DEM Study on the Instability Behaviour of Granular Materials
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ORIGINAL PAPER
DEM Study on the Instability Behaviour of Granular Materials Krishna Allulakshmi . Jayan S. Vinod . Ana Heitor . Andy Fourie . David Reid
Received: 6 February 2020 / Accepted: 22 October 2020 Ó Springer Nature Switzerland AG 2020
Abstract 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. in Int J Solids Struct 49(10):1252–1258, 2012). The DEM contact parameters have been calibrated to capture the macroscopic responses and the instability behaviour consistently with the laboratory experiments. The effect of different range of initial states at the beginning of CSD
condition such as different initial mean effective stress 0 (p0 ), void ratio (e0 ) 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) has shown a significant influence on the evolution of anisotropic coefficients. An increase in geometric anisotropy and a decrease in mechanical anisotropy with time was observed after the instability. Keywords Discrete element method Constant shear stress Particle scale instability Anisotropy
1 Introduction K. Allulakshmi J. S. Vinod (&) Faculty of Engineering and Information Sciences, University of Wollongong, Wollongong, NSW 2522, Australia e-mail: [email protected] A. Heitor Faculty of Engineering and Physical Sciences, University of Leeds, Leeds LS@ 9DY, UK A. Fourie D. Reid Faculty of Engineering and Mathematical Sciences, University of Western Australia, Crawley, WA 6009, Australia
Water ingress in soils through infiltration can trigger instability leading to failures in slopes and embankments under drained conditions. 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. 2016; Lashkari et al. 2019). Brand (1981) and Sasitharan et al. (1993) have suggested constant shear drained (CSD) triaxial test to predict the
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instability caused by the reduction in effective stress. In the recent past, several researchers have conducted CSD laboratory tests to investigate the instability behaviour of different soils (e.g. Skopek et al. 2011, Anderson and Riemer 1995; Zhu and Anderson 1998; Gajo et al. 2000; Chu et al. 2003, 2012; Nicot et al. 2011; Dong et al. 2016; Rabbi et al
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