Effects of humidity and interlayer cations on the frictional strength of montmorillonite

Abstract

We developed a humidity control system in a biaxial friction testing machine to investigate the effect of relative humidity and interlayer cations on the frictional strength of montmorillonite. We carried out the frictional experiments on Na-and Ca-montmorillonite under controlled relative humidities (ca. 10, 30, 50, 70, and 90%) and at a constant temperature (95 °C). Our experimental results show that frictional strengths of both Na-and Ca-montmorillonite decrease systematically with increasing relative humidity. The friction coefficients of Na-montmorillonite decrease from 0.33 (at relative humidity of 10%) to 0.06 (at relative humidity of 93%) and those of Ca-montmorillonite decrease from 0.22 (at relative humidity of 11%) to 0.04 (at relative humidity of 91%). Our results also show that the frictional strength of Na-montmorillonite is higher than that of Ca-montmorillonite at a given relative humidity. These results reveal that the frictional strength of montmorillonite is sensitive to hydration state and interlayer cation species, suggesting that the strength of faults containing these clay minerals depends on the physical and chemical environment.

Modelling Hydration Swelling and Weakening of Montmorillonite Particles in Mudstone

“…Therefore, the water swelling law of the integrated montmorillonite matrix in mudstone can be indirectly characterised by determining the water content within it. density versus water content ( Figure 14) and compared with data calculated by Equation (2). The experimental results were found to be in good agreement with the calculated results for the hydration swelling model obtained above; therefore, its rationality was verified.…”

“…It is considered that the fitting equation (Equation 2) accurately describes the hydration swelling of integrated specimens with a goodness of fit of 0.96, and this accurately reflects the hydration swelling properties of integrated specimens: The relationship between the average density and w was linearly fitted and is shown in Figure 13. It is considered that the fitting equation (Equation 2) accurately describes the hydration swelling of integrated specimens with a goodness of fit of 0.96, and this accurately reflects the hydration swelling properties of integrated specimens: All the densities of integrated specimens obtained earlier were plotted within the space of density versus water content ( Figure 14) and compared with data calculated by Equation (2). The experimental results were found to be in good agreement with the calculated results for the hydration swelling model obtained above; therefore, its rationality was verified.…”

“…Advances made to understand the behaviour of mudstone over the last 50 years have shown the importance of the role of clay mineral components when modelling its behaviour. In the field of geotechnical and hydraulic engineering, soil and rock comprised of montmorillonite have an adverse effect on the stability of engineering structures owing to the layered molecular structure of montmorillonite and its hydration swelling and weakening properties [1][2][3].…”

What is the origin of macroscopic friction?

“…Double-direct shear tests of the cleavage planes of mica on two sliding planes were performed as in our previous studies ( 14 , 15 ) (Fig. 3A).…”

Sensitivity of elastic thickness to water in the Martian lithosphere

“…where μ is the frictional coefficient and C is the frictional cohesive strength. Frictional coefficients are similar for most investigated minerals (μ = 0.6-0.85; Byerlee 1978); however, recent laboratory data have shown that several clay minerals yield much lower coefficients (μ~0.1; Morrow et al 2000;Tetsuka et al 2018). In the present study, we used Byerlee's law to calculate the mechanical strength in the regions undergoing brittle deformation, but we also discuss the effect of clay minerals that reduce brittle strength at wet environment.…”