A numerical investigation of the incremental behavior of crushable granular soils

Abstract

Summary The mechanical behavior of granular materials is characterized by strong nonlinearity and irreversibility. These properties have been differently described by a variety of constitutive models. To test any constitutive model, experimental data relative to the nature of the incremental stress–strain response of the material is desirable. However, this type of laboratory data is scarce because of being expensive and difficult to obtain. The discrete element method has been used several times as an alternative to obtain incremental responses of granular materials. Crushable grains add one extra source of irreversibility to granular materials. Crushability has been variously incorporated into different constitutive models. Again, it will be helpful to obtain incremental responses of crushable granular materials to test these models, but the experimental difficulties are increased. Making use of a recently introduced crushing model for discrete element simulation, this paper presents a new procedure to obtain incremental responses in discrete analogs of granular crushable materials. The parallel probe approach, previously used for uncrushable discrete analogs, is here extended to account for the presence of crushable grains. The contribution of grain crushing to the incremental irreversible strain is identified and separately measured. Robustness of the proposed method is examined in detail, paying particular attention to aspects such as dynamic instability or crushing localization. The proposed procedure is later applied to map incremental responses of a discrete analog of Fontainebleau sand on the triaxial plane. The effect of stress ratio and granular state on plastic flow characteristics is highlighted. Copyright © 2016 John Wiley & Sons, Ltd.

Micromechanical inspection of incremental behaviour of crushable soils

“…The crushed fragments assume the velocity and material parameters of the original particle apart from the intrinsic strength (r lim0 ) which is randomly assigned sampling its normal distribution. Ciantia et al [15,16] concluded that a 14-ball crushed configuration can adequately represent macroscopic behaviour. The capability of this model to capture real test behaviour has been demonstrated by Ciantia et al [14,17].…”

“…Ciantia et al [16] used a DEM model based on the splitting particle concept to explore the incremental response of crushable soils. They showed that grain crushing causes the plastic flow to change direction and that this direction is unique and independent on the loading direction.…”

“…Taking advantage of the efficiency of the DEM crushing model of Ciantia et al [16], results have been obtained from a large number of simulations ([ 350). In what follows the DEM model is first described; the methods applied for micromechanical investigation are then introduced before presenting some relevant numerical results.…”

Micro mechanics of drained and undrained shearing of compacted and overconsolidated crushable sand

“…There have been several efforts to use the discrete-element method (DEM) to model and investigate the general shearing behaviour of soil using crushable particles (e.g. Abe & Mair, 2005;Lobo-Guerrero et al, 2006;Wood & Maeda, 2008;Marketos & Bolton, 2009;Elghezal et al, 2013;Wang & Yan, 2013;Ciantia et al, 2016). In particular, a number of recent attempts have been made to investigate the three-dimensional triaxial behaviour of crushable soil (e.g.…”

“…This can be overcome by using the alternative approach of replacing breaking particles with smaller particles of the same shape, such as by de Bono & McDowell (2014) and Hanley et al (2015), who both provided overviews of the effects of crushing, and established critical state lines (CSLs) from triaxial tests. Ciantia et al (2016) also performed shear tests using the particle replacement method; however, their study focused on the plastic flow and response to strain probes, rather than critical states.…”