充填体单轴压缩峰后应力—应变曲线特征及声发射参数研究

Study on Characteristics of Post-peak Stress-strain Curve and Acoustic Emission Parameters of Backfill under Uniaxial Compression

低强度充填体在充填法开采中控制地压时可能处于峰后破坏阶段,其峰后应力—应变曲线特征及声发射参数与地压控制关系密切。以程潮铁矿灰砂比为1∶6的全尾砂胶结充填体为研究对象,开展了充填体单轴压缩及声发射监测试验,得到充填体单轴压缩下的应力—应变曲线及声发射参数,采用能率和声发射事件对峰后应力—应变曲线特征及破坏过程进行了分析。结果表明:充填体峰后应力—应变曲线斜率为负值,先逐渐减小,后逐渐增大,最后基本保持不变,根据峰后应力—应变曲线斜率变化趋势可将其划分为AB段、BC段及C以后段,其中AB段应力—应变曲线逐渐变陡,斜率逐渐减小,呈上凸型,充填体表面宏观裂纹不断增多,强度劣化加速,能率先急剧减小后快速增大,声发射事件定位点局部比较集中;BC段应力—应变曲线变缓,斜率逐渐增大,呈上凹型,剪切裂纹扩展、汇合形成宏观剪切面,破坏过程变缓,能率较高且逐渐下降,声发射事件定位点聚集呈带状分布;C以后段应力—应变曲线斜率基本不变,剪切面出现滑移,充填体残余结构支撑外部荷载,能率和声发射事件大幅下降;充填体峰后声发射参数能较好地反映其应力—应变曲线特征及破坏过程。

Low-strength cemented tailings backfill(CTB)may be in the post-peak failure stage when controls ground pressure in backfill mining.The post-peak stress-strain curve characteristics and the acoustic emission(AE)parameters of CTB are closely related to the control of ground pressure.Therefore,uniaxial compression experiments and AE tests of CTB from unclassified tailings of Chengchao Iron Mine with cement-tailing ratio of 1:6 are conducted to obtain the stress-strain curve and the AE parameters.The post-peak stress-strain curve characteristics and failure process of CTB are analyzed based on AE energy rate and AE event.The result shows that the slope value of the post-peak stress-strain curve of CTB is negative,which decreases firstly,then increases and keeps a constant finally.The post-peak stress-strain curve could be divided into stage AB,stage BC and stage after C according to its slope variation.During stage AB,the stress-strain curve gradually becomes steeper and its slope value decreases with a convex sharp.The macroscopic cracks on the surface of the filling body increase gradually and the strength deterioration accelerates.The energy rate decreases dramatically,then increases rapidly and AE event location point concentrate partly.When the CTB enters the BC stage,the stress-strain curve becomes slow and its slope increase with a concave sharp.The macroscopic shear plain appears because of the expansion and convergence of shear cracks and the failure process becomes slower. The energy rate is high and decreases with AE event location points gathering into a strip.At the stage after C,the slope of the stress-strain curve keeps a constant.The shear plain slips and external load is supported by residual structure of CTB.Meanwhile,the energy rate and AE event reduce significantly.The post-peak AE parameters of CTB can well reflect its characteristics of stress-strain curve and the failure process.