A Comparison of Mechanical Properties and Failure Processes of Saturated and Unsaturated Slate from Sichuan-Tibet Plateau Area, China

Abstract

Water content significantly affects the physical and mechanical properties of rock and can cause rock mass to become unstable. This, in turn, can cause geologic disasters such as water inrush and surrounding rock deformation. Uniaxial compression experiments on slate samples drilled from the surrounding rock of a tunnel in the Chinese Sichuan-Tibet Plateau area were performed coupled with acoustic emission (AE) monitoring. The changes in mechanical properties and failure processes of unsaturated and saturated slates were investigated comparatively through test results. Phenomena of a slight drop of σ1 in the compaction and elasticity stage were observed, and it is due to the sliding of slate along the layered surface. According to the results, the average compressive strength of saturated slates was reduced by 24.3% compared to the unsaturated slates. The spatiotemporal evolution characteristics of AE indicated that the deformation and fracturing of unsaturated slates happened concentratedly and violently in the accelerated crack growth stage, while that of saturated slates occurred with low energy and uniform distribution spatially and temporally in the whole process. Moreover, water content reduced the brittleness index of unsaturated slate by 17.1%. For both conditions, the abundance of AE activity before failure shifted from a high level to a low level and lasted until failure. This can be used as a preliminary failure prediction of slates.

Influence of Rock Weathering and Saturation on Compressive Strength and Slope Stability: A Uniaxial Test Analysis

“…The porosity value significantly influences rocks' uniaxial compressive strength values due to the reaction between rock mineral grains [9]. The strength of the rock binding force affects the compactness between rock grains; if the binding force is strong, it produces a hard rock with a high uniaxial compressive strength value, and vice versa, if the binding force between the grains is weak, it produces a rock that is less compact and forms many pores filled with water or air, so that the uniaxial compressive strength value is low.…”

“…Several researchers have concluded that water content significantly impacts changes in the structure and characteristics of rocks [9], so the strength of various rocks due to saturation can be reduced by up to 90%. Rock strength increases when saturation is low and decreases significantly when saturation is high [10].…”

“…Zhou et al [11] observed the uneven water distribution on the soaked cylindrical sandstone specimens; the rock strength is greatly reduced even when the water content is less than 3.51%. Zheng et al [9] researched saturated and unsaturated limestone, which were comparatively investigated through compressive strength test results. The average compressive strength of the saturated limestone was reduced by 24.3% compared to the unsaturated limestone.…”

Influences of Water Content on Acousto-Mechanical Properties and Failure Behaviors of Triaxially Compressed Shale

“…The experimental results showed that the peak strength and elastic modulus of saturated granite are lower than those of dry granite. The softening effect of water content on the strength of slate was further investigated via indoor experiments (Zhang et al [12], Lv [13], Chen et al [14]), and their results showed that the water content can weaken the mechanical properties of slate. Cai et al [15] found that the calcite cementation between particles gradually dissolved and the density and width of intergranular cracks increased after the dry-wet cycle, which may be the reason for the deterioration of the mechanical properties of sandstone.…”