近距离煤层开采风化岩体载荷传递效应及失稳特征研究

Study on load transfer effect and instability character of weathered rock mass under close distance coal seams mining

以库拜煤田近距离煤层开采突水工作面为例,通过岩石力学声发射测试,获得了风化岩石加载变形破坏过程中裂隙扩展演化和声发射特征。建立力学模型分析了近距离煤层开采岩体破断特征及风化岩体的载荷传递效应,并通过数值模拟验证了风化岩体对下部岩层破坏的影响。采用三轴加卸载声发射实验模拟研究重复采动条件下岩石裂隙扩展演化特征,并结合现场观测统计分析了采动裂隙发育特征及风化岩体对采动裂隙发育规律的影响。基于三轴渗流特性测试,研究了水压作用下风化岩石裂隙渗流规律。研究结果表明:风化岩石声发射特征累计统计值呈连续光滑增大,但声发射能量、事件均较弱,受埋深浅、围岩应力小的影响,采动易引起裂隙扩展形成导水通道。风化带使上部岩体载荷传递增大,促进下部岩层的损伤及主关键层的破坏,近距离煤层开采顶板硬岩发生复合破断后,应力-渗流耦合作用岩体裂隙进一步扩展,产生发育的地表地裂缝。近距离煤层开采岩体发生重复扰动破坏,采动裂隙产生叠加破坏,风化带成为上下部裂隙的连接纽带,使导水裂隙带高度增大。风化岩石原始渗透率较大,发生塑性变形至裂隙贯通破坏后渗透率增大2~3倍,水压作用促进风化岩石裂隙扩展,发生强度劣化效应,成为良好的导水通道,导致松散层水和地表水涌入工作面,发生突水事故。

Weathered rock fissures extend evolution and acoustic emission signature were obtain from a rock mechanics acoustic emission test on the water burst catastrophe of nearby coal seams in the KuqaBaicheng coalfield.Fracture characteristics and load transfer effect of weathered rock were analyzed under close coal seams mining through mechanical model,and the effect of weathered rock on the lower strata destruction was verified through numerical simulation.Simulation study on the evolution of rock fissures under repeated mining was conducted through triaxial loading and unloading acoustic emission test.Under the statistical framework of field observation,the mining fracture development characteristic and the impact of weathered rock were analyzed.Based on triaxial seepage characteristics test,fissure seepage rule of weathered rock was researched.The research results showed that the acoustic emissions test parameters of weathered rock increased continuously and gradually while the unweathered rock showed stepwise wave increments and high emitted energy.Fissures spread easily and became water-conducting channels because of the shallow buried depth and low surrounding rock stress.Weathered rock promoted lower strata damage and key stratum destruction while increasing load transfer.When compound breakage occurred in the roof's hard strata with near proximity coal seam mining,further extension developed for rock fractures under stress-seepage coupling and produced enormous fractures on the earth's surface.The roof stratum under long-distance coal seam mining repeated disturbance failures,which caused mining cracks to superimpose on one another.Weathered rock served as the link between upper and lower fractures and caused the height of the fissure zone to rise.Weathered rock had a relatively high permeability that increased by two or three times after destruction.Under water pressure,worn rock showed signs of fracture extension and strength degradation,which created a water-inducing channel and thereby outburst of unconsolidated strata and surface water.Water burst disaster was inevitable thereafter.