深埋安山岩动态力学特性及破碎特征

Dynamic mechanical properties and crushing characteristics of deep⁃buried andesite

随着开采深度的增加,岩石力学参数随之发生改变,支护方式也应随之适时调整。为准确掌握基建矿山的岩石动态力学性能,以Jama铜矿的主要围岩安山岩为研究对象,开展了不同加载速度下的常规单轴霍普金森压杆(SHPB)试验,得到了安山岩的动态力学参数及破坏特征,并基于断裂力学理论,构建了考虑应变率的平均块度预测模型,并对冲击破碎后的碎块进行扫描电镜分析。试验结果表明:安山岩的动态压缩应力-应变曲线可分为4个阶段,压密阶段较静态曲线表现不明显。随应变率的提高,动态峰值强度及动态强度因子均呈线性增大趋势,单位体积吸能密度和质量破碎能耗均呈二次多项式规律的增长趋势;随新增比表面积的增大,吸能密度呈线性增大;预测模型理论值与试验值高度吻合;不同冲击速度下试件多以沿晶破坏为主,断口形貌较为复杂,相同放大倍数下随冲击载荷的增加,细观分形维数D_(e)呈线性正相关,可为后期自然崩落法底部结构爆破参数优化及工程应用提供一定的参考。

With the increase of mining depth,the rock mechanics parameters change and the support mode should be adjusted in time.For infrastructure mines,it is important to accurately obtain the dynamic mechanical properties of rock.In this paper,the main surrounding rock andesite in Jama Copper Mine is taken as the research object,and the conventional uniaxial split Hopkinson pressure bar(SHPB)tests under different loading speeds are carried out,and the dynamic mechanical parameters and failure characteristics of andesite are obtained.Based on the theo⁃ry of fracture mechanics,the average fragmentation prediction model considering strain rate is developed,and the fragments after impact crushing are scanned by scanning electron microscope.The results show that the dynamic compressive stress-strain curve of andesite can be divided into four stages,and the compaction stage is not obvious when compared to the static curve.The dynamic peak strength and dynamic strength factor increase linearly with the increase of strain rate.The energy absorption density per unit volume and mass crushing energy consumption increase quadratically with the increase of strain rate,and the energy absorption density is linearly positively correlated with the increase of new specific surface area.A dynamic fragmentation prediction model considering strain rate is established,and the theoretical prediction is in a good agreement with the experiment.The andesite specimens under different impact velocities are mainly intergranular failure,and the fracture morphology is fairly complex.Under the same magnification,the mesoscopic fractal dimension D_(e)is linearly positively correlated with the increase of impact load.This research can provide a certain reference for the optimization of blasting parameters and engineering application of the bottom structure of the natural caving method.