循环冲击对围压作用下砂岩特征的影响
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摘要
利用带围压装置的分离式霍普金森压杆系统对砂岩试样进行不同围压下的循环冲击试验,探讨了冲击应变波的波形特征,并对围压与应力应变、损伤因子等物理量间的关系进行了分析.结果表明:透射波在砂岩试件中传播时存在明显的非线性,并可计算得到砂岩中冲击波的形成距离;砂岩在无围压作用下发生脆性破坏,有围压时表现出明显的弹塑性特征.当围压一定时,应力-应变曲线的上升段斜率随冲击次数增加而减小;当围压增大时,不同冲击次数下的应力-应变曲线差异减小;砂岩损伤因子随平均应变率增大呈幂函数增长,且二者均随围压增加呈现出良好的规律性.
Based on the split Hopkinson pressure bar system with a confining pressure device,the cyclic impact tests on sandstone specimens under different confining pressures were carried out.The waveform characteristics of strain waves were analyzed,as well as the relationship among confining pressures, stress, strain and damage factors. It is demonstrates that the sandstone behaves nonlinear response under impact loads.The shockwave distance of the explored sandstone is calculated.Furthermore,sandstone behaves brittle failure when loaded without confining, but it shows evident elastic-plastic characteristic under confining pressures. When the confining pressure is constant, the slope of the stress-strain curve decreases with the increase of impact number.And a higher confining pressure makes smaller the difference in the stress-strain curves of different impact numbers.A power function relationship exists between damage factor and average strain rate,and both of them change regularly with confining pressures.
Based on the split Hopkinson pressure bar system with a confining pressure device,the cyclic impact tests on sandstone specimens under different confining pressures were carried out.The waveform characteristics of strain waves were analyzed,as well as the relationship among confining pressures, stress, strain and damage factors. It is demonstrates that the sandstone behaves nonlinear response under impact loads.The shockwave distance of the explored sandstone is calculated.Furthermore,sandstone behaves brittle failure when loaded without confining, but it shows evident elastic-plastic characteristic under confining pressures. When the confining pressure is constant, the slope of the stress-strain curve decreases with the increase of impact number.And a higher confining pressure makes smaller the difference in the stress-strain curves of different impact numbers.A power function relationship exists between damage factor and average strain rate,and both of them change regularly with confining pressures.
引文
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[2]DEY K,MURTHY V M S R.Prediction of blast-induced overbreak from uncontrolled burn-cut blasting in tunnels driven through medium rock class[J].Tunneling and Underground Space Technology,2012,28(1):49-56.
[3]HAO H,WU C H,ZHOU Y X.Numerical analysis of blast-induced stress waves in a rock mass with anisotropic continuum damage models,PartⅠ:equivaient material property approach[J].Rock Mechanics and Rock Engineering,2002,35(2):79-94.
[4]刘德克.单轴冲击及一维动静组合加载下红砂岩力学特征研究[D].昆明:昆明理工大学图书馆,2015.
[5]黎立云,徐志强,谢和平,等.不同冲击速度下岩石破坏能量规律的实验研究[J].煤炭学报,2011,36(12):2007-2011.
[6]LI S H,ZHU W C,NIU L L,et al.Dynamic characteristics of green sandstone subjected to repetitive impact loading:phenomena and mechanisms[J].Rock Mechanics and Rock Engineering,2018,51(6):1921-1936.
[7]吕晓聪,许金余,赵德辉,等.冲击荷载作用下砂岩动态力学性能的围压效应研究[J].工程力学,2011,28(1):138-144.
[8]刘少虹,毛德兵,齐庆新,等.动静加载下组合煤岩的应力波传播机制与能量耗散[J].煤炭学报,2014,39(S1):15-22.
[9]LI X F,ZHANG Q B,LI H B,et al.Grain-based discrete element method(GB-DEM)modelling of multi-scale fracturing in rocks under dynamic loading[J].Rock Mechanics and Rock Engineering,2018,51(12):3785-3817.
[10]HONG L,ZHOU Z L,YIN T B,et al.Energy consumption in rock fragmentation at intermediate strain rate[J].J Cent South Univ Technol,2009,16(4):677-682.
[11]钱祖文.非线性声学[M].北京:科学出版社,2009.
[12]田家勇,满元鹏,齐辉.岩石三阶弹性模量的高精度测定研究[J].岩石力学与工程学报,2010,29(S2):3558-3561.
[13]江益辉.冲击荷载作用下岩石峰后损伤破坏特性研究[D].长沙:中南大学图书馆,2014.
[14]林大能,陈寿如.循环冲击荷载作用下岩石损伤规律的试验研究[J].岩石力学与工程学报,2005,24(22):4094-4098.