An Experimental Study on Physical and Mechanical Properties of Fractured Sandstone Grouting Reinforcement Body Under Freeze–Thaw Cycle

Freeze–thaw cycles lead to progressive damage in macro-defects within the rock mass, compromising its structural stability and ultimately resulting in frost-induced damage in rock mass engineering. Grouting plays a critical role in reinforcing fractured rock masses and enhancing their structural integrity. Investigating the physical and mechanical properties of grouted reinforcement bodies subjected to freeze–thaw cycles is of substantial theoretical and practical importance for ensuring the safe operation of rock engineering. This study focuses on fractured sandstone grouting reinforcement bodies to evaluate the impact of freeze–thaw cycles on their microscopic pore structure and macroscopic mechanical properties. Nuclear magnetic resonance (NMR) T2 spectra demonstrate that freeze–thaw cycles progressively enlarge internal pores within the grouted reinforcement body, with pore characteristics evolving from micropores to mesopores and from mesopores to macropores. Triaxial compression test results indicate that as the number of freeze–thaw cycles increases, the peak strength, elastic modulus, cohesion, and internal friction angle of the grouted reinforcement body decrease, with both peak strength and elastic modulus following an exponential decline relative to the number of cycles. Furthermore, the crack dip angle and confining pressure exert significant influence on the failure mode of the grouted reinforcement body.