Instability of Particulate Assemblies under Constant Shear Drained Stress Path: DEM Approach

Lashkari, Ali; Khodadadi, Mitra; Binesh, S.M.; Rahman, M.F.

doi:10.1061/(asce)gm.1943-5622.0001407

Cited by 36 publications

(16 citation statements)

References 55 publications

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“…After that, the increase in axial strain rate has begun indicating instability, and axial strain has shown a steady increase with the corresponding decrease in 𝑝 ′ . Similar response of 𝜀 𝑎 against 𝑝 ′ was also shown by Lashkari et al (2019). Whereas, the 𝑒 -𝑝 ′ plot shows an instant change in the behaviour once the CSD is imposed, the void ratio starts developing due to the rebound (relaxation) phenomena experienced by the soil with the decrease of mean effective stress under constant deviatoric stress.…”

Section: Effect Of 𝒒 On the Instability Pointsupporting

confidence: 67%

“…Subsequent investigations on such failures have shown that the infiltration of water in soils can cause a reduction in effective stress leading to the instability of slopes and embankments (e.g. Eckersley 1990;Olson et al 2000;Dong et al 2015;Lashkari et al 2019). Brand (1981) and Sasitharan et al (1993) have suggested constant shear drained (CSD) triaxial test to predict the instability caused by the reduction in effective stress.…”

Section: Introductionmentioning

confidence: 99%

“…Based on Hill's criterion, the material is stable if the second increment of work is strictly positive (𝑑 2 𝑊 > 0) for all changes in stresses and strains (Darve et al 2004). In addition, many constitutive models have also incorporated Hill's instability criterion to capture the instability during CSD tests (Ramos et al 2012;Alipour and Lashkari 2017;Lashkari et al 2019). Recently, Nicot et al (2012) have proposed a microscopic formulation for the second order work as a combination of contact forces and resultant particle forces.…”

Section: Introductionmentioning

confidence: 99%

“…The Discrete Element Method (DEM) developed by Cundall and Strack (1979) is an alternative to the continuum mechanics approach for modelling and analysing the soil mechanical behaviour at a particle scale level. Even though many experimental CSD analyses have been conducted on the instability of granular materials, only, limited studies were performed to simulate the CSD test using micromechanical based approaches such as DEM (Ning et al 2013;Perez et al 2016;Lashkari et al 2019). Perez et al (2016) and Lashkari et al (2019) have adopted a stress controlled loading in their analyses and identified the instability behaviour based on Hill's particle scale criterion and strain rate increment.…”

Section: Introductionmentioning

confidence: 99%

“…Even though many experimental CSD analyses have been conducted on the instability of granular materials, only, limited studies were performed to simulate the CSD test using micromechanical based approaches such as DEM (Ning et al 2013;Perez et al 2016;Lashkari et al 2019). Perez et al (2016) and Lashkari et al (2019) have adopted a stress controlled loading in their analyses and identified the instability behaviour based on Hill's particle scale criterion and strain rate increment. Furthermore, they simulated the evolution of micromechanical quantities (coordination number, anisotropic coefficients) and highlighted the behavioural change of micro parameters post the instability point.…”

Section: Introductionmentioning

confidence: 99%

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DEM Study on the Instability Behaviour of Granular Materials

et al. 2020

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This paper presents the Discrete Element Method (DEM) simulations on the instability behaviour of granular materials during Constant Shear Drained condition (CSD). CSD condition was implemented by decreasing mean effective stress on an assembly of particles under strain controlled loading. In this study, the instability condition was predicted at the particle scale level using particle second order work increment (Nicot et al., 2012). The DEM contact parameters have been calibrated to capture the macroscopic responses and the instability behaviour consistently with the laboratory experimental observations. Using the same contact parameters the effect of different range of initial states at the beginning of CSD condition such as different initial mean effective stress (𝑝 0 ′ ), void ratio (𝑒 0 ) and deviatoric stress (𝑞) on the instability behaviour were analysed. In addition, the micromechanical parameters such as coordination number, anisotropic coefficients (geometric, mechanical) have been extracted to assist in characterising the instability behaviour during CSD condition. The initial stress state of the soil (i.e. at the onset of CSD) condition has shown a significant influence on the evolution of anisotropic coefficients, an evident behaviour change was noted once the CSD condition is imposed. A continuous increase of geometric anisotropy, and a gradual decrease of mechanical anisotropy was observed after the instability condition is reached.

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Section: Effect Of 𝒒 On the Instability Pointsupporting

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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DEM Study on the Instability Behaviour of Granular Materials

et al. 2020

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Effects of reconsolidation degree on reliquefaction resistance under mainshock–aftershock sequences: A DEM investigation

Xie

Zhao

2022

Num Anal Meth Geomechanics

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Aftershock events may immediately follow mainshock events. In liquefiable deposits, the excess pore pressure caused by mainshock events may not dissipate completely in a short time interval between the mainshock and the aftershock. Sandy soil with different reconsolidation degrees (Ur) may present different reliquefaction resistances during the aftershock, which was not fully considered into the previous studies of reliquefaction. In this study, discrete element method (DEM) was employed to simulate a series of cyclic triaxial tests to evaluate the effects of Ur on reliquefaction resistance under mainshock–aftershock seismic sequence. The initially liquefied specimen was reconsolidated from two states with small and large residual shear strain respectively. Reconsolidated specimens reliquefied under different cyclic stress ratios (CSRs). Simulation results show that reliquefaction resistance increased gradually with increasing Ur, which was closely related to the previous residual shear strain during the first liquefaction event. Specimens that having large residual shear strain reliquefied easily, and the reliquefaction resistance of those specimens increased slightly with increasing Ur. On the contrary, reliquefaction resistance of the specimens that having small residual shear stain increased obviously with increasing Ur. The ratio of initial mechanical average coordination number to initial mesoscopic fabric anisotropy of reconsolidated specimens had a good correlation to the contraction potential and increased gradually with increasing Ur.

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Instability of binary mixtures subjected to constant shear drained stress path: Insight from macro and micro perspective

Yan,

Liu,

Zhao

2024

Num Anal Meth Geomechanics

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Loose granular materials may also exhibit instability behaviors similar to liquefaction under drained conditions, commonly referred to as diffuse instability, which can be studied through constant shear drained (CSD) tests. So far, the research on CSD in binary mixtures is still insufficient. Therefore, a series of numerical tests using the discrete element method (DEM) were conducted on binary mixtures under CSD path. The possible model of instability is categorized into type I and type II, type I instability occurs prior to reaching the critical state line (CSL), whereas type II instability occurs after exceeding the CSL. The study analyzes the macroscopic instability behavior and the impact of fine content (FC) on macroscopic instability behavior. The numerical results show that as FC increases, the slope of the instability line (IL) increases initially and then falls in the p‐q plane. In the e‐p plane, the IL decreases initially and then ascends. The instability type of the binary mixtures is influenced not only by relative density but also by FC. The stability index increased first and then decreased with the increase of FC. The microscopic origin of binary mixtures instability is explored by investigating the fabric‐stress relationship. The collapse of the weak contact sub‐network triggers the specimen instability, while the strong contact sub‐network dictates the difficulty of achieving instability. FC influences the evolution of fabric anisotropy of the strong and weak contact networks, thereby controlling the macroscopic instability behavior of binary mixtures.

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Instability of Particulate Assemblies under Constant Shear Drained Stress Path: DEM Approach

Cited by 36 publications

References 55 publications

DEM Study on the Instability Behaviour of Granular Materials

DEM Study on the Instability Behaviour of Granular Materials

Effects of reconsolidation degree on reliquefaction resistance under mainshock–aftershock sequences: A DEM investigation

Instability of binary mixtures subjected to constant shear drained stress path: Insight from macro and micro perspective

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