含水率对红砂岩瞬时和蠕变力学性质影响的试验研究
|
摘要
水是影响岩体工程稳定性的重要因素。为了全面分析水对岩石瞬时及蠕变力学特性的影响,设计了两类试验:单轴压缩强度试验和蠕变试验。通过吸水试验分析红砂岩的吸水特征,并以此为依据制备不同含水率的标准试件。首先对9组不同含水率的试件进行单轴压缩强度试验。利用体积应变法和LSR法(Lateral Strain Response)确定红砂岩在单轴压缩条件下的4个特征应力:闭合应力、启裂应力、损伤应力和破坏应力,从而得到了含水率与红砂岩力学参数的定量关系。结果表明,应力应变曲线上各阶段特征应力随含水率增大而服从负指数规律衰减,并且当试件达到饱和后,各特征应力趋于稳定。由于高孔隙率的特性,导致红砂岩的特征应力在短时间内显著降低。启裂应力σi与闭合应力σc之差随着含水率的增加而减小。这说明水的增加导致红砂岩非线性特征增强。强度和弹性模量损失系数随含水率呈指数函数增长的趋势,饱和红砂岩的强度和弹模总损失系数分别是0. 484和0. 334。此外,将5组不同初始含水率的试件持续浸在充满水的环境试验箱中,开展荷载与水共同作用下的蠕变试验,从而得到长期水环境对红砂岩蠕变力学特征的影响。结果表明,试件的瞬时应变和稳态应变率随含水率增加呈指数形式增大,蠕变应变和破坏时间随含水率增加而减小。当含水率趋于稳定时,红砂岩的蠕变特性仍然有显著的变化,其原因在于环境中的水沿蠕变新生成的裂缝进一步运移到裂缝尖端,初始裂纹进一步扩展。实验结果不仅强调了短时间内水对高孔隙率岩石瞬时力学性质的急剧弱化作用,而且强调了环境中的水对饱和岩石蠕变力学性质的持续影响作用。此外,实验数据和拟合方程将为岩体工程长期稳定性的评估提供一定的参考价值。
Water is an important factor affecting the stability of rock mass engineering.In order to comprehensively analyze the influence of water on the instantaneous and creep mechanical properties of rock,two kinds of tests were designed: uniaxial compression strength test and creep test.The water absorption characteristics of red sandstone were analyzed by water absorption experiments. Based on this,the standard samples with different water contents were prepared.First,the uniaxial compression strength tests were carried out on nine groups of specimens with different water contents.The volume strain method and LSR( Lateral Strain Response) method were used to determine the four characteristic stresses of red sandstone under uniaxial compression: closure stress,crack initiation stress,damage stress and failure stress,thus,the quantitative relationship between water content and mechanical parameters of red sandstone was obtained.Results show that the characteristic stress of each stage on the stress-strain curve decreases in negative exponential form with the increase of water content.When the specimen reaches saturation,the characteristic stress tends to be stable.Due to the characteristics of high porosity,the characteristic stress of red sandstone decrease significantly in a short time.The difference between crack initiation stress σiand closure stress σcdecreases with the increase of water content.This indicates that the increase of water leads to the enhancement of the nonlinear characteristics of red sandstone.The loss coefficient of strength and elastic modulus increases exponentially with water content,and the total loss coefficient of strength and elastic modulus of saturated red sandstone are 0. 484 and 0. 334,respectively. In addition,five groups of specimens with different initial water contents were continuously immersed in an environmental chamber filled with water to conduct creep tests under the combined action of load and water,so as to obtain the influence of long-term water environment on the creep mechanical characteristics of red sandstone.Results show that the instantaneous strain and steady-state strain rate of red sandstone increase exponentially with the increase of water content,whereas the time-dependent strain and time to failure decrease with the increase of water content.When the water content tends to be stable,the creep behavior of red sandstone still changes significantly. The reason is that water in the environment is further migrated to the crack tip along the new cracks generated by creep,and the initial crack expands further.The experimental results emphasize not only the great water weakening effect on the instantaneous mechanical properties of high porosity rocks in a short period of time,but also the sustained effect of water on the creep mechanics properties of saturated rock under the combined action of load and water.In addition,the experimental data and fitted equation will provide a reference for the long-term stability assessment of rock mass engineering.
Water is an important factor affecting the stability of rock mass engineering.In order to comprehensively analyze the influence of water on the instantaneous and creep mechanical properties of rock,two kinds of tests were designed: uniaxial compression strength test and creep test.The water absorption characteristics of red sandstone were analyzed by water absorption experiments. Based on this,the standard samples with different water contents were prepared.First,the uniaxial compression strength tests were carried out on nine groups of specimens with different water contents.The volume strain method and LSR( Lateral Strain Response) method were used to determine the four characteristic stresses of red sandstone under uniaxial compression: closure stress,crack initiation stress,damage stress and failure stress,thus,the quantitative relationship between water content and mechanical parameters of red sandstone was obtained.Results show that the characteristic stress of each stage on the stress-strain curve decreases in negative exponential form with the increase of water content.When the specimen reaches saturation,the characteristic stress tends to be stable.Due to the characteristics of high porosity,the characteristic stress of red sandstone decrease significantly in a short time.The difference between crack initiation stress σiand closure stress σcdecreases with the increase of water content.This indicates that the increase of water leads to the enhancement of the nonlinear characteristics of red sandstone.The loss coefficient of strength and elastic modulus increases exponentially with water content,and the total loss coefficient of strength and elastic modulus of saturated red sandstone are 0. 484 and 0. 334,respectively. In addition,five groups of specimens with different initial water contents were continuously immersed in an environmental chamber filled with water to conduct creep tests under the combined action of load and water,so as to obtain the influence of long-term water environment on the creep mechanical characteristics of red sandstone.Results show that the instantaneous strain and steady-state strain rate of red sandstone increase exponentially with the increase of water content,whereas the time-dependent strain and time to failure decrease with the increase of water content.When the water content tends to be stable,the creep behavior of red sandstone still changes significantly. The reason is that water in the environment is further migrated to the crack tip along the new cracks generated by creep,and the initial crack expands further.The experimental results emphasize not only the great water weakening effect on the instantaneous mechanical properties of high porosity rocks in a short period of time,but also the sustained effect of water on the creep mechanics properties of saturated rock under the combined action of load and water.In addition,the experimental data and fitted equation will provide a reference for the long-term stability assessment of rock mass engineering.
引文
[1] HAWKINS A B,MCCONNELL B J.Sensitivity of sandstone strength and deformability to changes in moisture content[J].Quarterly Journal of Engineering Geology&Hydrogeology,1992,25(2):115-130.
[2]周翠英,邓毅梅,谭祥韶,等.饱水软岩力学性质软化的试验研究与应用[J].岩石力学与工程学报,2005,24(1):33-38.ZHOU Cuiying,DENG Yimei,TAN Xiangshao,et al. Experimental research on the softening of mechanical properties of saturated soft rocks and application[J]. Chinese Journal of Rock Mechanics and Engineering,2005,24(1):33-38.
[3]段宏飞,姜振泉,朱术云,等.深部矿井岩石水稳性微观机理及强度软化特性研究[J].岩土工程学报,2012,34(9):1636-1645.DUAN Hongfei,JIANG Zhenquan,ZHU Shuyun,et al.Micro-mechanism of water stability and characteristics of strength softening of rock in deep mines[J]. Chinese Journal of Geotechnical Engineering,2012,34(9):1636-1645.
[4]邓华锋,原先凡,李建林,等.饱水度对砂岩纵波波速及强度影响的试验研究[J].岩石力学与工程学报,2013,32(8):1625-1631.DENG Huafeng,YUAN Xianfan,LI Jianlin,et al. Experimental research on influence of saturation degree on sandstone longitudinal wave velocity and strength[J]. Chinese Journal of Rock Mechanics and Engineering,2013,32(8):1625-1631.
[5]蒋长宝,段敏克,尹光志,等.不同含水状态下含瓦斯原煤加卸载试验研究[J].煤炭学报,2016,41(9):2230-2237.JIANG Changbao,DUAN Minke,YIN Guangzhi,et al. Loading-unloading experiments of coal containing gas under the condition of different moisture contents[J]. Journal of China Coal Society,2016,41(9):2230-2237.
[6] ZHANG D,GAMAGE R P,PERERA M,et al.Influence of water saturation on the mechanical behaviour of low-permeability reservoir rocks[J].Energies,2017,10(2):236.
[7] YAO Q,CHEN T,JU M,et al.Effects of water intrusion on mechanical properties of and crack propagation in coal[J]. Rock Mechanics&Rock Engineering,2016,49(12):1-11.
[8]唐鸥玲,李天斌,陈国庆.含水率对砂岩渐进破裂过程影响的试验研究[J].实验力学,2016,31(4):503-510.TANG Ouling,LI Tianbin,CHEN Guoqing.Experimental study of the effect of moisture content on progressive failure process of sandstone[J].Journal of Experimental Mechanics,2016,31(4):503-510.
[9] LAJTAI E Z,SCHMIDTKE R H,BIELUS L P.The effect of water on the time-dependent deformation and fracture of a granite[J].International Journal of Rock Mechanics&Mining Sciences&Geomechanics Abstracts,1987,24(4):247-255.
[10] KRANZ R L.Crack growth and development during creep of Barre granite[J].International Journal of Rock Mechanics&Mining Sciences&Geomechanics Abstracts,1979,16(1):23-35.
[11]朱合华,叶斌.饱水状态下隧道围岩蠕变力学性质的试验研究[J].岩石力学与工程学报,2002,21(12):1791-1796.ZHU Hehua,YE Bin. Experimental study of mechanical properties of rock creep in saturation[J].Chinese Journal of Rock Mechanics and Engineering,2002,21(12):1791-1796.
[12]巨能攀,黄海峰,郑达,等.考虑含水率的红层泥岩蠕变特性及改进伯格斯模型[J].岩土力学,2016,37(S2):67-74.JU Nengpan,HUANG Haifeng,ZHENG Da,et al. Improved Burgers model for creep characteristics of red bed mudstone considering water content[J]. Rock and Soil Mechanics,2016,37(S2):67-74.
[13] ZHOU Z,CAI X,CAO W,et al.Influence of water content on mechanical properties of rock in both saturation and drying processes[J].Rock Mechanics and Rock Engineering,2016,49(8):3009-3025.
[14] TANG S.The effects of water on the strength of black sandstone in a brittle regime[J].Engineering Geology,2018,239:167-178.
[15] NICKSIAR M,MARTIN C D. Evaluation of methods for determining crack initiation in compression tests on low-porosity rocks[J].Rock Mechanics and Rock Engineering,2012,45(4):607-617.
[16] LI P F,CAI Q C.Analysis of the approaches to determine crack initiation stress of rock materials in compression tests[J].Applied Mechanics&Materials,2014,556-562:2857-2861.
[2]周翠英,邓毅梅,谭祥韶,等.饱水软岩力学性质软化的试验研究与应用[J].岩石力学与工程学报,2005,24(1):33-38.ZHOU Cuiying,DENG Yimei,TAN Xiangshao,et al. Experimental research on the softening of mechanical properties of saturated soft rocks and application[J]. Chinese Journal of Rock Mechanics and Engineering,2005,24(1):33-38.
[3]段宏飞,姜振泉,朱术云,等.深部矿井岩石水稳性微观机理及强度软化特性研究[J].岩土工程学报,2012,34(9):1636-1645.DUAN Hongfei,JIANG Zhenquan,ZHU Shuyun,et al.Micro-mechanism of water stability and characteristics of strength softening of rock in deep mines[J]. Chinese Journal of Geotechnical Engineering,2012,34(9):1636-1645.
[4]邓华锋,原先凡,李建林,等.饱水度对砂岩纵波波速及强度影响的试验研究[J].岩石力学与工程学报,2013,32(8):1625-1631.DENG Huafeng,YUAN Xianfan,LI Jianlin,et al. Experimental research on influence of saturation degree on sandstone longitudinal wave velocity and strength[J]. Chinese Journal of Rock Mechanics and Engineering,2013,32(8):1625-1631.
[5]蒋长宝,段敏克,尹光志,等.不同含水状态下含瓦斯原煤加卸载试验研究[J].煤炭学报,2016,41(9):2230-2237.JIANG Changbao,DUAN Minke,YIN Guangzhi,et al. Loading-unloading experiments of coal containing gas under the condition of different moisture contents[J]. Journal of China Coal Society,2016,41(9):2230-2237.
[6] ZHANG D,GAMAGE R P,PERERA M,et al.Influence of water saturation on the mechanical behaviour of low-permeability reservoir rocks[J].Energies,2017,10(2):236.
[7] YAO Q,CHEN T,JU M,et al.Effects of water intrusion on mechanical properties of and crack propagation in coal[J]. Rock Mechanics&Rock Engineering,2016,49(12):1-11.
[8]唐鸥玲,李天斌,陈国庆.含水率对砂岩渐进破裂过程影响的试验研究[J].实验力学,2016,31(4):503-510.TANG Ouling,LI Tianbin,CHEN Guoqing.Experimental study of the effect of moisture content on progressive failure process of sandstone[J].Journal of Experimental Mechanics,2016,31(4):503-510.
[9] LAJTAI E Z,SCHMIDTKE R H,BIELUS L P.The effect of water on the time-dependent deformation and fracture of a granite[J].International Journal of Rock Mechanics&Mining Sciences&Geomechanics Abstracts,1987,24(4):247-255.
[10] KRANZ R L.Crack growth and development during creep of Barre granite[J].International Journal of Rock Mechanics&Mining Sciences&Geomechanics Abstracts,1979,16(1):23-35.
[11]朱合华,叶斌.饱水状态下隧道围岩蠕变力学性质的试验研究[J].岩石力学与工程学报,2002,21(12):1791-1796.ZHU Hehua,YE Bin. Experimental study of mechanical properties of rock creep in saturation[J].Chinese Journal of Rock Mechanics and Engineering,2002,21(12):1791-1796.
[12]巨能攀,黄海峰,郑达,等.考虑含水率的红层泥岩蠕变特性及改进伯格斯模型[J].岩土力学,2016,37(S2):67-74.JU Nengpan,HUANG Haifeng,ZHENG Da,et al. Improved Burgers model for creep characteristics of red bed mudstone considering water content[J]. Rock and Soil Mechanics,2016,37(S2):67-74.
[13] ZHOU Z,CAI X,CAO W,et al.Influence of water content on mechanical properties of rock in both saturation and drying processes[J].Rock Mechanics and Rock Engineering,2016,49(8):3009-3025.
[14] TANG S.The effects of water on the strength of black sandstone in a brittle regime[J].Engineering Geology,2018,239:167-178.
[15] NICKSIAR M,MARTIN C D. Evaluation of methods for determining crack initiation in compression tests on low-porosity rocks[J].Rock Mechanics and Rock Engineering,2012,45(4):607-617.
[16] LI P F,CAI Q C.Analysis of the approaches to determine crack initiation stress of rock materials in compression tests[J].Applied Mechanics&Materials,2014,556-562:2857-2861.
© 2004-2018 中国地质图书馆版权所有 京ICP备05064691号 京公网安备11010802017129号 地址：北京市海淀区学院路29号 邮编：100083 电话：办公室：(+86 10)66554848；文献借阅、咨询服务、科技查新：66554700 |