高静荷载下卸载速率对岩石动力学特性及破坏模式的影响
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摘要
为研究深部岩石的动力学特征及破坏模式受卸载速率影响而变化的规律,基于深部岩石开挖工程面临的"高静载卸荷过程中受冲击扰动"的力学环境,利用改进的动静组合加载SHPB试验系统开展高轴压卸荷频繁冲击扰动试验。试验一个完整循环过程为:先参考深部蛇纹岩的单轴抗压强度施加轴向荷载,再以一定速率卸载至预加轴压值的50%时施加0.4 MPa的冲击荷载,最后停止卸荷。试验研究结果表明:岩石的动态应力–应变曲线及其包络线都经历短暂的直线段进入非线性发展阶段,说明卸载冲击扰动过程中岩样主要发生塑性变形;卸载速率的增加导致岩样对冲击荷载的延缓让力效应明显,造成岩石均值强度及承受的累计扰动冲击次数增加,且引起岩石发生脆性、延性互相转化的现象;预加载轴压、卸荷速率的增加,导致破坏岩块块度呈增大的趋势发展,且前者促使岩样以拉伸破坏为主,后者促使岩样以剪切破坏为主。
In order to study effects of the unloading rate on the dynamic characteristics and failure modes of deep rock,the improved SHPB test system combined with dynamic and static loadings,which can simulate the mechanical environment of deep rock excavations subjected to impact disturbance during high static unloading process,was used to carry out the frequent disturbance test under high axial pressure and unloading. The samples were applied by a complete cycle loading. Specifically,a sample was firstly applied with a given axial load referring to the uniaxial compressive strength of deep serpentine,then unloaded till to 50% of the axial load at a certain rate and at the moment,an impact load of 0.4 MPa was exerted,and finally the unloading process terminated. The test results show that the dynamic stress-strain curve of rock and its envelope have a stage of nonlinear development following a short straight line stage,which indicates that plastic deformation of rock specimen plays a dominate role during impact disturbance and unloading. The increase of the unloading rate leads to obvious delaying effect of rock specimen on the impact load,resulting in an increase of rock′s mean strength and the cumulative number of impact disturbance,and causing the interconvertible phenomenon of brittle and ductility. With increasing the pre-axial stress and the unloading rate,the fragmentation of damaged rock mass increases,and they lead to tensile and shear failures,respectively.
In order to study effects of the unloading rate on the dynamic characteristics and failure modes of deep rock,the improved SHPB test system combined with dynamic and static loadings,which can simulate the mechanical environment of deep rock excavations subjected to impact disturbance during high static unloading process,was used to carry out the frequent disturbance test under high axial pressure and unloading. The samples were applied by a complete cycle loading. Specifically,a sample was firstly applied with a given axial load referring to the uniaxial compressive strength of deep serpentine,then unloaded till to 50% of the axial load at a certain rate and at the moment,an impact load of 0.4 MPa was exerted,and finally the unloading process terminated. The test results show that the dynamic stress-strain curve of rock and its envelope have a stage of nonlinear development following a short straight line stage,which indicates that plastic deformation of rock specimen plays a dominate role during impact disturbance and unloading. The increase of the unloading rate leads to obvious delaying effect of rock specimen on the impact load,resulting in an increase of rock′s mean strength and the cumulative number of impact disturbance,and causing the interconvertible phenomenon of brittle and ductility. With increasing the pre-axial stress and the unloading rate,the fragmentation of damaged rock mass increases,and they lead to tensile and shear failures,respectively.
引文
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[8]YANG S Q,JING H W,XU T.Mechanical behavior and failure analysis of brittle sandstone specimens containing combined flaws under uniaxial compression[J].Journal of Central South University,2014,21(5):2 059-2 073.
[9]QIU J D,LI D Y,LI X B.Dynamic failure of a phyllite with a low degree of metamorphism under impact Brazilian test[J].International Journal of Rock Mechanics and Mining Sciences,2017,94:10-17.
[10]ZHOU Z L,ZHAO Y,JIANG Y H,et al.Dynamic behavior of rock during its post failure stage in SHPB tests[J].Transactions of Nonferrous Metals Society of China,2017,27(1):184-196.
[11]LI X B,ZOU Y G,ZHOU Z L.Numerical simulation of the rock SHPB test with a special shape striker based on the discrete element method[J].Rock Mechanics and Rock Engineering,2014,47(5):1 693-1 709.
[12]ZHANG X L,JIAO Y Y,MA J F.Simulation of rock dynamic failure using discontinuous numerical approach[J].Computers and Geotechnics,2018,96:160-166.
[13]DU H B,DAI F,XIA K W,et al.Numerical investigation on the dynamic progressive fracture mechanism of cracked chevron notched semi-circular bend specimens in split Hopkinson pressure bar tests[J].Engineering Fracture Mechanics,2017,184:202-217.
[14]QIU J D,LI D Y,LI X B,et al.Dynamic fracturing behavior of layered rock with different inclination angles in SHPB tests[J].Shock and Vibration,2017:1-12.
[15]LI X B,ZHOU T,LI D Y,et al.Experimental and numerical investigations on feasibility and validity of prismatic rock specimen in SHPB[J].Shock and Vibration,2016:1-13.
[16]MALIKA A,CHAKRABORTYB T,RAOB K S.Strain rate effect on the mechanical behavior of basalt:Observations from static and dynamic tests[J].Thin-Walled Structures,2018,126(SI):127-137.
[17]ALAM M S,CHAKRABORTY T,MATSAGAR V,et al.Characterization of kota sandstone under different strain rates in uniaxial loading[J].Geotechnical and Geological Engineering,2015,33(1):143-152.
[18]LINDHOLM U S,YEAKLEY L M,NAGY A.Dynamic strength and fracture properties of dresser basalt[J].International of Journal of Rock Mechanics and Mining Sciences,1974,11(5):181-191.
[19]宋希贤,左宇军,朱万成.动力扰动下侧压系数对卸压孔与锚杆支护的研究[J].地下空间与工程学报,2013,9(5):1 076-1 081.(SONG Xixian,ZUO Yujun,ZHU Wancheng.Effect of Lateral Pressure Coefficients on Pressure-released Hole Combined Support with rockbolt under dynamic disturbance[J].Chinese Journal of Underground Space and Engineering,2013,9(5):1 076-1 081.(in Chinese))
[20]宋希贤,左宇军,王宪.动力扰动下深部巷道卸压孔与锚杆联合支护的数值模拟[J].中南大学学报:自然科学版,2014,45(9):3 158-3 165.(SONG Xixian,ZUO Yujun,WANG Xian.Numerical simulation of pressure-released hole combined support with rockbolt in deep roadway with dynamic disturbance[J].Journal of Central South University:Science and Technology,2014,45(9):3 158-3 165.(in Chinese)))
[21]马振乾,姜耀东,杨英明,等.动力扰动下单孔夹片式锚具滑移机制研究[J].岩石力学与工程学报,2016,35(增1):3 042-3 050.(MAZhenqian,JIANG Yaodong,YANG Yingming,et al.Slip mechanism of wedge and barrel anchorages under dynamic disturbance[J].Chinese Journal of Rock Mechanics and Engineering,2016,35(Supp.1):3 042-3 050.(in Chinese))
[22]康红普,王金华,林健.高预应力强力支护系统及其在深部巷道中的应用[J].煤炭学报,2007,32(12):1 233-1 238.(KANGHongpu,WANG Jinhua,LIN Jian.High pretensioned stress and intensive bolting system and its application in deep roadways[J].Journal of China Coal Society,2007,32(12):1 233-1 238.(in Chinese))
[23]黄万朋,高延法,王军.扰动作用下深部岩巷长期大变形机制及控制技术[J].煤炭学报,2014,39(5):822-828.(HUANG Wanpeng,GAO Yanfa,WANG Jun.Deep rock tunnel′s long large deformation mechanism and control technology under disturbance effects[J].Journal of China Coal Society,2014,39(5):822-828.(in Chinese))
[24]CHEN R,YAO W,LU F.Evaluation of the stress equilibrium condition in axially constrained triaxial SHPB test[J].Experimental Mechanics,2018,58(3):527-531.
[25]SONG B,CHEN W.Dynamic stress equilibration in split Hopkinson pressure bar tests on soft materials[J].Experimental Mechanics,2004,44(3):300-312.
[26]叶洲元,赵伏军,周子龙.动静组合载荷下卸荷岩石力学特性分析[J].岩土工程学报,2013,35(3):454-459.(YE Zhouyuan,ZHAOFujun,ZHOU Zilong.Mechanical characteristics of unloading rock under coupled dynamic and static loads[J].Chinese Journal of Geotechnical Engineering,2013,35(3):454-459.(in Chinese))
[27]殷志强,李夕兵,尹土兵,等.高应力岩石围压卸载后动力扰动的临界破坏特性[J].岩石力学与工程学报,2012,31(7):1 355-1 362.(YIN Zhiqiang,LI Xibing,YIN Tubing,et al.Critical failure characteristics of high stress rock induced by impact disturbance under confining[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(7):1 355-1 362.(in Chinese))
[28]宫凤强,李夕兵,刘希灵.三维动静组合加载下岩石力学特性试验初探[J].岩石力学与工程学报,2011,30(6):1 178-1 190.(GONGFengqiang,LI Xibing,LIU Xiling.Preliminary experimental study of characteristics of rock subjected to 3D coupled static and dynamic loads[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(6):1 178-1 190.(in Chinese))
[29]唐礼忠,王春,程露萍,等.一维静载及循环冲击共同作用下矽卡岩力学特性试验研究[J].中南大学学报:自然科学版,2015,46(10):3 898-3 908.(TANG Lizhogn,WANG Chun,CHENGLuping,et al.Experimental study of mechanical characteristics of skarn under one-dimensional coupled static and cyclic impact loads[J].Journal of Central South University:Science and Technology,2015,46(10):3 898-3 908.(in Chinese))
[30]王春,唐礼忠,程露萍,等.一维静载与频繁扰动共同作用下含铜蛇纹岩动力学特性[J].振动与冲击,2016,35(9):219-226.(WANG Chun,TANG Lizhong,CHENG Luping,et al.Dynamic characteristics of copper-bearing serpentine under combined action of one-dimensional static load and frequent disturbance[J].Journal of Vibration and Shock,2016,35(9):219-226.(in Chinese))
[2]谢和平.“深部岩体力学与开采理论”研究构想与预期成果展望[J].工程科学与技术,2017,49(2):1-16.(XIE Heping.Research framework and anticipated results of deep rock mechanics and mining theory[J].Advanced Engineering Sciences,2017,49(2):1-16.(in Chinese))
[3]宫凤强,张乐,李夕兵,等.不同预静载硬岩在动力扰动下断裂特性的试验研究[J].岩石力学与工程学报,2017,36(8):1 841-1 853.(GONG Fengqiang,ZHANG Le,LI Xibing,et al.Experimental study on fracture behaviors of hard rock under dynamic disturbance with different pre-static loads[J].Chinese Journal of Rock Mechanics and Engineering,2017,36(8):1 841-1 853.(in Chinese))
[4]周宗红,章雅琦,杨安国,等.白云岩三维动静组合加载力学特性试验研究[J].煤炭学报,2015,40(5):1 030-1 036.(ZHOUZonghong,ZHANG Yaqi,YANG Anguo,et al.Experimental study on mechanical characteristics of dolomite under three-dimensional coupled static-dynamic loading[J].Journal of China Coal Society,2015,40(5):1 030-1 036.(in Chinese))
[5]李晓锋,李海波,刘凯,等.冲击荷载作用下岩石动态力学特性及破裂特征研究[J].岩石力学与工程学报,2017,36(10):2 393-2 405.(LI Xiaofeng,LI Haibo,LIU Kai,et al.Dynamic properties and fracture characteristics of rocks subject to impact loading[J].Chinese Journal of Rock Mechanics and Engineering,2017,36(10):2 393-2 405.(in Chinese))
[6]ZHANG Q B,ZHAO J.Effect of loading rate on fracture toughness and failure micromechanisms in marble[J].Engineering Fracture Mechanics,2013,102:288-309.
[7]李地元,韩震宇,孙小磊,等.含预制裂隙大理岩SHPB动态力学破坏特性试验研究[J].岩石力学与工程学报,2017,36(12):2 872-2 883.(LI Diyuan,HAN Zhenyu,SUN Xiaolei,et al.Characteristics of dynamic failure of marble with artificial flaws under split Hopkinson pressure bar tests[J].Chinese Journal of Rock Mechanics and Engineering,2017,36(12):2 872-2 883.(in Chinese))
[8]YANG S Q,JING H W,XU T.Mechanical behavior and failure analysis of brittle sandstone specimens containing combined flaws under uniaxial compression[J].Journal of Central South University,2014,21(5):2 059-2 073.
[9]QIU J D,LI D Y,LI X B.Dynamic failure of a phyllite with a low degree of metamorphism under impact Brazilian test[J].International Journal of Rock Mechanics and Mining Sciences,2017,94:10-17.
[10]ZHOU Z L,ZHAO Y,JIANG Y H,et al.Dynamic behavior of rock during its post failure stage in SHPB tests[J].Transactions of Nonferrous Metals Society of China,2017,27(1):184-196.
[11]LI X B,ZOU Y G,ZHOU Z L.Numerical simulation of the rock SHPB test with a special shape striker based on the discrete element method[J].Rock Mechanics and Rock Engineering,2014,47(5):1 693-1 709.
[12]ZHANG X L,JIAO Y Y,MA J F.Simulation of rock dynamic failure using discontinuous numerical approach[J].Computers and Geotechnics,2018,96:160-166.
[13]DU H B,DAI F,XIA K W,et al.Numerical investigation on the dynamic progressive fracture mechanism of cracked chevron notched semi-circular bend specimens in split Hopkinson pressure bar tests[J].Engineering Fracture Mechanics,2017,184:202-217.
[14]QIU J D,LI D Y,LI X B,et al.Dynamic fracturing behavior of layered rock with different inclination angles in SHPB tests[J].Shock and Vibration,2017:1-12.
[15]LI X B,ZHOU T,LI D Y,et al.Experimental and numerical investigations on feasibility and validity of prismatic rock specimen in SHPB[J].Shock and Vibration,2016:1-13.
[16]MALIKA A,CHAKRABORTYB T,RAOB K S.Strain rate effect on the mechanical behavior of basalt:Observations from static and dynamic tests[J].Thin-Walled Structures,2018,126(SI):127-137.
[17]ALAM M S,CHAKRABORTY T,MATSAGAR V,et al.Characterization of kota sandstone under different strain rates in uniaxial loading[J].Geotechnical and Geological Engineering,2015,33(1):143-152.
[18]LINDHOLM U S,YEAKLEY L M,NAGY A.Dynamic strength and fracture properties of dresser basalt[J].International of Journal of Rock Mechanics and Mining Sciences,1974,11(5):181-191.
[19]宋希贤,左宇军,朱万成.动力扰动下侧压系数对卸压孔与锚杆支护的研究[J].地下空间与工程学报,2013,9(5):1 076-1 081.(SONG Xixian,ZUO Yujun,ZHU Wancheng.Effect of Lateral Pressure Coefficients on Pressure-released Hole Combined Support with rockbolt under dynamic disturbance[J].Chinese Journal of Underground Space and Engineering,2013,9(5):1 076-1 081.(in Chinese))
[20]宋希贤,左宇军,王宪.动力扰动下深部巷道卸压孔与锚杆联合支护的数值模拟[J].中南大学学报:自然科学版,2014,45(9):3 158-3 165.(SONG Xixian,ZUO Yujun,WANG Xian.Numerical simulation of pressure-released hole combined support with rockbolt in deep roadway with dynamic disturbance[J].Journal of Central South University:Science and Technology,2014,45(9):3 158-3 165.(in Chinese)))
[21]马振乾,姜耀东,杨英明,等.动力扰动下单孔夹片式锚具滑移机制研究[J].岩石力学与工程学报,2016,35(增1):3 042-3 050.(MAZhenqian,JIANG Yaodong,YANG Yingming,et al.Slip mechanism of wedge and barrel anchorages under dynamic disturbance[J].Chinese Journal of Rock Mechanics and Engineering,2016,35(Supp.1):3 042-3 050.(in Chinese))
[22]康红普,王金华,林健.高预应力强力支护系统及其在深部巷道中的应用[J].煤炭学报,2007,32(12):1 233-1 238.(KANGHongpu,WANG Jinhua,LIN Jian.High pretensioned stress and intensive bolting system and its application in deep roadways[J].Journal of China Coal Society,2007,32(12):1 233-1 238.(in Chinese))
[23]黄万朋,高延法,王军.扰动作用下深部岩巷长期大变形机制及控制技术[J].煤炭学报,2014,39(5):822-828.(HUANG Wanpeng,GAO Yanfa,WANG Jun.Deep rock tunnel′s long large deformation mechanism and control technology under disturbance effects[J].Journal of China Coal Society,2014,39(5):822-828.(in Chinese))
[24]CHEN R,YAO W,LU F.Evaluation of the stress equilibrium condition in axially constrained triaxial SHPB test[J].Experimental Mechanics,2018,58(3):527-531.
[25]SONG B,CHEN W.Dynamic stress equilibration in split Hopkinson pressure bar tests on soft materials[J].Experimental Mechanics,2004,44(3):300-312.
[26]叶洲元,赵伏军,周子龙.动静组合载荷下卸荷岩石力学特性分析[J].岩土工程学报,2013,35(3):454-459.(YE Zhouyuan,ZHAOFujun,ZHOU Zilong.Mechanical characteristics of unloading rock under coupled dynamic and static loads[J].Chinese Journal of Geotechnical Engineering,2013,35(3):454-459.(in Chinese))
[27]殷志强,李夕兵,尹土兵,等.高应力岩石围压卸载后动力扰动的临界破坏特性[J].岩石力学与工程学报,2012,31(7):1 355-1 362.(YIN Zhiqiang,LI Xibing,YIN Tubing,et al.Critical failure characteristics of high stress rock induced by impact disturbance under confining[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(7):1 355-1 362.(in Chinese))
[28]宫凤强,李夕兵,刘希灵.三维动静组合加载下岩石力学特性试验初探[J].岩石力学与工程学报,2011,30(6):1 178-1 190.(GONGFengqiang,LI Xibing,LIU Xiling.Preliminary experimental study of characteristics of rock subjected to 3D coupled static and dynamic loads[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(6):1 178-1 190.(in Chinese))
[29]唐礼忠,王春,程露萍,等.一维静载及循环冲击共同作用下矽卡岩力学特性试验研究[J].中南大学学报:自然科学版,2015,46(10):3 898-3 908.(TANG Lizhogn,WANG Chun,CHENGLuping,et al.Experimental study of mechanical characteristics of skarn under one-dimensional coupled static and cyclic impact loads[J].Journal of Central South University:Science and Technology,2015,46(10):3 898-3 908.(in Chinese))
[30]王春,唐礼忠,程露萍,等.一维静载与频繁扰动共同作用下含铜蛇纹岩动力学特性[J].振动与冲击,2016,35(9):219-226.(WANG Chun,TANG Lizhong,CHENG Luping,et al.Dynamic characteristics of copper-bearing serpentine under combined action of one-dimensional static load and frequent disturbance[J].Journal of Vibration and Shock,2016,35(9):219-226.(in Chinese))