西部矿区突水溃沙类型及机理研究
Types and mechanism of water-sand inrush disaster in west coal mine
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摘要: 突水溃沙灾害是西部浅埋煤层开采常见问题之一,对矿井安全生产和当地脆弱的生态环境都有着极其不利的影响。在分析西部矿区突水溃沙主要类型的基础上,通过自主研制多孔介质水沙两相渗流试验系统,从多孔介质孔隙度、破碎岩石粒径、沙粒粒径3个方面对突水溃沙的机理进行了研究。结果表明:西部矿区突水溃沙主要类型可以分为切落裂缝型、冒落型、钻孔诱发型3类;孔隙度对发生突水溃沙灾害的影响与破碎岩石粒径有着密切关系,随着破碎岩石粒径增大,孔隙度改变对压力梯度和沙粒流失量的影响程度将降低。沙粒流失量随孔隙度的降低而减少,低孔隙度含水层发生溃沙的可能性将大大降低;同一孔隙度和沙粒粒径条件下,含水层砾石颗粒越小,发生突水溃沙灾害所需的压力梯度就越大,沙粒流失量也越小,越不容易发生突水溃沙灾害;同一孔隙度条件下,0.074~0.25 mm的细砂较之0.25~0.83 mm的中砂或者粗沙更易发生突水溃沙灾害,其所需的启动压力也较小,随着破碎岩石粒径增大,其沙粒流失量呈非线性显著增加。Abstract: Water-sand inrush disaster is one of the most common problems in the shallow buried coal seam mining in western China region,and has adverse effect on mine safe production and fragile ecological environment. After analy- zing the types of water-sand inrush disaster in western coal mines,the influence mechanisms of porosity of porous me- dium,the particle sizes of broken rock mass and sand on water-sand inrush disaster are studied using self-developed porous medium two-phase water-sand flow testing system. The results show that water-sand inrush disaster can be di- vided into three types:cutting type,caving type and drilling induced type. The effect of porosity on water-sand inrush disaster has a close relation to the particle sizes of broken rock mass. The influence of porosity on pressure gradient and sand loss amount decreases with the particle sizes increase of broken rock mass. The sand loss amount increases with the increasing porosity and the possibility of water-sand inrush in low-porosity aquifer is less. At the same porosity and particle sizes of sand conditions,the smaller the particle sizes of gravels in aquifer,the higher the required pres- sure gradient for water-sand inrush disaster is,and the smaller the sand loss amount is. At the same porosity condition, the sand with 0. 074 -0. 25 mm diameter causes water-sand inrush disaster more easily than the sand with 0. 25-0. 83 mm diameter,and the smaller the particle sizes of sand is,the smaller the starting pressure of water-sand inrush disaster. At the same porosity condition,the sand loss amount increases nonlinearly with the particle sizes increase of broken rock mass.