卸荷时间对圆形巷道围岩开裂及径向应力波传播影响的数值模拟
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摘要
采用提出的连续-非连续方法,研究了卸荷时间(卸荷快慢)对圆形巷道围岩开裂、径向应力波传播及围岩径向应力随时间演变规律的影响。该方法借鉴了拉格朗日元法、变形体离散元法及虚拟裂纹模型的思想。首先,研究了卸荷时间对围岩开裂的影响;然后,研究了卸荷时间对径向应力波传播的影响;最后,研究了卸荷时间对围岩径向应力随时间演变规律的影响。结果表明:卸荷越快,围岩中产生的裂纹越多,最大不平衡力越大,波动越剧烈。增加卸荷时间,开挖边界附近的开裂位置由连续分布向间隔分布转变:当卸荷时间较短时,开挖边界附近围岩呈现连续分布的开裂形态,与这些位置的最大主应力均超过抗拉强度引起拉裂有关;当卸荷时间适中时,围岩呈现出与V形坑类似的开裂形态,可能与这些位置存在剪应力有关。卸荷越快,处于扰动区(径向压应力下降区)内的应力环越多,越清晰,围岩径向应力波动越剧烈,所达到的最大径向拉应力越大或最小径向压应力越小。
In this paper,the influence of unloading time(unloading rate)on the cracking,radial stress wave propagation,and radial stress evolution in a circular tunnel surrounding rock was studied by use of the continuum-discontinuum method proposed by the authors.This method was based on the Lagrangian element method,deformational discrete element method,and fictitious crack model.The influence of unloading time on the cracking,radial stress wave propagation,and radial stress evolution of the surrounding rock was investigated successively.A shorter unloading time was accompanied by more cracks,and a greater and more intense fluctuation of the maximum unbalanced force in the surrounding rock.The crack near the excavation boundary changed from a continuous distribution to a discontinuous distribution with the increase of the unloading time.When the unloading time was short,the crack distribution in the surrounding rock was continuous,which was because that the maximum principal stresses at these locations exceeded the tension strength.When the unloading time was moderate,the crack distribution in the surrounding rock was similar to V-shaped notches,which may be related to the presence of shear stresses at these locations.At a shorter unloading time,the number of radial stress rings in the disturbed zone(i.e.,the decreasing zone of radial compressive stresses)was greater and clearer,the fluctuation of radial stresses in the surrounding rock was more evident,and the maximum radial tensile stresses(or minimum radial compressive stresses)were larger(respectively,smaller).
In this paper,the influence of unloading time(unloading rate)on the cracking,radial stress wave propagation,and radial stress evolution in a circular tunnel surrounding rock was studied by use of the continuum-discontinuum method proposed by the authors.This method was based on the Lagrangian element method,deformational discrete element method,and fictitious crack model.The influence of unloading time on the cracking,radial stress wave propagation,and radial stress evolution of the surrounding rock was investigated successively.A shorter unloading time was accompanied by more cracks,and a greater and more intense fluctuation of the maximum unbalanced force in the surrounding rock.The crack near the excavation boundary changed from a continuous distribution to a discontinuous distribution with the increase of the unloading time.When the unloading time was short,the crack distribution in the surrounding rock was continuous,which was because that the maximum principal stresses at these locations exceeded the tension strength.When the unloading time was moderate,the crack distribution in the surrounding rock was similar to V-shaped notches,which may be related to the presence of shear stresses at these locations.At a shorter unloading time,the number of radial stress rings in the disturbed zone(i.e.,the decreasing zone of radial compressive stresses)was greater and clearer,the fluctuation of radial stresses in the surrounding rock was more evident,and the maximum radial tensile stresses(or minimum radial compressive stresses)were larger(respectively,smaller).
引文
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[8]周储伟,潘清.模拟裂纹扩展的一种有限元局部动态子划分方法[J].计算力学学报,2012,29(4):499-504.Zhou Ch W,Pan Q.A dynamic sub-partition strategy of finite element for simulation of crack propagation[J].Chinese Journal of Computational Mechanics,2012,29(4):499-504.(in Chinese)
[9]Cundall P A,Hart R D.Numerical modelling of discontinua[J].Engineering Computations,1992,9(2):101-113.
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[13]Rockfield Software Ltd..ELFEN 2D/3D numerical modelling package[R].Swansea,UK:Rockfield Software Ltd.,2004.
[14]Mahabadi O K,Lisjak A,Munjiza A,et al.Y-Geo:new combined finite-discrete element numerical code for geomechanical applications[J].American Society of Civil Engineers,2012,12(6):676-688.
[15]Lisjak A,Grasselli G.A review of discrete modeling techniques for fracturing processes in discontinuous rock masses[J].Journal of Rock Mechanics and Geotechnical Engineering,2014,6(4):301-314.
[16]Lisjak A,Figi D,Grasselli G.Fracture development around deep underground excavations insights from FDEM modelling[J].Journal of Rock Mechanics and Geotechnical Engineering,2014,6(6):493-505.
[17]王学滨.拉格朗日元方法、变形体离散元方法及虚拟裂纹模型耦合的连续-非连续介质分析方法研究[R].北京:中国矿业大学(北京),2015.Wang X B.A method for continuum-discontinuum medium based on the coupled Lagrangian element method,deformational discrete element method and fictitious crack model[R].Beijing:China University of Mining and Technology(Beijing),2015.(in Chinese)
[18]Wang X B,Ma B,Pan Y Sh.Numerical simulation of stress wave propagation,cracking and collapsing for models containing circular and rectangular tunnels under excavation and displacement-controlled loading[C]//Proceedings of 35th International Conference on Ground Control in Mining(China,2016)-The Theory and Technical Progress on Ground Control in Mining.Beijing:China Coal Industry Publishing House,2016:99-107.
[19]郭翔,王学滨,白雪元,等.加载方式及抗拉强度对巴西圆盘试验影响的数值模拟[J].岩土力学,2017,38(1):1-8.Guo X,Wang X B,Bai X Y,et al.Numerical simulation of effects of loading types and tensile strengths on Brazilian disk test[J].Rock and Soil Mechanics,2017,38(1):1-8.(in Chinese)
[20]王涛,熊将,郭武祥,等.地震荷载作用下地下厂房围岩稳定的离散元计算方法研究[J].长江科学院院报,2009,26(12):62-66.Wang T,Xiong J,Guo W X,et al.Research on stability of rock mass around underground powerhouse cavern by discrete element method under earthquake[J].Journal of Yangtze River Scientific Research Institute,2009,26(12):62-66.(in Chinese)
[21]王学滨,潘一山,伍小林.不同强度岩石中开挖圆形巷道的局部化过程模拟[J].防灾减灾工程学报,2010,30(2):123-129.Wang X B,Pan Y Sh,Wu X L.Numerical simulation of strain localization processes of a excavation circular tunnel with different rock strengths[J].Journal of Disaster Prevention and Mitigation Engineering,2010,30(2):123-129.(in Chinese)
[2]刘祥鑫,梁正召,张艳博,等.卸荷诱发巷道模型岩爆的发生机理实验研究[J].工程地质学报,2016,24(5):965-975.Liu X X,Liang Zh Zh,Zhang Y B,et al.Unloading test for rockburst mechanism in tunnel model[J].Journal of Engineering Geology,2016,24(5):965-975.(in Chinese)
[3]刘国锋,冯夏庭,江权,等.白鹤滩大型地下厂房开挖围岩片帮破坏特征、规律及机制研究[J].岩石力学与工程学报,2016,35(5):865-878.Liu G F,Feng X T,Jiang Q,et al.Failure characteristics,laws and mechanisms of rock spalling in excavation of large-scale underground powerhouse caverns in Baihetan[J].Chinese Journal of Rock Mechanics and Engineering,2016,35(5):865-878.(in Chinese)
[4]严鹏,卢文波,陈明,等.隧洞开挖过程初始地应力动态卸载效应研究[J].岩土工程学报,2009,31(12):1 888-1 894.Yan P,Lu W B,Chen M,et al.Effect of initial geostress dynamic unloading during tunnel excavation[J].Chinese Journal of Geotechnical Engineering,2009,31(12):1 888-1 894.(in Chinese)
[5]杨栋,李海波,夏祥,等.高地应力条件下爆破开挖诱发围岩损伤的特性研究[J].岩土力学,2014,35(4):1 110-1 116,1 122.Yang D,Li H B,Xia X,et al.Study of blasting-induced dynamic damage of tunnel surrounding rocks under high in-situ stress[J].Rock and Soil Mechanics,2014,35(4):1 110-1 116,1 122.(in Chinese)
[6]王汉鹏,薛俊华,李建明,等.隧洞开挖围岩动态卸载响应特征模拟研究[J].岩土力学,2015,36(5):1 481-1 487.Wang H P,Xue J H,Li J M,et al.Simulation of dynamic response of surrounding rock under the tunneling-induced unloading[J].Rock and Soil Mechanics,2015,36(5):1 481-1 487.(in Chinese)
[7]张楚汉.论岩石、混凝土离散-接触-断裂分析[J].岩石力学与工程学报,2008,27(2):217-235.Zhang Ch H.Discrete-contact-fracture analysis of rock and concrete[J].Chinese Journal of Rock Mechanics and Engineering,2008,27(2):217-235.(in Chinese)
[8]周储伟,潘清.模拟裂纹扩展的一种有限元局部动态子划分方法[J].计算力学学报,2012,29(4):499-504.Zhou Ch W,Pan Q.A dynamic sub-partition strategy of finite element for simulation of crack propagation[J].Chinese Journal of Computational Mechanics,2012,29(4):499-504.(in Chinese)
[9]Cundall P A,Hart R D.Numerical modelling of discontinua[J].Engineering Computations,1992,9(2):101-113.
[10]Shi G H,Goodman R.Discontinuous deformation analysis-A new method for computing stress,strain and sliding of block systems[C]//Proceedings of the29th US Symposium on Rock Mechanics.Rotterdam:A.A.Balkema,1988.
[11]林志斌,李元海,高文艺,等.非构造应力下圆形巷道的内部变形破裂规律研究[J].采矿与安全工程学报,2015,32(3):491-497.Lin Zh B,Li Y H,Gao W Y,et al.Research on the law of internal deformation and cracking of circular tunnels under non-tectonic stress[J].Journal of Mining and Safety Engineering,2015,32(3):491-497.(in Chinese)
[12]张开,朱敏,张建强,等.深部软岩巷道开挖变形影响因素的数值分析[J].煤矿安全,2012,43(1):148-152.Zhang K,Zhu M,Zhang J Q,et al.Numerical analysis of physics influence factors of excavation deformation in deep soft rock[J].Safety in Coal Mines,2012,43(1):148-152.(in Chinese)
[13]Rockfield Software Ltd..ELFEN 2D/3D numerical modelling package[R].Swansea,UK:Rockfield Software Ltd.,2004.
[14]Mahabadi O K,Lisjak A,Munjiza A,et al.Y-Geo:new combined finite-discrete element numerical code for geomechanical applications[J].American Society of Civil Engineers,2012,12(6):676-688.
[15]Lisjak A,Grasselli G.A review of discrete modeling techniques for fracturing processes in discontinuous rock masses[J].Journal of Rock Mechanics and Geotechnical Engineering,2014,6(4):301-314.
[16]Lisjak A,Figi D,Grasselli G.Fracture development around deep underground excavations insights from FDEM modelling[J].Journal of Rock Mechanics and Geotechnical Engineering,2014,6(6):493-505.
[17]王学滨.拉格朗日元方法、变形体离散元方法及虚拟裂纹模型耦合的连续-非连续介质分析方法研究[R].北京:中国矿业大学(北京),2015.Wang X B.A method for continuum-discontinuum medium based on the coupled Lagrangian element method,deformational discrete element method and fictitious crack model[R].Beijing:China University of Mining and Technology(Beijing),2015.(in Chinese)
[18]Wang X B,Ma B,Pan Y Sh.Numerical simulation of stress wave propagation,cracking and collapsing for models containing circular and rectangular tunnels under excavation and displacement-controlled loading[C]//Proceedings of 35th International Conference on Ground Control in Mining(China,2016)-The Theory and Technical Progress on Ground Control in Mining.Beijing:China Coal Industry Publishing House,2016:99-107.
[19]郭翔,王学滨,白雪元,等.加载方式及抗拉强度对巴西圆盘试验影响的数值模拟[J].岩土力学,2017,38(1):1-8.Guo X,Wang X B,Bai X Y,et al.Numerical simulation of effects of loading types and tensile strengths on Brazilian disk test[J].Rock and Soil Mechanics,2017,38(1):1-8.(in Chinese)
[20]王涛,熊将,郭武祥,等.地震荷载作用下地下厂房围岩稳定的离散元计算方法研究[J].长江科学院院报,2009,26(12):62-66.Wang T,Xiong J,Guo W X,et al.Research on stability of rock mass around underground powerhouse cavern by discrete element method under earthquake[J].Journal of Yangtze River Scientific Research Institute,2009,26(12):62-66.(in Chinese)
[21]王学滨,潘一山,伍小林.不同强度岩石中开挖圆形巷道的局部化过程模拟[J].防灾减灾工程学报,2010,30(2):123-129.Wang X B,Pan Y Sh,Wu X L.Numerical simulation of strain localization processes of a excavation circular tunnel with different rock strengths[J].Journal of Disaster Prevention and Mitigation Engineering,2010,30(2):123-129.(in Chinese)