矿物粒径对花岗岩单轴压缩特性影响的试验与模拟研究
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摘要
高放废物深部地质处置目前受到世界各国的高度重视。花岗岩是我国高放废物地质处置工程的候选围岩,深入了解处置库花岗岩的强度及破坏特性对于处置系统的设计及性能评价具有十分重要的意义。作为矿物颗粒的集合体,花岗岩是一种由石英、长石和黑云母等矿物组成的非均质岩石,矿物粒径对其宏观力学特性影响明显。以我国高放地质处置库预选区阿拉善花岗岩为例,选取矿物粒径差异明显的似斑状花岗岩和中粒花岗岩两类岩石,采用单轴压缩试验与数值模拟相结合的方式研究了矿物粒径对岩石力学特性的影响。单轴压缩试验在MTS815岩石力学试验系统进行,数值模拟采用基于离散元的颗粒流程序PFC2D完成。数值模拟过程中,以试件表面图像为基础,采用数字图像处理技术获取岩石内部矿物组分的实际空间分布,从而建立了精确反映花岗岩内部矿物种类及其空间位置的数值模型。利用该模型对花岗岩的单轴压缩试验进行了数值模拟,并与试验结果对比,论证了模型的可靠性。试验及模拟结果表明,阿拉善花岗岩破坏形式为脆性张拉破坏,裂纹大多平行于轴压方向,数字图像数值分析方法可真实地反映材料细观结构。矿物粒径对材料力学特性的影响主要表现为:细粒、等粒结构的岩石强度高,粗粒、不等粒结构的岩石强度低。研究成果可为掌握矿物粒径对岩石强度及变形特性的影响提供依据。
The whole world has paid more attention to the geological disposal of high-level radioactive waste.Granite is the candidate surrounding rock of high-level radioactive waste disposal project in China. It is very important to understand the strength and destructive characteristics of granite in the design and performance evaluation of disposal system. As aggregates of mineral grains,granite is a heterogeneous rock composed of minerals such as quartz,feldspar and biotite,and the macroscopic mechanical behaviors of rock is obviously affected by mineral grain size. Taking the granites in pre-selected Alxa area of China's high-level geological repository as example,the rock samples have obvious difference in grain size. The effect of grain size on granite mechanical properties is studied using uniaxial compression experiments with the combination of numerical simulation. Uniaxial compression experiments are conducted on MTS815 rock mechanics test system and numerical simulations are based on the particle flow code PFC2 D. In the process of numerical simulation,the actual spatial distribution of various components within the rock ISS obtained by image processing based on the surface image of the specimen. The particle flow model of granite based on the actual distributions is thereafter established. The model is used to simulate the uniaxial compression test of granite,and the reliability of the model is demonstrated by comparison with the experimental results. Experiment and simulation results show that the failure mode of Alxa granite is brittle and tensional. Most failure is parallel to the direction of compressive stress. Numerical simulation based on digital image processing method can be used to calculate the mechanical responses of rock materials with high efficiency and accuracy. Mineral grain size has little effect on elastic modulus and Poisson's ratio of the rock,but peak strength is obviously affected by the grain size. The main results are as follows: The strength of rock with fine grained and equigranular texture is high,and the strength of rock with coarse grained and inequigranular texture is low.
The whole world has paid more attention to the geological disposal of high-level radioactive waste.Granite is the candidate surrounding rock of high-level radioactive waste disposal project in China. It is very important to understand the strength and destructive characteristics of granite in the design and performance evaluation of disposal system. As aggregates of mineral grains,granite is a heterogeneous rock composed of minerals such as quartz,feldspar and biotite,and the macroscopic mechanical behaviors of rock is obviously affected by mineral grain size. Taking the granites in pre-selected Alxa area of China's high-level geological repository as example,the rock samples have obvious difference in grain size. The effect of grain size on granite mechanical properties is studied using uniaxial compression experiments with the combination of numerical simulation. Uniaxial compression experiments are conducted on MTS815 rock mechanics test system and numerical simulations are based on the particle flow code PFC2 D. In the process of numerical simulation,the actual spatial distribution of various components within the rock ISS obtained by image processing based on the surface image of the specimen. The particle flow model of granite based on the actual distributions is thereafter established. The model is used to simulate the uniaxial compression test of granite,and the reliability of the model is demonstrated by comparison with the experimental results. Experiment and simulation results show that the failure mode of Alxa granite is brittle and tensional. Most failure is parallel to the direction of compressive stress. Numerical simulation based on digital image processing method can be used to calculate the mechanical responses of rock materials with high efficiency and accuracy. Mineral grain size has little effect on elastic modulus and Poisson's ratio of the rock,but peak strength is obviously affected by the grain size. The main results are as follows: The strength of rock with fine grained and equigranular texture is high,and the strength of rock with coarse grained and inequigranular texture is low.
引文
Bieniawski Z T.1967.Mechanism of brittle fracture of rock,partⅠ-theory of the fracture process[J].International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts,4(4):395-404.
Bieniawski Z T.1967.Mechanism of brittle fracture of rock,partⅡ-experimental studies[J].International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts,4(4):407-423.
Chen S,Yue Z Q,Tang G H.2005.Digital image based numerical modeling method for heterogeneous geomaterials[J].Chinese Journal of Geotechnical Engineering,27(8):956-964.
Chen S,Yue Z Q,Tang G H.2006.Actual mesostructure based threedimensional numerical modeling method for heterogeneous geomaterials[J].Chinese Journal of Rock Mechanics and Engineering,25(10):1951-1959.
Cundall P A.1971.A computer model for simulating progressive largescale movements in blocky system[C]∥Muller L.Proceedings of Symposium of International Rock Mechanics.Rotterdam:Balkama A.A.,8-12.
Ding X B,Zhang L Y,Zhu H H,et al.2014.Effect of model scale and particle size distribution on PFC3Dsimulation results[J].Rock Mechanics and Rock Engineering,47(6):2139-2156.
Eberhardt E,Stimpson B,Stead D.1999.Effects of grain size on the initiation and propagation thresholds of stress-induced brittle fractures[J].Rock Mechanics and Rock Engineering,32(2):81-99.
Fredrich J T,Evans B,Wong T F.1990.Effect of grain size on brittle and semibrittle strength:implications for micromechanical modelling of failure in compression[J].Journal of Geophysical Research.Part B:Solid Earth,95(B7):10907-10920.
Ishida T,Mizuta Y,Matsunaga I,et al.2000a.Effect of grain size in granitic rock on crack extension in hydraulic fracturing[C]∥Proceedings of the Fourth North American Rock Mechanics Symposium.[S.L.]:American Rock Mechanics Association:1105-1111.
Ishida T,Sasaki S,Matsunaga I,et al.2000b.Effect of grain size in granitic rocks on hydraulic fracturing mechanism[J].Geotechnical Special Publication,290(102):128-139.
Li J Z,Xu J M,Huang D Y,et al.2015.Particle flow simulation of deformation and failure mechanism of granite based on actual distributions of meso-compositions[J].Journal of Engineering Geology,23(S1):84-89.
Nicksiar M,Martin C D.2014.Factors affecting crack initiation in low porosity crystalline rocks[J].Rock Mechanics and Rock Engineering,47(4):1165-1181.
Ohtsu M,Ishida T,Sasaki S.1998.Influence of grain size of granite on hydraulic fracturing mechanism[J].∥Chen Q,Ishida T,Sasaki S,et al.Proceedings of JSCE,589(589):179-194.
Potyondy D O,Cundall P A.2004.A bonded-particle model for rock[J].International Journal of Rock Mechanics&Mining Sciences,41(8):1329-1364.
Sabri M,Ghazvinian A,Nejati H R.2016.Effect of particle size heterogeneity on fracture toughness and failure mechanism of rocks[J].International Journal of Rock Mechanics and Mining Sciences,81:79-85.
Shimizu H,Murata S,Ishida T.2011.The distinct element analysis for hydraulic fracturing in hard rock considering fluid viscosity and particle size distribution[J].International Journal of Rock Mechanics and Mining Sciences,48(5):712-727.
Wang J,Chen W M,Su R,et al.2006.Geological disposal of high-level radioactive waste in and its key scientific issues[J].Chinese Journal of Rock Mechanics and Engineering,25(4):801-812.
Wong R H C,Chan K T,Wang P.1996.Microcracking and grain size effect in Yuen Long marbles[J].International Journal of Rock Mechanics and Mining Science and Geomechanics,33(5):479-485.
You M Q,Su C D.2003.Heterogeneity of rock and the definition of Young's Modulus[J].Chinese Journal of Rock Mechanics and Engineering,22(5):757-761.
Yue Z Q,Chen S,Zheng H,et al.2004.Digital image proceeding based on finite element method for geomaterials[J].Chinese Journal of Rock Mechanics and Engineering,23(6):889-897.
陈沙,岳中琦,谭国焕.2005.基于数字图像的非均质岩土工程材料的数值分析方法[J].岩土工程学报,27(8):956-964.
陈沙,岳中琦,谭国焕.2006.基于真实细观结构的岩土工程材料三维数值分析方法[J].岩石力学与工程学报,25(10):1951-1959.
李进昭,徐金明,黄大勇,等.2015.考虑细观组分实际分布的花岗岩变形破坏过程颗粒流模拟[J].工程地质学报,23(S1):84-89.
王驹,陈伟明,苏锐,等.2006.高放废物地质处置及其若干关键科学问题[J].岩石力学与工程学报,25(4):801-812.
尤明庆,苏承东.2003.岩石的非均质性与杨氏模量的确定方法[J].岩石力学与工程学报,22(5):757-761.
岳中琦,陈沙,郑宏,等.2004.岩土工程材料的数字图像有限元分析[J].岩石力学与工程学报,23(6):889-897.
Bieniawski Z T.1967.Mechanism of brittle fracture of rock,partⅡ-experimental studies[J].International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts,4(4):407-423.
Chen S,Yue Z Q,Tang G H.2005.Digital image based numerical modeling method for heterogeneous geomaterials[J].Chinese Journal of Geotechnical Engineering,27(8):956-964.
Chen S,Yue Z Q,Tang G H.2006.Actual mesostructure based threedimensional numerical modeling method for heterogeneous geomaterials[J].Chinese Journal of Rock Mechanics and Engineering,25(10):1951-1959.
Cundall P A.1971.A computer model for simulating progressive largescale movements in blocky system[C]∥Muller L.Proceedings of Symposium of International Rock Mechanics.Rotterdam:Balkama A.A.,8-12.
Ding X B,Zhang L Y,Zhu H H,et al.2014.Effect of model scale and particle size distribution on PFC3Dsimulation results[J].Rock Mechanics and Rock Engineering,47(6):2139-2156.
Eberhardt E,Stimpson B,Stead D.1999.Effects of grain size on the initiation and propagation thresholds of stress-induced brittle fractures[J].Rock Mechanics and Rock Engineering,32(2):81-99.
Fredrich J T,Evans B,Wong T F.1990.Effect of grain size on brittle and semibrittle strength:implications for micromechanical modelling of failure in compression[J].Journal of Geophysical Research.Part B:Solid Earth,95(B7):10907-10920.
Ishida T,Mizuta Y,Matsunaga I,et al.2000a.Effect of grain size in granitic rock on crack extension in hydraulic fracturing[C]∥Proceedings of the Fourth North American Rock Mechanics Symposium.[S.L.]:American Rock Mechanics Association:1105-1111.
Ishida T,Sasaki S,Matsunaga I,et al.2000b.Effect of grain size in granitic rocks on hydraulic fracturing mechanism[J].Geotechnical Special Publication,290(102):128-139.
Li J Z,Xu J M,Huang D Y,et al.2015.Particle flow simulation of deformation and failure mechanism of granite based on actual distributions of meso-compositions[J].Journal of Engineering Geology,23(S1):84-89.
Nicksiar M,Martin C D.2014.Factors affecting crack initiation in low porosity crystalline rocks[J].Rock Mechanics and Rock Engineering,47(4):1165-1181.
Ohtsu M,Ishida T,Sasaki S.1998.Influence of grain size of granite on hydraulic fracturing mechanism[J].∥Chen Q,Ishida T,Sasaki S,et al.Proceedings of JSCE,589(589):179-194.
Potyondy D O,Cundall P A.2004.A bonded-particle model for rock[J].International Journal of Rock Mechanics&Mining Sciences,41(8):1329-1364.
Sabri M,Ghazvinian A,Nejati H R.2016.Effect of particle size heterogeneity on fracture toughness and failure mechanism of rocks[J].International Journal of Rock Mechanics and Mining Sciences,81:79-85.
Shimizu H,Murata S,Ishida T.2011.The distinct element analysis for hydraulic fracturing in hard rock considering fluid viscosity and particle size distribution[J].International Journal of Rock Mechanics and Mining Sciences,48(5):712-727.
Wang J,Chen W M,Su R,et al.2006.Geological disposal of high-level radioactive waste in and its key scientific issues[J].Chinese Journal of Rock Mechanics and Engineering,25(4):801-812.
Wong R H C,Chan K T,Wang P.1996.Microcracking and grain size effect in Yuen Long marbles[J].International Journal of Rock Mechanics and Mining Science and Geomechanics,33(5):479-485.
You M Q,Su C D.2003.Heterogeneity of rock and the definition of Young's Modulus[J].Chinese Journal of Rock Mechanics and Engineering,22(5):757-761.
Yue Z Q,Chen S,Zheng H,et al.2004.Digital image proceeding based on finite element method for geomaterials[J].Chinese Journal of Rock Mechanics and Engineering,23(6):889-897.
陈沙,岳中琦,谭国焕.2005.基于数字图像的非均质岩土工程材料的数值分析方法[J].岩土工程学报,27(8):956-964.
陈沙,岳中琦,谭国焕.2006.基于真实细观结构的岩土工程材料三维数值分析方法[J].岩石力学与工程学报,25(10):1951-1959.
李进昭,徐金明,黄大勇,等.2015.考虑细观组分实际分布的花岗岩变形破坏过程颗粒流模拟[J].工程地质学报,23(S1):84-89.
王驹,陈伟明,苏锐,等.2006.高放废物地质处置及其若干关键科学问题[J].岩石力学与工程学报,25(4):801-812.
尤明庆,苏承东.2003.岩石的非均质性与杨氏模量的确定方法[J].岩石力学与工程学报,22(5):757-761.
岳中琦,陈沙,郑宏,等.2004.岩土工程材料的数字图像有限元分析[J].岩石力学与工程学报,23(6):889-897.
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