Effect of water content on the mechanical properties and deformation characteristics of the clay-bearing red sandstone

Abstract

The presence of water has a great influence on the strength and deformation of clay-bearing sandstone. Most of the natural rocks suffer water softening of different saturations. In this study, due to the importance of the clay-bearing rocks in geoengineering practice, red sandstone was chosen to investigate the effect of water contents on the UCS (uniaxial compressive strength), TCS (triaxial compressive strength), BTS (Brazilian tensile strength), PLS (point load strength), and DSS (direct shear strength). The UCS and TCS are linearly decreased as the water saturation increases. When the water saturation increases from 0 to 100%, the UCS and TCS have decreased by about 52.8% and 29.3%, respectively. The BTS, PLS, and DSS are exponentially decreased with increasing water saturation, which have a reduction of about 45.5%, 66.3%, and 49%, respectively. Four typical deformation stages are observed during compression for this red sandstone samples, including an obvious compaction stage. The water saturation does not have any effect on the ratio of the strain on the transition points of these stages to the peak strain, as well as the stress. Besides, a rapid increase of the AE count occurs at the plastic yield point although the cumulative AE count has an obvious decrease trend with increasing the water saturation. Then, considering the effect of water saturation, a complete constitutive model has been proposed to well predict the stress-strain relationship of the red sandstone. The water’s weakening effect on the clay-bearing red sandstone has also been deeply discussed and developed.