Relating fragmentation, plastic work and critical state in crushable rock clasts

Abstract

Grain breakage during compression and shearing is one important mechanism responsible for irrecoverable changes of the mechanical properties of granular materials. Here we present results of triaxial tests on limestone fragments under some monotonic and cyclic stress paths and we investigate the relationships between the progression of grain breakage, the plastic work and the evolution of the critical state line. Using the plastic work concept, we propose a method for determining grain shape and grain breakage indices, and we show how grain breakage influences the critical stress state, and hence the mechanical behavio ur. The validity of the relationships is then verified on different granular assemblies (granite fragments and quartz sands), although further tests remain necessary to validate them under more generic stress paths.

An Empirical Power Density‐Based Friction Law and Its Implications for Coherent Landslide Mobility

“…This has also been demonstrated in experiments (Hou et al, 2012; Yao, Ma, et al, 2013), yet a pure velocity‐dependent approach still neglects the variability of the normal stress. For example, the thickness of the failed mass in the Jiweishan landslide varied spatially from 50 to 80 m (Hu, Yin, et al, 2018). This may have affected its runout behavior as different evolutions of the friction coefficient may be associated with different thicknesses.…”

“…Shear‐weakening mechanisms in the basal layer of coherent landslides and, more limitedly, in partially coherent landslides may be studied through high‐velocity shear experiments, which can reproduce the stress states occurring during landslide runout. Energy dissipation in high‐velocity shear experiments can arise from grain crushing (Hu, Yin, et al, 2018; Zhang et al, 2018) and heat generation. Some energy can also be consumed in endothermic reactions, namely thermal decomposition, and dehydration.…”

Mineralogical Analysis of Selective Melting in Partially Coherent Rockslides: Bridging Solid and Molten Friction

“…In Figure 4, in the initial frictional weakening stage, a decrease in friction coefficient occurred, from a peak value of 0.69 consistent with Byerlee's range 0.6–0.85) to a steady‐state coefficient of 0.17 (Byerlee, 1968; Deng et al, 2020). This frictional weakening behavior has been observed in various rocks and gouges, and it mainly depends on the normal stress and slip velocity (Chen et al, 2017; Del Gaudio et al, 2009; Hirose & Shimamoto, 2005; Hu, Yin, et al, 2018; Mizoguchi et al, 2007; Tsutsumi & Shimamoto, 1997) or on the power density, that is, the product of normal stress and velocity (Deng et al, 2020; Di Toro et al, 2011).…”

“…If the temperature is sufficient for rock melting to occur, a molten layer can form, which may enhance the mobility of rockslides (De Blasio & Elverhøi, 2008). In carbonate rocks, calcite or dolomite decomposition may occur at high temperature, associated with a release of CO 2 that may enhance pore pressures, while nanoparticles of CaO may lubricate the shear zone (Goren et al, 2010; Hu et al, 2018, 2019; Mitchell et al, 2015). Thermal pressurization may also occur, with generation of superheated steam in water‐rich shear zones (Goren & Aharonov, 2007; Habib, 1975; He et al, 2015; Wang et al, 2018).…”

Closure to “Effect of Grain Size Distribution of Sandy Soil on Shearing Behaviors at Soil–Structure Interface” by Han-Lin Wang, Wan-Huan Zhou, Zhen-Yu Yin, and Xi-Xi Jie

“…2(a)]. This suggests that the water content is also an important influential factor to the soil-structure interface behaviors, which is probably due to the easy particle crushing under saturated state (Yin et al 2017;Hu et al 2018;Chen et al 2020a). Relatively low values can also be identified for the interface friction angle in Liang et al (2017), in which the tests were conducted on soil with a relatively high water content (20%) for sandstone and mudstone.…”