采空区不同岩性破碎岩石压实变形及声发射特征研究

Compaction deformation and acoustic emission characteristics of fractured rock with different lithology in goaf

采空区不同岩性冒落破碎矸石的压实特性及承载力学性质对上覆岩层移动破坏有重要影响。采用侧限压缩试验与声发射测试试验方法,对相同级配的砂岩、砂质泥岩两种单一岩性及砂岩-砂质泥岩组合岩性破碎岩石在侧限压缩条件下的变形特征、破碎特征及不同压缩阶段的声发射特征进行了研究。结果表明:在加载前期,破碎岩石的应变随时间的变化曲线存在直线上升段,随时间增加,呈现急剧上升后趋于平缓的特征;不同单一及组合岩性破碎岩石在侧限受压过程中应力与应变均呈非线性关系;根据破碎岩石的应力-应变特征将破碎岩石的压缩变形过程划分为快速压密阶段、缓慢压实阶段及稳定压固阶段。随着轴向压力逐渐增大,破碎岩样的大颗粒骨架破坏、中等颗粒移位滑动、小颗粒填充孔隙;不同岩性的应变与应力呈正相关关系,孔隙率与应力呈负相关关系,组合岩性岩样介于单一岩性岩样之间;不同单一、组合岩性比例与破碎岩样分形维数呈指数函数关系;基于压实变形声发射测试试验结果将破碎岩石压缩过程划分为滑移流动变形阶段、压裂变形填充阶段及压密弹性变形3个阶段;不同阶段破碎岩样的累计计数及累计能量曲线均表现出阶段性的变化特征,随着应力增加,前期声发射累计振铃计数及累计能量表现出先快速线性增加,后趋于平缓,再上升的趋势,后期增加速率逐渐减小,曲线逐渐趋于平缓;组合岩性岩样的声发射累计计数及能量均介于单一岩性岩样之间。研究结果为采空区上覆岩层及地表移动、采空区安全治理提供有力的理论指导。

The compaction characteristics and mechanical properties of different lithologic broken gangues in the goaf significantly impact the movement and failure of the overlying strata.Confining compression and acoustic emission tests were conducted to study the deformation,fracture,and acoustic emission characteristics of sandstone and sandy mudstone with the same gradation(SSMSG),as well as the combined fractured sandstone and sandy mudstone(CFSSM),under confining compression conditions.The results indicated that,during the early loading stage,the strain curve of the broken rock initially exhibited a linear increase.As time progressed,it sharply increased before transitioning to a gentler incline.The stress-strain relationship of the SSMSG and the CFSSM was nonlinear under lateral compression.Based on the stress-strain characteristics,the compression deformation of the broken rock could be categorized into three stages:rapid compaction,slow compaction,and stable compaction.As the axial pressure increased,the broken rock samples experienced skeleton destruction of large particles,displacement and sliding of medium particle,and pore filling of small particles.The strain of different lithology showed a positive correlation with stress,while porosity exhibited a negative correlation with stress.The CFSSM fell between the behaviors of SSMSG.The fractal dimension of broken rock samples was exponentially related to the different proportions of the SSMSG and the CFSSM.Based on the acoustic emission test results,the compression process could be divided into three stages:sliding flow,fracturing filling,and compaction elastic deformation.The cumulative count and energy curves of broken rock samples at different stages exhibited characteristic periodic changes.With increasing stress,the cumulative AE count and energy showed a rapid linear increase in the early stage exhibit,followed by a slower increase before rising again.The acceleration rate decreased gradually in the later stage,resulting in a gentler curve.The cumulative AE count and energy in the CFSSM fell between those of the SSMSG.The research findings provide valuable theoretical guidance for managing the overlying strata,surface movement,and safety in the goaf.