加载途径对深部孔隙性砂岩力学特性的影响
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摘要
深部孔隙性砂岩具有压实程度高、岩石较致密、孔隙度较低、且孔隙中一般含有油/气或水、孔隙流体具有压力的特点。已有的理论研究表明,多孔介质孔隙流体压力对岩石的变形和破坏存在一定影响,不同岩石其影响程度不同。从孔隙流体压力为正常静水压力、实际地层孔隙压力和大气压3个方面,通过实验研究由于孔隙内压改变而引起的加载途径变化对岩石变形和破坏的影响。研究结果表明:孔隙流体压力的存在使岩石的塑性增强,即模拟砂岩实际地层孔隙压力和围压得到的三轴抗压强度、轴向应变、径向应变和泊松比大于其他两个条件下相应的值,弹性模量则小于其他两个条件下的岩石弹性模量;对深部孔隙性地层岩石,要表述岩石的力学特性,应考虑孔隙压力的存在和影响,应尽量模拟岩石在深部埋藏条件下所受到的实际上覆岩石压力、实际地层孔隙压力测试岩石的应力–应变特性。
The deep porous sandstone has many unique features,such as high consolidation level,high compactability,lower porosity,oil/gas/water-included pore,pore fluid with pressure holding and so on.The existing studies have shown that the pore fluid pressure of porous media has some effects on the deformation and damage of rock,and the influential level is distinct to different rock masses.Based on the pore fluid pressure which is composed of regular hydrostatic pressure,actual formation pore pressure and atmospheric pressure,the experimental study has been carried out to analyze the effect of different loading paths owing to the change of internal pore pressure on the deformation and damage of rock samples.The results have shown that the existence of pore fluid pressure enhances the plasticity of rock sample.This means that the triaxial compressive strength,the axial strain,the radial strain;and the Poisson′s ratio obtained by simulating the actual pore pressure and confining pressure are greater than those obtained under the other two conditions,while the elastic modulus is less than that obtained under the other two conditions.In order to declare the mechanical behavior of the deep porous sandstone,the existence and influence of pore fluid pressure should be considered.If possible,the actual overlying pressure of deep embedded rock and the actual formation pore pressure should be simulated to test the stress-strain characters of rock samples.
The deep porous sandstone has many unique features,such as high consolidation level,high compactability,lower porosity,oil/gas/water-included pore,pore fluid with pressure holding and so on.The existing studies have shown that the pore fluid pressure of porous media has some effects on the deformation and damage of rock,and the influential level is distinct to different rock masses.Based on the pore fluid pressure which is composed of regular hydrostatic pressure,actual formation pore pressure and atmospheric pressure,the experimental study has been carried out to analyze the effect of different loading paths owing to the change of internal pore pressure on the deformation and damage of rock samples.The results have shown that the existence of pore fluid pressure enhances the plasticity of rock sample.This means that the triaxial compressive strength,the axial strain,the radial strain;and the Poisson′s ratio obtained by simulating the actual pore pressure and confining pressure are greater than those obtained under the other two conditions,while the elastic modulus is less than that obtained under the other two conditions.In order to declare the mechanical behavior of the deep porous sandstone,the existence and influence of pore fluid pressure should be considered.If possible,the actual overlying pressure of deep embedded rock and the actual formation pore pressure should be simulated to test the stress-strain characters of rock samples.
引文
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[8]刘恩龙,沈珠江.不同应力路径下结构性土的力学特性[J].岩石力学与工程学报,2006,25(10):2 058–2 064.(LIU Enlong,SHEN Zhujiang.Mechanical behavior of structured soils under different stress paths[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(10):2 058–2 064.(in Chinese))
[9]沈明荣,石振明,张雷.不同加载路径对岩石变形特性的影响[J].岩石力学与工程学报,2003,22(8):1 234–1 238.(SHEN Mingrong,SHI Zhenming,ZHANG Lei.Deformation properties of rock samples under different loading paths[J].Chinese Journal of Rock Mechanics and Engineering,2003,22(8):1 234–1 238.(in Chinese))
[10]尤明庆.复杂路径下岩样的强度和变形特性[J].岩石力学与工程学报,2002,21(1):23–28.(YOU Mingqing.Strengh and deformation of rock under complex loading path[J].Chinese Journal of Rock Mechanics and Engineering,2002,21(1):23–28.(in Chinese))
[11]李永明,郝临山,魏胜利,等.煤岩加卸载不同应力途径变形破坏力学参数的研究[J].煤炭技术,2006,25(12):129–131.(LI Yongming,HAO Linshan,WEI Shengli,et al.Research on coal deformation and failure mechanical parameters in different stress paths of loading and unloading test[J].Coal Technology,2006,25(12):129–131.(in Chinese))
[12]孟召平,李明生,陆鹏庆,等.深部温度、压力条件及其对砂岩力学性质的影响[J].岩石力学与工程学报,2006,25(6):1 177–1 181.(MENG Zhaoping,LI Mingsheng,LU Pengqing,et al.Temperature and pressure under deep conditions and their influences on mechanical properties of sandstone[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(6):1 177–1 181.(in Chinese))
[2]耿乃光,许东俊.应力途径对砂岩力学性质的影响[J].地球物理学报,1983,26(4):401–404.(GENG Naiguang,XU Dongjun.The effect of stress path on properties of sandstone[J].Chinese Journal of Geophysics,1983,26(4):401–404.(in Chinese))
[3]姚孝新,耿乃光,陈颙.应力途径对岩石脆性–延性变化的影响[J].地球物理学报,1980,23(3):312–319.(YAO Xiaoxin,GENG Naiguang,CHEN Yu.The effect of stress path on brittleness and ductility of rocks[J].Chinese Journal of Geophysics,1980,23(3):312–319.(in Chinese))
[4]陈颙,姚孝新,耿乃光.应力途径、岩石的强度和体积膨胀[J].中国科学(A辑:数学),1979,11(11):1 093–1 100,1 135.(CHEN Yu,YAO Xiaoxin,GENG Naiguang.Stress path,rock strength and volume expansion[J].Science in China(Series A:Mathematics),1979,11(11):1 093–1 100,1 135.(in Chinese))
[5]尤明庆,华安增.应力路径对岩样强度和变形特性的影响[J].岩土工程学报,1998,20(5):101–104.(YOU Mingqing,HUA Anzeng.Effect of stress path on strength and deformation of rock specimens[J].Chinese Journal of Geotechnical Engineering,1998,20(5):101–104.(in Chinese))
[6]吴玉山.应力路径对凝灰岩力学特性的影响[J].岩土工程学报,1983,5(1):112–121.(WU Yushan.The effects of stress path on mechanical properties of tuff rocks[J].Chinese Journal of Geotechnical Engineering,1983,5(1):112–121.(in Chinese))
[7]耿乃光,陈颙,姚孝新.岩石强度与应力途径[J].力学学报,1981,5(5):525–527.(GENG Naiguang,CHEN Yu,YAO Xiaoxin.Stress paths and strength of rocks[J].Acta Mechanica Sinica,1981,5(5):525–527.(in Chinese))
[8]刘恩龙,沈珠江.不同应力路径下结构性土的力学特性[J].岩石力学与工程学报,2006,25(10):2 058–2 064.(LIU Enlong,SHEN Zhujiang.Mechanical behavior of structured soils under different stress paths[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(10):2 058–2 064.(in Chinese))
[9]沈明荣,石振明,张雷.不同加载路径对岩石变形特性的影响[J].岩石力学与工程学报,2003,22(8):1 234–1 238.(SHEN Mingrong,SHI Zhenming,ZHANG Lei.Deformation properties of rock samples under different loading paths[J].Chinese Journal of Rock Mechanics and Engineering,2003,22(8):1 234–1 238.(in Chinese))
[10]尤明庆.复杂路径下岩样的强度和变形特性[J].岩石力学与工程学报,2002,21(1):23–28.(YOU Mingqing.Strengh and deformation of rock under complex loading path[J].Chinese Journal of Rock Mechanics and Engineering,2002,21(1):23–28.(in Chinese))
[11]李永明,郝临山,魏胜利,等.煤岩加卸载不同应力途径变形破坏力学参数的研究[J].煤炭技术,2006,25(12):129–131.(LI Yongming,HAO Linshan,WEI Shengli,et al.Research on coal deformation and failure mechanical parameters in different stress paths of loading and unloading test[J].Coal Technology,2006,25(12):129–131.(in Chinese))
[12]孟召平,李明生,陆鹏庆,等.深部温度、压力条件及其对砂岩力学性质的影响[J].岩石力学与工程学报,2006,25(6):1 177–1 181.(MENG Zhaoping,LI Mingsheng,LU Pengqing,et al.Temperature and pressure under deep conditions and their influences on mechanical properties of sandstone[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(6):1 177–1 181.(in Chinese))
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