The influence of immersed water level on the short- and long-term mechanical behavior of sandstone

Water has a significant effect on the mechanical behavior of rocks. A deep understanding of how water can affect the short- and long-term mechanical behavior of rock is important when assessing the stability of geotechnical projects. This study mainly focused on the effects of different soaking heights and water distributions on the short- and long-term mechanical behavior of rocks. Uniaxial compressive strength (UCS) testing and creep experiments were carried out on specimens with different water contents. The specimens of each water content were obtained by partial presoaking in water at different heights (i.e., 1/8, 1/4 and 1/2 of the height of the specimen) for 10 h and complete presoaking in water for different durations (i.e., 0.16, 0.29 and 0.97 h). The uniaxial compressive testing results show that the UCS and elastic modulus of the completely presoaked specimens exponentially decreased with increasing water content, while those of the partially presoaked specimens linearly decreased in two stages. At the same water contents, the UCS and elastic modulus of the partially presoaked specimens were lower than those of the completely presoaked specimens. In addition, the completely presoaked specimens showed mixed splitting-shear failure, while the partially presoaked specimens mainly exhibited splitting failure, which was attributed to the different water distributions in those two types of specimens. Our creep experiments show that as the water content increased, the time-to-failure decreased, while the minimum strain rate increased for both the partially and completely presoaked specimens. In addition, the time-to-failure and the duration of the accelerated creep stage of the partially presoaked specimens were both shorter than those of the completely presoaked specimens with the same water contents.

Automated summary

Water significantly affects the mechanical behavior of rocks, resulting in a decrease in uniaxial compressive strength and elastic modulus of specimens. Partially presoaked specimens exhibit a two-stage linear decrease, while completely presoaked specimens show an exponential decrease. Completely presoaked specimens exhibit mixed splitting-shear failure, while partially presoaked specimens mainly exhibit splitting failure.