组合受力胶结充填体力学特性及能耗特征研究

一步骤胶结充填体为二步骤矿柱回采提供支撑,充填体由三轴受力转为单轴受力状态,其稳定性对采场安全至关重要。为此对比分析了单次(单轴)和二次(三轴加单轴)压缩对不同灰砂比胶结充填体的应力-应变曲线、强度特征、能耗特征及破坏模式。结果表明:单次比二次具有更明显压密阶段、更高线弹性阶段,增大围压使二次充填体压密阶段减小、线弹性阶段和屈服阶段延长、弹模增大;灰砂比1∶12直接进入线弹性变形阶段,但低围压各阶段水平大于高围压。1∶12峰值强度随围压增大而下降、1∶8先增后降、1∶4峰值强度与围压呈正相关,1∶8存在强度最优值;1∶4和1∶12两次充填体受围压影响较小,强度占比在26.05%~58.79%,1∶8则高达89.92%和93.51%。二次压缩和灰砂比降低造成充填体能量值下降,增大围压使峰前总能量占比上升、峰前应变能缓慢增加;1∶4和1∶8增大围压提高峰前储能极限,1∶12则先降后增。试样裂纹表现为平行和竖直,二次压缩使充填体破碎程度提高,增大围压维持完整性,试样二次压缩破坏路径沿首次路径发生,破坏位置发生在上部。

Study on mechanical properties and energy consumption characteristics of cemented backfill under combined loading

The one-step cemented backfill provides support for two-step pillar mining.The backfill changes from triaxial stress to uniaxial stress,and its stability is very important to stope safety.The stress-strain curves,strength characteristics,energy consumption characteristics,and failure modes of cemented backfill under single(uniaxial)and twice(triaxial plus uniaxial)compression with different cement-sand ratios are compared and analyzed.The results show that single filling has a more obvious compaction stage and higher linear elastic stage than twice filling.Increasing confining pressure makes the compaction stage decrease,linear elastic stage and yield stage extend,and elastic modulus increase.The lime sand ratio of 1∶12 directly enters the stage of linear elastic deformation,but the level of low confining pressure is higher than that of high confining pressure.The peak strength of 1∶12 decreases with the increase of confining pressure,increases first and then decreases at 1∶8,and peak intensity is positively correlated with confining pressure of 1∶4.The results show that the confining pressure has little influence on the strength of 1∶4 and 1∶12 backfill,and the strength ratio is 26.05%-58.79%,while the strength ratio is 89.92%and 93.51%at 1∶8.The results show that the energy value of backfill decreases with the decrease of twice compression and cement-sand ratio,and the proportion of total energy before peak increases and the strain energy before peak increases slowly with the increase of confining pressure;1∶4 and 1∶8,increase the confining pressure to improve the pre-peak energy storage limit,and 1∶12 first decreases and then increases.The results show that the cracks are parallel and vertical.The secondary compression increases the degree of fragmentation of the filling body,increases the confining pressure,and maintains integrity.The secondary compression failure path of the sample occurs along the first path,and the failure position occurs at the upper part.