Experimental investigation of the influence of high water pressure on dynamic strength and deformation characteristics of red sandstone

The deep rock mass is in a high water pressure and high geo-stress occurrence environment,the dynamic mechanical properties of rocks are deeply affected by the occurrence environment. In order to investigate the effects of the high water pressure and the high geo-stress on the dynamic mechanical properties of rock mass, based on a self-developed high water pressures and high geo-stress rock dynamic test device,impact tests are carried out on red sandstone samples under different water pressures and axial static stresss. The variation rules of the dynamic peak stress,the ultimate strain,the average strain rate and the dynamic deformation modulus of red sandstones under different water pressures are analyzed respectively. The relationship among the average strain rate,the dynamic peak stress and the ultimate strain are explored. Empirical models for the relationship between the water pressure and the peak stress,the ultimate strain,the average strain rate,and for the relationship between the ultimate strain and the average strain rate are constructed. The strength and deformation characteristics of the microstructure of rocks under the water pressure are analyzed based on sliding crack model and the influence mechanisms of the water pressure on the dynamic mechanical properties of rocks are explored. The results show that,under the same axial static stress,the peak stress of rock samples increases gradually with the increase of the water pressure,and the peak stress shows a good logarithmic function distribution with the water pressure. Besides,the average strain rate and the ultimate strain of rock samples both decrease exponentially with the increase in the water pressure. The Meniscus effect,the Stefan effect and the Newtonian internal friction effect of the water in the fractured surface of red sandstone and the external water pressure inhibit the initiation and expansion of the fissures,and thus improve the compressive strength and deformation resistance of red sandstone at dynamic loading level. The research results are beneficial to the perfection of deep rock dynamic theory and provide a theoretical basis for the safe and efficient design and construction of blasting excavation in rock mass engineering with deep high water pressure environment. © 2023 Academia Sinica. All rights reserved.