冲击荷载下全尾砂胶结充填体断裂特性与能耗特征分析

Analysis of fracture characteristics and energy consumption of full tailings cemented backfill under impact load

为研究冲击荷载作用下全尾砂胶结充填体断裂特性及能耗特征,借助分离式霍普金森压杆(split Hopkinson pressure bar,SHPB)试验系统,开展中等应变率下不同灰砂比充填体的单轴冲击试验。结果表明:灰砂比相同时,充填体的峰前应变能、吸收能、峰前应变能密度及吸能密度均随入射能的增加呈指数函数递增规律;当入射能小于16 J时,灰砂比为1︰6的充填体的吸能密度、峰前应变能密度、吸收能及峰前应变能比灰砂比1︰4与1︰8的更大;相同峰值强度、入射能、峰前应变能及吸收能下,充填体的断裂韧度均随灰砂比的增大而逐渐增大;充填体的断裂韧度随着动态峰值强度、吸能密度及峰前应变能密度的增加呈线性增长,而随着入射能、峰前应变能及吸收能的增加呈指数函数递增规律,灰砂比为1︰4的充填体断裂韧度随吸能密度、峰前应变能密度的增幅是灰砂比为1︰6和1︰8的2~3倍;基于应变能密度、能耗与应变的增长规律,可将充填体的损伤破坏演化过程划分为非线性压密、线弹性变形、弹塑性变形、峰后破坏4个阶段;通过对充填体试验结果回归分析,从能耗角度得出充填体断裂韧度的计算公式,可为井下充填体的稳定性分析提供参考。

In order to study the fracture characteristics and energy consumption characteristics of the fully tailings cemented backfill under impact loading,uniaxial impact tests on fillers with different cement-sand ratios at moderate strain rates were carried out with the help of a split Hopkinson pressure bar(SHPB)test system.The results show that the pre-peak strain energy,absorbed energy,prepeak strain energy density and absorbed energy density of the backfill body all increase exponentially as increase of incident energy when the cement-sand ratio is the same.When the incident energy is less than 16 J,the absorbed energy density,pre-peak strain energy density,absorbed energy and pre-peak strain energy of the backfill body with the cement-sand ratio of 1:6 are greater than those of the cement-sand ratio of 1:4 and 1:8.The fracture toughness of the backfill body gradually grows with the increase of the cement-sand ratio for the same peak strength,incident energy,pre-peak strain energy and absorption energy.The fracture toughness of the backfill body increases linearly with the increase of dynamic peak strength,absorbed energy density and pre-peak strain energy density,and increases exponentially with the increase of incident energy,pre-peak strain energy and absorbed energy.The increase of fracture toughness with energy absorption density and pre-peak strain energy density of the filled body with cement-sand ratio of 1:4 is two to three times that of cement-sand ratios of 1:6 and 1:8.Based on the growth law of strain energy density,energy consumption and strain,the damage and failure evolution process of the backfill can be divided into four stages:nonlinear compression,linear elastic deformation,elasto-plastic deformation and post-peak damage.Through regression analysis of the backfill body test results,a calculation formula for the fracture toughness is derived from the perspective of energy consumption,which can provide a reference for the stability analysis of the underground backfill body.