Experimental and numerical study on the loading rate effect of deep CRLD anchored soft rock

The accelerated deformation effect of the surrounding rock in deep high-stress, strongly disturbed soft rock roadways is particularly pronounced, leading to frequent failures in anchoring system and surrounding rock instability. To address this issue, this paper conducts a comparative study through biaxial compression physical model experiments, examining the mechanical behavior and failure mechanisms of a novel constant-resistance large-deformation (CRLD) anchor cable and conventional high-strength (HS) anchor cable in anchoring soft rock under different loading rates. Experimental results indicate: As the loading rate increases, the peak strength, elastic modulus, and energy absorption values of both types of anchored rock gradually increase, while the residual strength shows a trend of first decreasing and then increasing. At high loading rates, the relative growth rates of mechanical parameters and energy absorption values in CRLD anchored rocks are significantly enhanced. Acoustic emission data indicate that, with increasing loading rates, the maximum count values and cumulative energy values of both types of anchored rock gradually increase, along with a relative increase in the number of high-count events. However, the overall distribution of counts in CRLD anchored rock is more uniform, the energy release process is smoother, and the acoustic emission characteristic values are significantly lower. Observations of failure characteristics reveal that, with increasing loading rates, the degree of crack development in CRLD anchored rock significantly increases, with the failure mode gradually shifting from a tensile crack-dominated to a shear crack-dominated tensile-shear mixed failure mode. Finally, based on the PFC-FLAC coupled numerical simulation method, a numerical model of CRLD anchored rock is constructed. Through statistical analysis of its mesoscopic damage evolution characteristics, the reliability of the physical model experimental results is validated.