scholarly journals A critical state based viscoplastic model for crushable granular materials

2022 ◽  
Vol 62 (1) ◽  
pp. 101093
Author(s):  
Soukat Kumar Das ◽  
Arghya Das
Keyword(s):  
Granular Materials ◽  
Critical State ◽  
Viscoplastic Model

scholarly journals Grain roughness effect on the critical state line of crushable sands

2021 ◽  
Author(s):  
Jiangtao Lei ◽  
◽  
Marcos Arroyo ◽  
Matteo Ciantia ◽  
Ningning Zhang ◽  
...  
Keyword(s):  
Granular Materials ◽  
Critical State ◽  
Roughness Effect ◽  
Dem Simulation ◽  
Dem Model ◽  
Grain Roughness

A recently proposed DEM model for materials with rough crushable grains (Zhang et al. 2021; Ciantia et al. 2015; Otsubo et al. 2017) is here employed to examine the effect of contact roughness on the critical state line, a property of granular materials which is a) fundamental for the evaluation of liquefaction risk and liquefied responses and b) easily accessible through DEM simulation (Ciantia et al. 2019).

scholarly journals Prediction of Shear Localisation in Granular Materials based on a Critical State Non-coaxial Model

2019 ◽  
Vol 92 ◽  
pp. 16006 ◽  
Author(s):  
Hansini Mallikarachchi ◽  
Kenichi Soga
Keyword(s):  
Granular Materials ◽  
Plane Strain ◽  
Critical State ◽  
Progressive Failure ◽  
Shear Bands ◽  
State Parameter ◽  
Biaxial Compression ◽  
Compression Tests ◽  
Principal Axes ◽  
Shear Localisation

Experimental evidence indicates that the shear localisation acts as a precursor to the failure in biaxial compression tests of granular materials. Once formed they are persistent and lead to progressive failure of most geotechnical structures. It is generally accepted that the primary mode of deformation within these shear bands is simple shear which is accompanied by rotation of principal axes. Hence, the conventional plasticity theories based on the assumption of coaxility is not sufficient to describe the behaviour within those shear bands. This paper highlights the influence of the non-coaxility on the initiation and orientation of shear bands in both drained and undrained sand. The con-coaxial plasticity theory is integrated into a critical state constitutive model enriched with the state parameter concept. The model is capable of taking account of the variation of lode angle under plane strain condition. Numerical plane strain biaxial compression tests are conducted to observe the effect of non-coaxility on shear localisation. Bifurcation criteria based on the acoustic tensor are checked to predict the onset and inclination of the shear band. Predictions from the non-coaxial model are compared with those of coaxial model. The influence of the initial void ratio for the formation of shear bands is explored. Results are compared qualitatively with experimental observations.

A numerical assessment of strain rate effects on the critical state of crushable granular materials

2022 ◽  
Vol 12 (1) ◽  
pp. 1-19
Author(s):  
S.K. Das ◽  
S.K. Verma ◽  
A. Das
Keyword(s):  
Strain Rate ◽  
Granular Materials ◽  
Critical State ◽  
Triaxial Tests ◽  
Particle Crushing ◽  
Confining Stress ◽  
Stress Strain ◽  
Strain Rate Effects ◽  
Coral Sand ◽  
Rate Effects

The present study highlights the effects of strain rate on the critical state response of crushable granular materials. A set of drained triaxial tests is simulated using the discrete element method (DEM) to understand the rate effects on the stress-strain and volumetric behaviour of the granular sample. The DEM parameters are obtained by comparing the stress-strain and particle crushing behaviour of in-house experimental analysis on crushable coral sand under a slow strain rate. In DEM, the particles are subjected to varied strain rates under different initial confining pressures and initial densities to capture the rate effects on the macroscopic responses until the critical state. It is seen that crushing increases with increasing confining stress. However, a higher strain rate induces relatively lower crushing and higher strength in terms of both peak stress and residual stress. It is observed that in pressure-volume space, the critical state line alters with the increasing strain rate of the crushable samples, especially at high confining conditions, whereas strain rate effect on critical state seems to be negligible at low confining conditions due to the absence of particle crushing.

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