass concentration ρs and non-Darcy β-mass concentration ρs belong to power-exponent function,which means the increase of mass concentration will result in the increase of effective fluidity Ie and the decrease of non-Darcy factor β. Mass concentration of sand has more influence on the permeability parameters compared to the particle size of sand.