采动裂隙突水溃砂过程物理参量变化特征试验研究

Experimental studies on variation characteristics of physical parameters during water and sand burst through mining fractures

采动破断裂缝沟通上部浅埋松软岩层导致水砂混合物溃入井下,对矿井生产及相关工程设施的安全造成严重的影响,因此,研究浅埋松软岩层采动裂隙突水溃砂机制对认清突水溃砂灾害本质具有指导意义。首先,通过创建的裂隙内砂体突涌力学模型,分析了裂隙突水溃砂发生的极限平衡条件。其次,利用突水溃砂试验系统,借助流量传感器和孔隙水压传感器进行了不同初始水压条件下人工模拟裂隙内水砂溃涌试验,获得了流量、孔隙水压等参数变化特征,定量化分析了裂隙突水溃砂各阶段内水砂运移特征及各物理参量关联性变化特征。试验结果表明:裂隙内水砂溃涌全过程可以划分为4个阶段,即溃砂启动阶段、持续溃出阶段、淤积堵塞阶段和溃出平衡阶段。在第1阶段,流量瞬间增大,各监测点孔隙水压瞬间降低;在第2阶段,水砂逐渐充满通道内径,孔隙水压及流量基本保持不变;在第3阶段,通道内砂体发生部分淤积,造成流量逐渐降低,孔隙水压逐渐增大;在第4阶段可分为2种情况,一是当本阶段水压低于极限水压时突水溃砂停止,二是当高于极限水压时水砂突涌持续并稳定。一定初始压力下,发生运移的砂体具有一定的空间范围,距裂隙较远处孔隙水压的变化具有滞后性;随着初始压力的增大,裂隙通道砂体淤积堵塞所需时间降低,导致砂体持续溃出时间降低;初始水压达到阙值后,裂隙内水砂溃出体积率达到峰值且水压稳定。裂隙突水溃砂结束后,随着初始水压的增大砂体中部形成“塌陷坑”的空间分布范围存在增大的趋势。

Mining fractures coalesces with shallow buried cemented soft seam,which causes water and sand mixture burst into underground mine.It has a serious impact on the safety of mine production and related engineering facilities,so it is instructive to study the mechanism of water and sand burst caused by mining fractures in shallow buried cemented soft seam for understanding the essence of the disaster.Firstly,the limit equilibrium conditions of water and sand burst in fractures are analyzed through the mechanics model of sand body inrush in fractures.Secondly,by using the test system for water and sand burst,flow sensors and pore water pressure sensors,the simulation experiments of water and sand burst in fractures under different initial water pressures are carried out.The variation characteristics of flow rate,pore water pressure and other parameters are obtained,quantitative analysis is made on the characteristics of water and sand migration and correlation changes of physical parameters in different stages of water and sand burs.The test results show that the whole process of water and sand burst in fractures can be divided into 4 stages,namely,start-up stage,continuous outburst stage,silt blockage stage and outburst equilibrium stage.In the first stage,the flow rate increases instantaneously and the pore water pressure decreases instantaneously.In the second stage,water and sand gradually fill the channel,and the pore water pressure and water flow rate are basically stable.In the third stage,the sand body in the channel is partially silted,resulting in a gradual decrease in flow rate and an increase in pore water pressure.In the fourth stage,it can be divided into two situations:first,when the water pressure is lower than the limit water pressure,the water and sand burst stops;second,when the water pressure is higher than the limit water pressure,the water and sand continuous outburst and remains consistent.Within a certain range of initial pressure,sand body migration in a certain spatial range and the data change of pore water pressure far from the channel is lagging behind.With the increase of initial pressure,the time required for siltation and blockage decreases,which leads to the decrease of the duration of sand outburst.When the initial water pressure reaches a certain value,the volume ratio of water and sand outburst in the fracture reaches its peak value and the water pressure stability.After the test,with the increase of initial water pressure,the spatial distribution range of“collapse pit”in the middle of test chamber tends to increase.