Pub Date : 2024-05-08DOI: 10.1007/s11440-024-02331-x
M. Salimi, A. Lashkari, M. Tafili
The discrete element method (DEM) is employed to investigate the impact of coupling between volumetric and axial strains on the flow liquefaction vulnerability of 3D cubic particulate specimens. The virtual testing program conducted here encompasses a wide range of initial states and varying degrees of coupling between volumetric and axial strains. Utilizing data obtained from DEM simulations, the evolution of micro- and macroscale variables, including coordination number, contact fabric anisotropy, redundancy index, strong force networks, invariants of the effective stress tensor, and excess pore-water pressure, is examined. Results from DEM tests indicate that coupling expansive volumetric strain with axial strain leads to a gradual loosening of the load bearing microstructure, a decrease in coordination number, and a faster change in contact anisotropy. DEM simulations demonstrate that the triggering of flow liquefaction instability is followed by a sudden increase in contact fabric anisotropy and abrupt drops in coordination number and redundancy index. Moreover, a detailed analysis of the findings suggests that the stress ratio at the onset of post-peak softening decreases with increasing expansive volumetric strains.
本文采用离散元素法(DEM)研究了体积应变和轴向应变之间的耦合对三维立方颗粒试样流动液化脆弱性的影响。这里进行的虚拟测试程序包括多种初始状态以及体积应变和轴向应变之间不同程度的耦合。利用从 DEM 模拟中获得的数据,研究了微观和宏观变量的演变,包括配位数、接触织物各向异性、冗余指数、强力网络、有效应力张量不变量和过剩孔隙水压力。DEM 试验结果表明,膨胀性体积应变与轴向应变的耦合会导致承载微观结构的逐渐松动、配位数的减少以及接触各向异性的快速变化。DEM 模拟表明,在触发流动液化不稳定性后,接触织物各向异性会突然增加,配位数和冗余指数会突然下降。此外,对研究结果的详细分析表明,峰后软化开始时的应力比会随着膨胀体积应变的增加而减小。
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Pub Date : 2024-05-08DOI: 10.1007/s11440-024-02339-3
Andrzej Głuchowski, Linzhu Li, Magued Iskander
<div><p>Changes in particle granulometry could lead to significant changes in a soil’s behavior, making an understanding of micro-scale granulometry essential for practical applications. Changes in particle size, shape, and particle size distribution could result from a combination of applied normal and shearing stresses, which can in turn influence further response of the material. This study explored particle breakage during both compressive and shear loading under typical stresses. A deeper understanding of the phenomenon requires distinguishing broken and unbroken grains at the particle scale. Dynamic Image Analysis (DIA) was therefore employed to quantify changes in particle granulometry in two sands, a siliceous Ottawa sand and a calcareous sand known as Fiji Pink. Pre-sorted specimens having similar size, granulometry, and particle size distributions were tested using both oedometric and direct shear tests having the same aspect ratio, facilitating a direct comparison of the effects of shearing and compression on similar materials having different mineralogy. A breakage index was used for prognosis of particle breakage at key reference diameters. During oedometric tests, grain breakage was limited in both sands at stresses up to 1.2 MPa, but it increased significantly during direct shear tests. A conceptual model was proposed to explain the particle breakage mechanism during shear, at four key phase points representing (1) maximum compaction, (2) transition from compaction to dilative behavior, (3) maximum shear stress, and (4) peak test strain. In addition, a loading intensity framework was adopted to explain the relative roles of normal and shearing stresses on particle breakage. An increase of fines in soil during shearing was also observed and related to two sources: coarser grain abrasion and finer particle crushing. The vulnerability of grains with more anisotropic shapes was also observed. The loading intensity framework suggested that attrition of particle diameter could be divided into two phases, with a transitional critical loading intensity that appeared constant for each sand. For Ottawa sand, abrasion was the primary mechanism observed, causing a significant increase in Aspect Ratio (<i>AR</i>) and Sphericity (<i>S</i>) for finer grains. For Fiji sand, a transition from abrasion to attrition was noted, leading to limited sphericity decrease for the largest particles. Finer particles cushioning larger Fiji sand particles are more prone to breakage, resulting in increased <i>AR</i> and <i>S</i>. Finally, test results were used to propose a simple hyperbolic model to predict
{"title":"Effect of compression and shear on particle\u0000 breakage of silica and calcareous sands","authors":"Andrzej Głuchowski, Linzhu Li, Magued Iskander","doi":"10.1007/s11440-024-02339-3","DOIUrl":"10.1007/s11440-024-02339-3","url":null,"abstract":"<div><p>Changes in particle granulometry could lead to significant changes in a\u0000 soil’s behavior, making an understanding of micro-scale granulometry essential for\u0000 practical applications. Changes in particle size, shape, and particle size distribution\u0000 could result from a combination of applied normal and shearing stresses, which can in\u0000 turn influence further response of the material. This study explored particle breakage\u0000 during both compressive and shear loading under typical stresses. A deeper understanding\u0000 of the phenomenon requires distinguishing broken and unbroken grains at the particle\u0000 scale. Dynamic Image Analysis (DIA) was therefore employed to quantify changes in\u0000 particle granulometry in two sands, a siliceous Ottawa sand and a calcareous sand known\u0000 as Fiji Pink. Pre-sorted specimens having similar size, granulometry, and particle size\u0000 distributions were tested using both oedometric and direct shear tests having the same\u0000 aspect ratio, facilitating a direct comparison of the effects of shearing and\u0000 compression on similar materials having different mineralogy. A breakage index was used\u0000 for prognosis of particle breakage at key reference diameters. During oedometric tests,\u0000 grain breakage was limited in both sands at stresses up to 1.2 MPa, but it increased\u0000 significantly during direct shear tests. A conceptual model was proposed to explain the\u0000 particle breakage mechanism during shear, at four key phase points representing (1)\u0000 maximum compaction, (2) transition from compaction to dilative behavior, (3) maximum\u0000 shear stress, and (4) peak test strain. In addition, a loading intensity framework was\u0000 adopted to explain the relative roles of normal and shearing stresses on particle\u0000 breakage. An increase of fines in soil during shearing was also observed and related to\u0000 two sources: coarser grain abrasion and finer particle crushing. The vulnerability of\u0000 grains with more anisotropic shapes was also observed. The loading intensity framework\u0000 suggested that attrition of particle diameter could be divided into two phases, with a\u0000 transitional critical loading intensity that appeared constant for each sand. For Ottawa\u0000 sand, abrasion was the primary mechanism observed, causing a significant increase in\u0000 Aspect Ratio (<i>AR</i>) and Sphericity (<i>S</i>) for finer grains. For Fiji sand, a transition from\u0000 abrasion to attrition was noted, leading to limited sphericity decrease for the largest\u0000 particles. Finer particles cushioning larger Fiji sand particles are more prone to\u0000 breakage, resulting in increased <i>AR</i> and <i>S</i>. Finally, test results were used to propose a simple\u0000 hyperbolic model to predict ","PeriodicalId":49308,"journal":{"name":"Acta Geotechnica","volume":"19 11","pages":"1 - 27"},"PeriodicalIF":5.6,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140935912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}