CO_2/水孔流作用下砂岩真三轴应变分形特征研究
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摘要
以砂岩为主要研究对象,以CO_2、水为孔隙流体介质,通过真三轴压缩试验得到不同孔流作用下应力应变数据,分析并比较了砂岩受力破坏各个阶段中应变分形曲线特征。研究结果表明:分形维数的突变与应变的突变具有一致性,分形维数的范围与最大值的排序为:干燥>CO_2>水。干燥砂岩的应变分形变化规律为:在孔隙压密阶段,分形维数增大;弹性阶段,分形维数略有上升;屈服阶段,分形维数波动较大;峰后阶段,分形维数减小。含水砂岩和含CO_2砂岩的应变分形规律具有共性和差异性。共性表现在孔隙压密阶段和峰后阶段:孔隙压密阶段两者分形维数减小,峰后阶段两者分形维数增大。差异性体现在中间阶段:含水砂岩的分形维数在很小的范围内波动,而含CO_2砂岩波动较大。试验结果可以在一定程度上定量地反映岩石受力破坏全过程特征,同时给岩石力学行为与破坏机理研究带来新思路。在实际工程中,岩石结构的应变分形结果对其稳定性分析及预测具有指导意义。
aking the sandstone as the main research object,and CO_2 and water as the pore fluid medium,the stress and strain data of sandstone under the effect of different pore fluid were obtained by the true triaxial compression tests,and the characteristics of stain fractal curve in each stage of force and failure for sandstone were analyzed and compared. The results showed that the mutation of fractal dimension was consistent with the mutation of strain,and the range and maximum value of fractal dimension were in the order of dry,CO_2 and water from large to small. The change laws of stain fractal of dry sandstone were: the fractal dimension increased in the pore compaction stage,increased slightly in the elastic stage,fluctuated greatly in the yield stage,and decreased in the post-peak stage. The strain fractal laws of water-bearing sandstone and sandstone containing CO_2 had the characteristics of generality and difference. The generality showed in the pore compaction stage and the post-peak stage,namely both the fractal dimension decreased in the pore compaction stage and increased in the postpeak stage. The difference showed in the middle stages,namely the fractal dimension of the water-bearing sandstone fluctuated in a small range,while the fluctuation of the sandstone containing CO_2 was larger. The test results can quantitatively reflect the whole process characteristics of the rock force and failure in a certain degree,and bring new ideas to the study on rock mechanics behavior and failure mechanism. In the practical engineering,the strain fractal results of rock structure have guiding significance for its stability analysis and prediction.
aking the sandstone as the main research object,and CO_2 and water as the pore fluid medium,the stress and strain data of sandstone under the effect of different pore fluid were obtained by the true triaxial compression tests,and the characteristics of stain fractal curve in each stage of force and failure for sandstone were analyzed and compared. The results showed that the mutation of fractal dimension was consistent with the mutation of strain,and the range and maximum value of fractal dimension were in the order of dry,CO_2 and water from large to small. The change laws of stain fractal of dry sandstone were: the fractal dimension increased in the pore compaction stage,increased slightly in the elastic stage,fluctuated greatly in the yield stage,and decreased in the post-peak stage. The strain fractal laws of water-bearing sandstone and sandstone containing CO_2 had the characteristics of generality and difference. The generality showed in the pore compaction stage and the post-peak stage,namely both the fractal dimension decreased in the pore compaction stage and increased in the postpeak stage. The difference showed in the middle stages,namely the fractal dimension of the water-bearing sandstone fluctuated in a small range,while the fluctuation of the sandstone containing CO_2 was larger. The test results can quantitatively reflect the whole process characteristics of the rock force and failure in a certain degree,and bring new ideas to the study on rock mechanics behavior and failure mechanism. In the practical engineering,the strain fractal results of rock structure have guiding significance for its stability analysis and prediction.
引文
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[13]李伯奎,杨凯,刘远伟.分形理论及分形参数计算方法[J].工具技术,2004,38(12):80-84.LI Bokui,YANG Kai,LIU Yuanwei.Fractal theory and calculation method of fractal parameter[J].Tool Engineering,2004,38(12):80-84.
[14]杨书申,邵龙义.MATLAB环境下图像分形维数的计算[J].中国矿业大学学报,2006,35(4):478-482.YANG Shushen,SHAO Longyi.Estimation of fractal dimensions of images based on MATLAB[J].Journal of China University of Mining&Technology,2006,35(4):478-482.
[15]De Jong S M,Spiers C J,Busch A.Development of swelling strain in smectite clays through exposure to carbon dioxide[J].International Journal of Greenhouse Gas Control,2014,24:149-161.
[2]谢和平.分形力学研究进展[J].力学与实践,1996,18(2):10-18.XIE Heping.Research progress of fractal mechanics[J].Mechanics in Engineering,1996,18(2):10-18.
[3]谢和平,王金安.岩石节理(断裂)表面的多重分形性质[J].力学学报,1998,30(3):58-64.XIE Heping,WANG Jinan.Multifractal behaviors of fracture surfaces in rocks[J].Chinese Journal of Theoretical and Applied Mechanics,1998,30(3):58-64.
[4]谢和平,周宏伟.基于分形理论的岩石节理力学行为研究[J].中国科学基金,1998,12(4):17-22.XIE Heping,ZHOU Hongwei.Research on mechanical behaviors of rock joints based on fractal theory[J].Bulletin of National Natural Science Foundation of China,1998,12(4):17-22.
[5]王金安,谢和平.剪切过程中岩石节理粗糙度分形演化及力学特征[J].岩土工程学报,1997,19(4):2-9.WANG Jinan,XIE Heping.The fractal evolution and mechanical characteristics of rock joint roughness in shear process[J].Chinese Journal of Geotechnical Engineering,1997,19(4):2-9.
[6]谢和平,高峰.岩石类材料损伤演化的分形特征[J].岩石力学与工程学报,1991,10(1):74-82.XIE Heping,GAO Feng.The fractal features of the damage evolution of rock materials[J].Chinese Journal of Rock Mechanics and Engineering,1991,10(1):74-82.
[7]徐志斌,谢和平.断裂尺度的分形分布与其损伤演化的关系[J].地质力学学报,2004,10(3):268-275.XU Zhibin,XIE Heping.Relation between fracture-scale fractal distribution and its damage evolution[J].Journal of Geomechanics,2004,10(3):268-275.
[8]倪玉山,匡震邦,杨英群.常规真三轴压缩下花岗岩断裂表面的分形研究[J].岩石力学与工程学报,1992,11(3):295-303.NI Yushan,KUANG Zhenbang,YANG Yingqun.Fractal study of the fracture surface of grantite caused by triaxial compression[J].Chinese Journal of Rock Mechanics and Engineering,1992,11(3):295-303.
[9]易顺民,唐辉明.三轴压缩条件下三峡坝基岩石破裂的分形特征[J].岩土力学,1999,18(5):24-28.YI Shunmin,TANG Huiming.The fractal characteristics of fracture of dam foundation rock under triaxial compression in the three gorges project[J].Rock and Soil Mechanics,1999,18(5):24-28.
[10]高峰,李建军,李肖音,等.岩石声发射特征的分形分析[J].武汉理工大学学报,2005,27(7):67-69.GAO Feng,LI Jianjun,LI Xiaoyin,et al.Fractal analysis of the characteristics of acoustic emission of rock[J].Journal of Wuhan University of Technology,2005,27(7):67-69.
[11]吴贤振,刘祥鑫,梁正召,等.不同岩石破裂全过程的声发射序列分形特征试验研究[J].岩土力学,2012,33(12):3561-3569.WU Xianzhen,LIU Xiangxin,LIANG Zhengzhao,et al.Experimental study of fractal dimension of AE serials of different rocks under uniaxial compression[J].Rock and Soil Mechanics,2012,33(12):3561-3569.
[12]章光,赵顺利,李墨潇,等.岩石单轴压缩试验的应力应变分形特征研究[J].中国科技论文,2015(9):1038-1042.ZHANG Guang,ZHAO Shunli,LI Moxiao,et al.Research on the fractal characteristic of the rock’s stress and strain under uniaxial compression[J].China Science Paper,2015(9):1038-1042.
[13]李伯奎,杨凯,刘远伟.分形理论及分形参数计算方法[J].工具技术,2004,38(12):80-84.LI Bokui,YANG Kai,LIU Yuanwei.Fractal theory and calculation method of fractal parameter[J].Tool Engineering,2004,38(12):80-84.
[14]杨书申,邵龙义.MATLAB环境下图像分形维数的计算[J].中国矿业大学学报,2006,35(4):478-482.YANG Shushen,SHAO Longyi.Estimation of fractal dimensions of images based on MATLAB[J].Journal of China University of Mining&Technology,2006,35(4):478-482.
[15]De Jong S M,Spiers C J,Busch A.Development of swelling strain in smectite clays through exposure to carbon dioxide[J].International Journal of Greenhouse Gas Control,2014,24:149-161.