低围压下颗粒形态对软黏土抗剪强度影响的离散元分析
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摘要
黏土颗粒形态不仅反映黏土的矿物组分,更是影响其物理力学性质的重要因素之一。为了研究物质组成对软黏土微宏观性质的影响,采用离散元方法对不同颗粒形态的软黏土试样进行三轴压缩模拟试验。首先,基于扫描电镜图像量化颗粒形态,对天然状态下黏土颗粒的方向角和凹凸度进行统计,引入球度和凹凸度作为颗粒形态的特征参数;然后,基于原生矿物的单粒结构和黏土矿物的片状结构特征,构造球体单粒及圆柱体、正方体、长方体的片状簇体;最后,基于三轴试验离散元模拟方法,分析软黏土颗粒形态对其宏观力学及微观特性的影响。结果表明:片状颗粒试样比球体颗粒试样的初始模量高,抗剪强度大,随加载其排列趋于水平向分布;加载初期,颗粒球度对初始弹性模量影响较明显,初始弹性模量随着球度增大而逐渐减小;加载后期,颗粒凹凸度对抗剪强度指标影响作用逐渐凸显,试样内摩擦角和黏聚力随着凹凸度增大而逐渐减小;微观结构上,颗粒形状对颗粒位移和旋转也有较大影响。
The morphology of clay particles not only reflects the mineral composition of clay,but also is one of the important factors affecting its physical and mechanical properties. In order to study the effect of material composition on the micro-macro properties of clay,we use the discrete element method to simulate the triaxial compression of soft clay samples with different particle morphology. Firstly,based on the SEM image,the orientation angle and concave convexity of clay particles in natural state are counted. The sphericity and concave-convexity are introduced as the characteristic parameters of particle morphology. Secondly,we construct a clay particle model based on the structural features of clay minerals that we count at the first step. Finally,with triaxial test discrete element simulation method,we analyze the effect of soft clay particle morphology on its macroscopic mechanical and microscopic properties. The results show that the flaky particle sample has higher initial modulus than the spherical particle sample,and the shear strength is larger. The flaky particle sample even tends to be horizontally distributed with the loading. We divide the loading processes into two stages as the clay particle model showing different characteristics in each stage. At the initial stage of loading,the sphericity of particles has a significant effect on the initial elastic modulus,and the initial elastic modulus decreases with the increase of sphericity. At the later stage of loading,the effect of concave and convex degree of particles on shear strength index is gradually obvious,and the internal friction angle and cohesion of samples decrease with the increase of concave and convex degree.Microscopically,the shape of particles also has a great influence on the displacement and rotation of particles.
The morphology of clay particles not only reflects the mineral composition of clay,but also is one of the important factors affecting its physical and mechanical properties. In order to study the effect of material composition on the micro-macro properties of clay,we use the discrete element method to simulate the triaxial compression of soft clay samples with different particle morphology. Firstly,based on the SEM image,the orientation angle and concave convexity of clay particles in natural state are counted. The sphericity and concave-convexity are introduced as the characteristic parameters of particle morphology. Secondly,we construct a clay particle model based on the structural features of clay minerals that we count at the first step. Finally,with triaxial test discrete element simulation method,we analyze the effect of soft clay particle morphology on its macroscopic mechanical and microscopic properties. The results show that the flaky particle sample has higher initial modulus than the spherical particle sample,and the shear strength is larger. The flaky particle sample even tends to be horizontally distributed with the loading. We divide the loading processes into two stages as the clay particle model showing different characteristics in each stage. At the initial stage of loading,the sphericity of particles has a significant effect on the initial elastic modulus,and the initial elastic modulus decreases with the increase of sphericity. At the later stage of loading,the effect of concave and convex degree of particles on shear strength index is gradually obvious,and the internal friction angle and cohesion of samples decrease with the increase of concave and convex degree.Microscopically,the shape of particles also has a great influence on the displacement and rotation of particles.
引文
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Asadi M,Thoeni K,Mahboubi A.2018.An experimental and numerical study on the compressive behavior of sand-rubber particle mixtures[J].Computers and Geotechnics,104:185-195．
Chang Z.2008.Theoretical and numerical research on granular mechanics of soils[D].Beijing:Tsinghua University．
Chen J F,Li H L,Zhou J.2010.Study on the relevance of macro-micro parameters for clays[J].Chinese Quarterly of Mechanics,31(2):304-309．
Gao Y B,Wang J F,Ye G B,et al.2009.PFC numerical simulation on anisotropic properties of cohesive soil[J].Journal of Engineering Geology,17(5):638-642．
Garcia F E,Bray J D.2019.Modeling the shear response of granular materials with discrete element assemblages of sphere-clusters[J].Computers and Geotechnics,106:99-107．
Gu X Q,Huang M S,Qian J G.2014.Discrete element modeling of shear band in granular materials[J].Theoretical and Applied Fracture Mechanics,72:37-49．
Ha Giang P H,Van Impe P O,Van Impe W F,et al.2017.Small-strain shear modulus of calcareous sand and its dependence on particle characteristics and gradation[J].Soil Dynamics and Earthquake Engineering,100:371-379．
Hosseininia E S.2012.Discrete element modeling of inherently anisotropic granular assemblies with polygonal particles[J].Particuology,10(5):542-552．
Kong L,Peng R.2011.Particle flow simulation of influence of particles shape on mechanical properties of quasi-sands[J].Chinese Journal of Rock Mechanics and Engineering,30(10):2112-2119．
Le T C,Gu Y F,Liu C,et al.2018.Experiment and DEM numerical simulation for influence of particle size distribution and shape on compressibility of sand[J].Journal of Engineering Geology,26(S1):539-546．
Liu Z Q,Song J,Li X,et al.2017.Three-dimensional characterization of mineral and organic compositions in process of consolidation of saturated fine-grained soil[J].Journal of Engineering Geology,25(5):1299-1306．
Wang X B,Bai X Y,Zhang B W,et al.2018.Experimental studies of shear dilatancy of shear bands for wet clay specimens in uniaxial compression using digital image correlation method[J].Journal of Engineering Geology,26(4):882-890．
Zeng Y,Zhou J.2008.Influence of micro parameters of sandy soil on its macro properties[J].Chinese Journal of Underground Space and Engineering,4(3):499-503．
Zheng B N,Ding D Y,Zhang D,et al.2019.CT scanning and PFCmodeling combined 3D method for gravel-bearing slip soil[J].Journal of Engineering Geology,27(3):569-576．
Zhou J,Yu R C,Jia M C.2006.Measurement of microstructure parameters for granular soil model using digital image technology[J].Chinese Journal of Geotechnical Engineering,28(12):2047-2052．
Zhou L L,Chu X H,Xu Y J.2017.Breakage behavior of sand under true triaxial stress based on discrete element method[J].Chinese Journal of Geotechnical Engineering,39(5):839-847．
常在．2008．土的颗粒力学理论及数值模拟[D]．北京:清华大学．
陈建峰，李辉利，周健．2010．黏性土宏细观参数相关性研究[J]．力学季刊，31(2):304-309．
高彦斌，王江锋，叶观宝，等．2009．黏性土各向异性特性的PFC数值模拟[J]．工程地质学报，17(5):638-642．
孔亮，彭仁．2011．颗粒形状对类砂土力学性质影响的颗粒流模拟[J]．岩石力学与工程学报，30(10):2112-2119．
乐天呈，顾颖凡，刘春，等．2018．级配与颗粒形态对砂土压缩性影响的试验和离散元数值模拟[J]．工程地质学报，26(S1):539-546．
刘治清，宋晶，李学，等．2017．饱和细粒土固结过程中矿物组分与有机质的三维表征[J]．工程地质学报，25(5):1299-1306．
王学滨，白雪元，张博闻，等．2018．基于数字图像相关方法的单轴压缩黏土试样剪切带剪胀实验研究[J]．工程地质学报，26(4):882-890．
郑博宁，丁大勇，张丹，等．2019．含砾滑带土三维颗粒流模型建模方法研究[J]．工程地质学报，27(3):569-576．
曾远，周健．2008．砂土的细观参数对宏观特性的影响研究[J]．地下空间与工程学报，4(3):499-503．
周健，余荣传，贾敏才．2006．基于数字图像技术的砂土模型试验细观结构参数测量[J]．岩土工程学报，28(12),2047-2052．
周伦伦，楚锡华，徐远杰．2017．基于离散元法的真三轴应力状态下砂土破碎行为研究[J]．岩土工程学报，39(5):839-847.
Asadi M,Thoeni K,Mahboubi A.2018.An experimental and numerical study on the compressive behavior of sand-rubber particle mixtures[J].Computers and Geotechnics,104:185-195．
Chang Z.2008.Theoretical and numerical research on granular mechanics of soils[D].Beijing:Tsinghua University．
Chen J F,Li H L,Zhou J.2010.Study on the relevance of macro-micro parameters for clays[J].Chinese Quarterly of Mechanics,31(2):304-309．
Gao Y B,Wang J F,Ye G B,et al.2009.PFC numerical simulation on anisotropic properties of cohesive soil[J].Journal of Engineering Geology,17(5):638-642．
Garcia F E,Bray J D.2019.Modeling the shear response of granular materials with discrete element assemblages of sphere-clusters[J].Computers and Geotechnics,106:99-107．
Gu X Q,Huang M S,Qian J G.2014.Discrete element modeling of shear band in granular materials[J].Theoretical and Applied Fracture Mechanics,72:37-49．
Ha Giang P H,Van Impe P O,Van Impe W F,et al.2017.Small-strain shear modulus of calcareous sand and its dependence on particle characteristics and gradation[J].Soil Dynamics and Earthquake Engineering,100:371-379．
Hosseininia E S.2012.Discrete element modeling of inherently anisotropic granular assemblies with polygonal particles[J].Particuology,10(5):542-552．
Kong L,Peng R.2011.Particle flow simulation of influence of particles shape on mechanical properties of quasi-sands[J].Chinese Journal of Rock Mechanics and Engineering,30(10):2112-2119．
Le T C,Gu Y F,Liu C,et al.2018.Experiment and DEM numerical simulation for influence of particle size distribution and shape on compressibility of sand[J].Journal of Engineering Geology,26(S1):539-546．
Liu Z Q,Song J,Li X,et al.2017.Three-dimensional characterization of mineral and organic compositions in process of consolidation of saturated fine-grained soil[J].Journal of Engineering Geology,25(5):1299-1306．
Wang X B,Bai X Y,Zhang B W,et al.2018.Experimental studies of shear dilatancy of shear bands for wet clay specimens in uniaxial compression using digital image correlation method[J].Journal of Engineering Geology,26(4):882-890．
Zeng Y,Zhou J.2008.Influence of micro parameters of sandy soil on its macro properties[J].Chinese Journal of Underground Space and Engineering,4(3):499-503．
Zheng B N,Ding D Y,Zhang D,et al.2019.CT scanning and PFCmodeling combined 3D method for gravel-bearing slip soil[J].Journal of Engineering Geology,27(3):569-576．
Zhou J,Yu R C,Jia M C.2006.Measurement of microstructure parameters for granular soil model using digital image technology[J].Chinese Journal of Geotechnical Engineering,28(12):2047-2052．
Zhou L L,Chu X H,Xu Y J.2017.Breakage behavior of sand under true triaxial stress based on discrete element method[J].Chinese Journal of Geotechnical Engineering,39(5):839-847．
常在．2008．土的颗粒力学理论及数值模拟[D]．北京:清华大学．
陈建峰，李辉利，周健．2010．黏性土宏细观参数相关性研究[J]．力学季刊，31(2):304-309．
高彦斌，王江锋，叶观宝，等．2009．黏性土各向异性特性的PFC数值模拟[J]．工程地质学报，17(5):638-642．
孔亮，彭仁．2011．颗粒形状对类砂土力学性质影响的颗粒流模拟[J]．岩石力学与工程学报，30(10):2112-2119．
乐天呈，顾颖凡，刘春，等．2018．级配与颗粒形态对砂土压缩性影响的试验和离散元数值模拟[J]．工程地质学报，26(S1):539-546．
刘治清，宋晶，李学，等．2017．饱和细粒土固结过程中矿物组分与有机质的三维表征[J]．工程地质学报，25(5):1299-1306．
王学滨，白雪元，张博闻，等．2018．基于数字图像相关方法的单轴压缩黏土试样剪切带剪胀实验研究[J]．工程地质学报，26(4):882-890．
郑博宁，丁大勇，张丹，等．2019．含砾滑带土三维颗粒流模型建模方法研究[J]．工程地质学报，27(3):569-576．
曾远，周健．2008．砂土的细观参数对宏观特性的影响研究[J]．地下空间与工程学报，4(3):499-503．
周健，余荣传，贾敏才．2006．基于数字图像技术的砂土模型试验细观结构参数测量[J]．岩土工程学报，28(12),2047-2052．
周伦伦，楚锡华，徐远杰．2017．基于离散元法的真三轴应力状态下砂土破碎行为研究[J]．岩土工程学报，39(5):839-847.
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