Experimental Study on Tensile Characteristics of Layered Carbonaceous Slate Subject to Water–Rock Interaction and Weathering

Abstract

The transverse isotropy of rock masses formed by sedimentation is a common stratum environment in engineering, and the physical–mechanical properties can degrade due to water–rock interaction (WRI) and natural weathering, which potentially lead to the instability or collapse of tunneling, slopes and mining. Taking the carbonaceous slate of the Muzhailing tunnel as the research object, two types of specimens, which include oven-drying (instant drying in oven after fabrication) and natural air-drying (static weathering for 60 days after fabrication) were prepared, respectively, after which Brazilian tests were carried out and the tensile properties were analyzed under the two conditions. The experimental results showed that the two kinds of carbonaceous slate all show brittle failure, but the mechanical response such as failure displacement and peak load is obviously different. The tensile strength of the specimens is significantly all affected by the bedding, while the cleavage failure patterns of the two kinds are affected to different degrees. The softening coefficient of the natural air-drying specimen is 0.11–0.13, which implies that WRI and natural weathering play a vital role in the course of rock failure but have little influence on the transverse isotropy tensile property of bedding. Moreover, the mechanisms of specimen failure subject to WRI and 60 days’ weathering were explained by the SEM technique, which analyzed the micro-components and observes the process of specimen deterioration due to physicochemical reaction, the gradual development of cracks and erosion by weathering.

Study on the Degradation Effect of Carbonaceous Shale under the Coupling Effect of Chemical Erosion and High Temperature

“…The research on carbonaceous shale can be mainly divided into experimental research, numerical simulation, and theoretical derivation [10]. In terms of experimental research, Li et al [11] carried out Brazilian splitting tests on carbonaceous shale after instant drying and static weathering, and analyzed the tensile mechanical properties of carbonaceous shale with different bedding angles under the two test methods. Xie et al [12] used a scanning electron microscope-energy dispersive spectrometer (SEM-EDS) and an X-ray diffraction (XRD) to characterize the microstructure and mineral composition of carbonaceous shale, carried out uniaxial compression tests on carbonaceous shale with different water contents, analyzed its stress-strain relationship, deformation characteristics, and failure mode, and discussed the influence mechanism of water content on its mechanical properties.…”

Stability Analysis of Strongly Weathered Muddy Slate Slopes Considering Softening Conditions of Water Immersion

“…The rock mass of natural rock slopes contains many discontinuous structural surfaces [1,2]. Numerous structural surfaces disrupt the continuity and integrity of the rock mass, giving it a strong anisotropic characteristic [3].…”