Triaxial Loading and Unloading Tests on Dry and Saturated Sandstone Specimens

Abstract

The brittle failure of hard rock due to the excavation unloading in deep rock engineering often causes serious problems in mining and tunneling engineering, and the failure process is always affected by groundwater. In order to investigate the effects of stress paths and water conditions on the mechanical properties and failure behavior of rocks, a series of triaxial compression tests were conducted on dry and saturated sandstones under various loading and unloading paths. It was found that when the sandstone rock samples are saturated by water, the cohesion, the internal friction angle and the Young’s modulus will decrease but the Poisson′s ratio will increase. The fracturing characteristics of the sandstone specimens are related to the initial confining pressure, the stress paths and the water conditions from both macroscopic and microscopic viewpoints. The failure of sandstone in unloading test is more severe than that under loading test, particularly for dry sandstone samples. In unloading test, the energy is mainly consumed for the circumferential deformation and converted into kinetic energy for the rock bursts. The sandstone is more prone to produce internal cracks under the effect of water, and the absorbed energy mainly contributes to the damage of rock. It indicates that the possibility of rockburst in saturated rock is lower than the samples in dry condition. It is important to mention that water injection in rock is an effective way to prevent rockburst in deep rock engineering.

Impact of water on peak and residual shear strength parameters and triaxial deformability of high-porosity building calcarenite stones: Interconnection with their physical and petrological characteristics

“…In this line, Morrow et al [77] reported that the coefficients of friction dropped 20-60% with the addition of water for clay minerals which can take large amounts of interlayer water. Furthermore, these results are in agreement with the experimental data obtained by Li et al [78], who reported that both cpeak and ϕpeak values of saturated sandstones are lower than those of dry sandstones. Additionally, in other stone types, such as granites or meta-sedimentary rock materials, important decreases of ϕpeak due to water saturation have also been found [29], [76].…”

Special Issue on Fatigue and Fracture of Non-Metallic Materials and Structures

“…Impact behavior is studied with reference to laminate composites [20,21]. Other papers devoted to rocks concern their cutting resistance [22] and their multiaxial response under dry and saturated conditions [23]. Finally, the mechanical behavior of a monomer structural component is studied in [24].…”

Effect of Physical Properties on Mechanical Behaviors of Sandstone under Uniaxial and Triaxial Compressions

“…The water weakening effect can be problematic for the stability of rock structures due to interactions between water and silicate minerals. Water weakens the hydrogen bonds, promotes the dissolution of clay minerals, and creates voids that can change the rock microstructure and ultimately weakens the rock [ 5 , 6 , 7 , 8 , 9 , 10 ]. In addition, pores inside a rock matrix act as flaws that create stress concentration and lead to macroscopic failure [ 11 ].…”

“…The triaxial compressive strength of sandstone is affected by several factors, such as water content, confining stress, and porosity. Triaxial compression test results revealed a positive effect of confinement on compressive strength [ 1 , 7 , 18 , 19 , 20 ]. The influence of confining stress on the triaxial compressive strength of sandstone has been a subject of earlier investigations.…”