Dynamic tensile mechanical properties of water-saturated and frozen sandstone after freeze-thaw fatigue damage treatment

Abstract

To study the physical properties and dynamic mechanical response characteristics of rock materials in seasonally frozen regions, density, P-wave velocity, nuclear magnetic resonance, and dynamics Brazilian disc tests were carried out on sandstones treated with different numbers of freeze-thaw cycles. The experimental results show that the water-saturated density and P-wave velocity of sandstone decrease and the Nuclear magnetic resonance porosity increases as the number of freeze-thaw cycles increases. Under a certain loading rate, the dynamic tensile strength of water-saturated sandstone gradually decreases and that of frozen sandstone gradually increases as the number of freeze-thaw cycles increases; at the same time, the dynamic tensile strength of both water-saturated and frozen sandstone increases as the loading rate increases under the same number of freeze-thaw cycles. The reason for the variability of dynamic tensile strength between water-saturated and frozen sandstones with the increase in the number of freeze-thaw cycles can be attributed to the change in porosity. On this basis, the concept of relative dynamic tensile strength of sandstones was introduced and regression analysis was carried out with the increase ratio of porosity, and it was found that the correlation between the relative dynamic tensile strength and the increase ratio of porosity was strong. The relative dynamic tensile strength of water-saturated sandstone decreases exponentially with the increase ratio of porosity; the relative dynamic tensile strength of frozen sandstone increases exponentially with the increase ratio of porosity.

Keywords

• Freeze-thaw cycles
• Rock dynamic mechanics
• Dynamic tensile strength
• Nuclear magnetic resonance test
• Strength evolution model