裂隙岩石冻融循环下裂纹扩展特征研究
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摘要
高寒山区工程岩体往往在水和温差作用下,受到往复的冻融荷载作用,导致岩体裂纹扩展甚至破坏。通过开展-20～20℃范围内4类含裂隙岩石冻融循环试验,分析了不同岩性裂纹扩展类型和原因、裂纹扩展随冻融循环增加的全过程,并讨论了20次冻融循环下灰岩和红砂岩的裂纹扩展机理。结果表明:含裂隙岩石裂纹扩展可分为3种类型:沿上部裂隙尖端贯通岩桥、沿上部裂隙尖端环向扩展和无明显裂纹破坏;板岩的水平板理导致裂纹沿环向扩展,灰岩局部发育的软弱面使裂纹反倾下部裂隙扩展,花岗岩高强度和低孔隙率的特征使其难以在此次试验条件下产生宏观裂纹。断裂力学分析揭示了灰岩和红砂岩呈Ⅰ型裂纹扩展的原因,表明初始裂纹扩展方向与上部裂隙走向近似,裂纹扩展长度与岩石抗拉强度和断裂韧度有关。
In the alpine mountainous area,the rock mass is often subjected to reciprocating freeze-thaw load under the action of water and temperature difference,resulting in rock mass rupture or mechanical property degradation. By carrying out the freeze-thaw cycle test of four cracked rocks in the range of-20～ 20 ℃,the types and causes of different lithological crack propagation were discussed,the whole process of crack propagation with the increase of freeze-thaw cycles was analyzed,and the crack propagation mechanism of limestone and red sandstone under 20 freeze-thaw cycles was studied by using fracture mechanics. The results show that the crack propagation of cracked rock can be divided into three types,namely: perforating the rock bridge along the tip of the upper crack,circumferential extension along the tip of the upper crack and no obvious crack damage;the horizontal bedding of the slate causes the crack to expand along the circumference,the weak joint developed by the limestone causes the crack to propagate toward opposite direction from the lower crack,the high strength and low porosity of the granite make it difficult to produce macroscopic cracks under the test conditions. Fracture mechanics reveals the cause of I-type crack propagation in limestone and red sandstone,indicating that the initial crack propagation direction is similar to that of the upper fracture,and crack length is related to the tensile strength and fracture toughness of the rock.
In the alpine mountainous area,the rock mass is often subjected to reciprocating freeze-thaw load under the action of water and temperature difference,resulting in rock mass rupture or mechanical property degradation. By carrying out the freeze-thaw cycle test of four cracked rocks in the range of-20～ 20 ℃,the types and causes of different lithological crack propagation were discussed,the whole process of crack propagation with the increase of freeze-thaw cycles was analyzed,and the crack propagation mechanism of limestone and red sandstone under 20 freeze-thaw cycles was studied by using fracture mechanics. The results show that the crack propagation of cracked rock can be divided into three types,namely: perforating the rock bridge along the tip of the upper crack,circumferential extension along the tip of the upper crack and no obvious crack damage;the horizontal bedding of the slate causes the crack to expand along the circumference,the weak joint developed by the limestone causes the crack to propagate toward opposite direction from the lower crack,the high strength and low porosity of the granite make it difficult to produce macroscopic cracks under the test conditions. Fracture mechanics reveals the cause of I-type crack propagation in limestone and red sandstone,indicating that the initial crack propagation direction is similar to that of the upper fracture,and crack length is related to the tensile strength and fracture toughness of the rock.
引文
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[2]Arosio D,Longoni L,Mazza F,et al.Freeze-thaw cycle and rockfall monitoring[C]//Landslide Science and Practice,Berlin:Springer-Verlag,2013:385-390.
[3]黄勇.高寒山区岩体冻融力学行为及崩塌机制研究:以天山公路边坡为例[D].成都:成都理工大学,2012.Huang Yong.Research on Freeze-thaw Mechanical Behavior of Rock Mass and Collapse Formation Mechanism along the HighwayLocated in Alpine and Strong Earthquake Regions:Taking Side Slope of Tianshan Highway as an Example[D].Chengdu:Chengdu University of Technology,2012.
[4]Zhang S J,Lai Y M,Zhang X F,et al.Study on the damage propagation of surrounding rock from a cold-region tunnel under freezethaw cycle condition[J].Tunnelling&Underground Space Technology Incorporating Trenchless Technology Research,2004,19(3):295-302.
[5]张慧梅,杨更社.岩石冻融力学实验及损伤扩展特性[J].中国矿业大学学报,2011,40(1):140-145.Zhang Huimei,Yang Gengshe.Freeze-thaw cycling and mechanical experiment anddamage propagation characteristics of rock[J].Journal of China University of Mining&Technology,2011,40(1):140-145.
[6]徐光苗,刘泉声.岩石冻融破坏机理分析及冻融力学试验研究[J].岩石力学与工程学报,2005,24(17):3076-3082.Xu Guangmiao,Liu Quansheng.Analysis of mechanism of rock failure due to freeze-thaw cycling and mechanical testing study on frozen-thawed rocks[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(17):3076-3082.
[7]贾海梁.多孔岩石及裂隙岩体冻融损伤机制的理论模型和试验研究[D].武汉:中国地质大学(武汉),2016.Jia Hailiang.Theoretical Damage Models of Porous Rocks and Hard Jointed Rocks Subjected to Frost Action and Further ExperimentalVerifications[D].Wuhan:China University of Geosciences(Wuhan),2016.
[8]裴向军,蒙明辉,袁进科,等.干燥及饱水状态下裂隙岩石冻融特征研究[J].岩土力学,2017,38(7):1999-2006.Pei Xiangjun,Meng Minghui,Yuan Jinke,et al.Freezing-thawing characteristics of fractured rockmass under dry and saturated conditions[J].Rock and Soil Mechanics,2017,38(7):1999-2006.
[9]刘泉声,黄诗冰,康永水,等.裂隙岩体冻融损伤研究进展与思考[J].岩石力学与工程学报,2015,34(3):452-471.Liu Quansheng,Huang Shibing,Kang Yongshui,et al.Advance and review on freezing-thawing damage of fractured rock[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(3):452-471.
[10]申艳军,杨更社,荣腾龙,等.冻融循环作用下单裂隙类砂岩局部化损伤效应及端部断裂特性分析[J].岩石力学与工程学报,2017,36(3):562-570.ShenYanjun,Yang Gengshe,Rong Tenglong,et al.Localized damage effects of quasi-sandstone with single fracture and fracture behaviors of joint end under cyclic freezing and thawing[J].Chinese Journal of Rock Mechanics and Engineering,2017,36(3):562-570.
[11]李庆芬.断裂力学及其工程应用[M].哈尔滨:哈尔滨工程大学出版社,1998.Li Qingfen.Fracture Mechanics and Engineering Application[M].Harbin:Harbin Engeering University Press,1998.