砂质泥岩三轴卸荷流变力学特性试验研究
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摘要
流变对工程岩体的长期变形稳定具有十分重要的影响,但目前关于卸荷流变的试验研究中通常只考虑恒轴压卸围压的应力路径,与隧洞开挖过程中围岩的应力调整过程存在一定的差距。以砂质泥岩为试验研究对象,设计进行了加轴压卸围压和恒轴压卸围压条件下的分级卸荷流变试验。试验结果表明:恒轴压卸围压和加轴压卸围压方案下岩样的流变变形趋势总体一致,但相同初始围压条件下,加轴压卸围压试样破坏的围压相对较高,偏应力相对较大,但长期强度与破坏应力的比值相对较小;在围压卸载至岩样临近破坏时,加轴压卸围压方案下岩样的流变应变增长速率明显较快,试样破坏的更加突然;恒轴压卸围压条件下岩样的破坏形态相对简单,一般只存在一条完整的剪切破坏面,而加轴压卸围压条件下岩样的破坏形态要复杂得多,除了控制性的剪切破坏面之外,还伴随有一定数量的次生剪裂纹和张拉裂纹,而且初始围压越大,试样的次生裂纹越多。因此,在隧洞围岩长期变形稳定分析过程中,单纯的恒轴压卸围压流变试验不能满足工程实际需求,应该尽量丰富岩石力学试验的应力路径,以便较好地模拟工程岩体应力的实际变化过程,研究成果为隧洞围岩的长期变形稳定性研究提供了较好的研究思路。
Rheology has extremely significant influence on the long-term deformation and stability of engineering rock mass. Current experimental research on unloading rheology only considers the stress path under unloading confining pressure with the constant axial stress, however it is different from the process of stress adjustment in surrounding rock during tunnel excavating. Stepwise unloading rheological tests are conducted on sandy mudstone samples which are under unloading confining pressure with the axial compression or with the constant axial stress. The results show that the rheological deformation trends of rock samples under both unloading confining pressure are generally consistent. At the same initial confining pressure, the failure confining pressure under axial compression and the deviatoric stress are relatively higher than that under constant axial stress, but the ratio of long-term strength to failure stress is opposite. When the confining pressure unloads reach up to the point where the rock sample approaches failure, the growth rate of rheological strain under axial compression obviously becomes faster than that under constant axial stress, and the failure occurs more suddenly. The failure modes of rock samples under constant axial stress usually appear as one complete shear failure plane. By contrast, the failure modes of rock samples under axial compression are more complicated with a certain amount of secondary shear cracks and tension cracks, in addition to the controlled shear failure plane. Moreover, the secondary cracks increase with the increase of initial confining pressure. Therefore, the unloading confining pressure with the constant axial stress seems difficultly satisfy the requirement of engineering projects undergone a long-term deformation and stability of surrounding rock. The stress paths of tests should be conducted in more detail to simulate the actual stress change process of engineering rock mass. The results provide insights into the research on long-term deformation and stability of underground surrounding rock.
Rheology has extremely significant influence on the long-term deformation and stability of engineering rock mass. Current experimental research on unloading rheology only considers the stress path under unloading confining pressure with the constant axial stress, however it is different from the process of stress adjustment in surrounding rock during tunnel excavating. Stepwise unloading rheological tests are conducted on sandy mudstone samples which are under unloading confining pressure with the axial compression or with the constant axial stress. The results show that the rheological deformation trends of rock samples under both unloading confining pressure are generally consistent. At the same initial confining pressure, the failure confining pressure under axial compression and the deviatoric stress are relatively higher than that under constant axial stress, but the ratio of long-term strength to failure stress is opposite. When the confining pressure unloads reach up to the point where the rock sample approaches failure, the growth rate of rheological strain under axial compression obviously becomes faster than that under constant axial stress, and the failure occurs more suddenly. The failure modes of rock samples under constant axial stress usually appear as one complete shear failure plane. By contrast, the failure modes of rock samples under axial compression are more complicated with a certain amount of secondary shear cracks and tension cracks, in addition to the controlled shear failure plane. Moreover, the secondary cracks increase with the increase of initial confining pressure. Therefore, the unloading confining pressure with the constant axial stress seems difficultly satisfy the requirement of engineering projects undergone a long-term deformation and stability of surrounding rock. The stress paths of tests should be conducted in more detail to simulate the actual stress change process of engineering rock mass. The results provide insights into the research on long-term deformation and stability of underground surrounding rock.
引文
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[8]赵延林,曹平,陈沅江,等.分级加卸载下节理软岩流变试验及模型[J].煤炭学报,2008,33(7):748-753.ZHAO Yan-lin,CAO Ping,CHEN Yuan-jiang,et al.Creep properties experiment and model of jointed soft rocks under step load and unload[J].Journal of China Coal Society,2008,33(7):748-753.
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[11]朱定华.南京红层软岩流变特性试验研究[J].南京工业大学学报,2002,24(5):77-79.ZHU Ding-hua.Experimental study of Nangjing red-bed on rheology[J].Journal of Nanjing University of Technology,2002,24(5):77-79.
[12]徐卫亚,杨圣奇,褚卫江.岩石非线性黏弹塑性流变模型(河海模型)及其工程应用[J].岩石力学与工程学报,2006,25(3):433-447.XU Wei-ya,YANG Sheng-qi,CHU Wei-jiang.Nonlinear viscoelasto-plastic rheological model(Hohai model)of rock and its engineering application[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(3):433-447.
[13]赵延林,曹平,文有道,等.岩石弹黏塑性流变试验和非线性流变模型研究[J].岩石力学与工程学报,2008,27(3):477-486.ZHAO Yan-lin,CAO Ping,WEN You-dao,et al.Elastovisco-plastic rheological experiment and nonlinear rheological model of rocks[J].Chinese Journal of Rock Mechanics and Engineering,2008,27(3):477-486.
[14]夏才初,闫子舰,王晓东,等.大理岩卸荷条件下弹黏塑性本构关系研究[J].岩石力学与工程学报,2009,28(3):459-466.XIA Cai-chu,YAN Zi-jian,WANG Xiao-dong,et al.Research on elasto-viscoplastic constitutive relation of marble under unloading condition[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(3):459-466.
[15]朱杰兵,汪斌,杨火平,等.页岩卸荷流变力学特性的试验研究[J].岩石力学与工程学报,2007,26(增刊2):4552-4556.ZHU Jie-bing,WANG Bin,YANG Huo-ping,et al.Experimental study on rheological mechanical properties of shale under unloading condition[J].Chinese Journal of Rock Mechanics and Engineering,2007,26(Supp.2):4552-4556.
[16]王宇,李建林,邓华锋,等.软岩三轴卸荷流变力学特性及本构模型研究[J].岩土力学,2012,33(11):3338-3344.WANG Yu,LI Jian-lin,DENG Huan-feng,et al.Investigation on unloading triaxial rheological mechanical properties of soft rock and its constitutive model[J].Rock and Soil Mechanics,2012,33(11):3338-3344.
[17]王宇,李建林,左亚,等.不同卸荷路径下贯通裂隙岩体流变试验研究[J].岩石力学与工程学报,2015,34(增1):2900-2908.WANG Yu,LI Jian-lin,ZUO Ya,et al.Rheological experimental study of consecutive fractured rock mass under different unloading conditions[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(Supp.1):2900-2908.
[18]长江水利委员会长江科学院.SL264-2001水利水电工程岩石试验规程[S].北京:中国水利水电出版社,2001.Changjiang River Scientific Research Institute of Changjiang Water Resources Commission.SL264-2001Specifications for rock tests in water conservancy and hydroelectric engineering[S].Beijing:China Water Power Press,2001.
[19]邓华锋,李建林,邓成进,等.岩石力学试验中岩样选择和抗压强度预测方法研究[J].岩土力学,2011,32(11):3399-3403.DENG Hua-feng,LI Jian-lin,DENG Cheng-jin,et al.Analysis of sampling in rock mechanics test and compressive strength prediction methods[J].Rock and Soil Mechanics,2011,32(11):3399-3403.
[20]纪文栋,杨春和,姚院峰,等.应变加载速率对盐岩力学性能的影响[J].岩石力学与工程学报,2011,30(12):2507-2513.JI Wen-dong,YANG Chun-he,YAO Yuan-feng,et al.The effect of loading rate on the mechanical properties of salt rock[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(12):2507-2513.
[21]邓华锋,原先凡,李建林,等.软岩三轴加-卸载试验的破坏特征及抗压强度取值方法研究[J].岩土力学,2014,35(4):959-964.DENG Hua-feng,YUAN Xian-fan,LI Jian-lin,et al.Research on failure characteristics and determination method for compressive strength of soft rock in triaxial loading and unloading tests[J].Rock and Soil Mechanics,2014,35(4):959-964.
[2]李建林.卸荷岩体力学理论与应用[M].北京:中国建筑工业出版社,1999.LI Jian-lin.The theory and application of unloading rock mass mechanics[M].Beijing:China Architecture&Building Press,1999.
[3]BOUKHAROVG G N,CHANDA M W,BOUKHAROV N G.The three processes of brittle crystalline rock creep[J].International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts,1995,32(4):325-335.
[4]MARANINIE,BRIGNOLI M.Creep behavior of a weak rock:Experimental characterization[J].International Journal of Rock Mechanics and Mining Sciences,1999,36(1):127-138.
[5]YANG Chun-he,DAEMEN J J K,YIN Jian-hua.Experimental investigation of creep behavior of salt rock[J].International Journal of Rock Mechanics and Mining Sciences,1999,36(3):233-242.
[6]胡政,刘佑荣,武尚,等.高地应力区砂岩在卸荷条件下的变形参数劣化试验研究[J].岩土力学,2014,35(增刊1):78-84.HU Zheng,LIU You-rong,WU Shang,et al.Experimental study of deformation parameters degradation of sandstone in high geostress regions under unloading conditions[J].Rock and Soil Mechanics,2014,35(Supp.1):78-84.
[7]杨春和,白世伟.应力水平及加载路径对盐岩时效的影响[J].岩石力学与工程学报,2000,19(3):270-275.YANG Chun-he,BAI Shi-wei.Stress level and loading path effect on time dependent properties of salt rock[J].Chinese Journal of Rock Mechanics and Engineering,2000,19(3):270-275.
[8]赵延林,曹平,陈沅江,等.分级加卸载下节理软岩流变试验及模型[J].煤炭学报,2008,33(7):748-753.ZHAO Yan-lin,CAO Ping,CHEN Yuan-jiang,et al.Creep properties experiment and model of jointed soft rocks under step load and unload[J].Journal of China Coal Society,2008,33(7):748-753.
[9]熊良宵,杨林德,张尧,等.锦屏二级水电站绿片岩双轴压缩蠕变特性试验研究[J].岩石力学与工程学报,2008,27(增刊2):3928-3934.XIONG Liang-xiao,YANG Lin-de,ZHANG Yao,et al.Experimental study on creep behaviors of greenschist specimen from JinpingⅡhydropower station under biaxial compression[J].Chinese Journal of Rock Mechanics and Engineering,2008,27(Supp.2):3928-3934.
[10]杨文东,张强勇,陈芳,等.大岗山水电站坝区辉绿岩流变特性的三轴试验研究[J].四川大学学报(工程科学版),2011,43(5):64-70,101.YANG Wen-dong,ZHANG Qiang-yong,CHEN Fang,et al.Triaxial test research into rheological properties of diabase in Dagangshan Hydropower Station Dams site[J].Journal of Sichuan University(Engineering Science Edition),2011,43(5):64-70,101.
[11]朱定华.南京红层软岩流变特性试验研究[J].南京工业大学学报,2002,24(5):77-79.ZHU Ding-hua.Experimental study of Nangjing red-bed on rheology[J].Journal of Nanjing University of Technology,2002,24(5):77-79.
[12]徐卫亚,杨圣奇,褚卫江.岩石非线性黏弹塑性流变模型(河海模型)及其工程应用[J].岩石力学与工程学报,2006,25(3):433-447.XU Wei-ya,YANG Sheng-qi,CHU Wei-jiang.Nonlinear viscoelasto-plastic rheological model(Hohai model)of rock and its engineering application[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(3):433-447.
[13]赵延林,曹平,文有道,等.岩石弹黏塑性流变试验和非线性流变模型研究[J].岩石力学与工程学报,2008,27(3):477-486.ZHAO Yan-lin,CAO Ping,WEN You-dao,et al.Elastovisco-plastic rheological experiment and nonlinear rheological model of rocks[J].Chinese Journal of Rock Mechanics and Engineering,2008,27(3):477-486.
[14]夏才初,闫子舰,王晓东,等.大理岩卸荷条件下弹黏塑性本构关系研究[J].岩石力学与工程学报,2009,28(3):459-466.XIA Cai-chu,YAN Zi-jian,WANG Xiao-dong,et al.Research on elasto-viscoplastic constitutive relation of marble under unloading condition[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(3):459-466.
[15]朱杰兵,汪斌,杨火平,等.页岩卸荷流变力学特性的试验研究[J].岩石力学与工程学报,2007,26(增刊2):4552-4556.ZHU Jie-bing,WANG Bin,YANG Huo-ping,et al.Experimental study on rheological mechanical properties of shale under unloading condition[J].Chinese Journal of Rock Mechanics and Engineering,2007,26(Supp.2):4552-4556.
[16]王宇,李建林,邓华锋,等.软岩三轴卸荷流变力学特性及本构模型研究[J].岩土力学,2012,33(11):3338-3344.WANG Yu,LI Jian-lin,DENG Huan-feng,et al.Investigation on unloading triaxial rheological mechanical properties of soft rock and its constitutive model[J].Rock and Soil Mechanics,2012,33(11):3338-3344.
[17]王宇,李建林,左亚,等.不同卸荷路径下贯通裂隙岩体流变试验研究[J].岩石力学与工程学报,2015,34(增1):2900-2908.WANG Yu,LI Jian-lin,ZUO Ya,et al.Rheological experimental study of consecutive fractured rock mass under different unloading conditions[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(Supp.1):2900-2908.
[18]长江水利委员会长江科学院.SL264-2001水利水电工程岩石试验规程[S].北京:中国水利水电出版社,2001.Changjiang River Scientific Research Institute of Changjiang Water Resources Commission.SL264-2001Specifications for rock tests in water conservancy and hydroelectric engineering[S].Beijing:China Water Power Press,2001.
[19]邓华锋,李建林,邓成进,等.岩石力学试验中岩样选择和抗压强度预测方法研究[J].岩土力学,2011,32(11):3399-3403.DENG Hua-feng,LI Jian-lin,DENG Cheng-jin,et al.Analysis of sampling in rock mechanics test and compressive strength prediction methods[J].Rock and Soil Mechanics,2011,32(11):3399-3403.
[20]纪文栋,杨春和,姚院峰,等.应变加载速率对盐岩力学性能的影响[J].岩石力学与工程学报,2011,30(12):2507-2513.JI Wen-dong,YANG Chun-he,YAO Yuan-feng,et al.The effect of loading rate on the mechanical properties of salt rock[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(12):2507-2513.
[21]邓华锋,原先凡,李建林,等.软岩三轴加-卸载试验的破坏特征及抗压强度取值方法研究[J].岩土力学,2014,35(4):959-964.DENG Hua-feng,YUAN Xian-fan,LI Jian-lin,et al.Research on failure characteristics and determination method for compressive strength of soft rock in triaxial loading and unloading tests[J].Rock and Soil Mechanics,2014,35(4):959-964.
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