Dynamic mechanical properties and damage mechanism of sandstone under acidification condition: Application for the enhanced in-situ leaching of low-permeability sandstone uranium deposit

Abstract

During the in-situ leach mining field, blasting and acidification methods are effective to improve the permeability of uranium reservoirs. To expound the synergy effect of the two methods, the dynamic mechanical properties and damage mechanism of sandstone under acidification conditions were analyzed based on the acidification experiment and Hopkinson pressure bar experiment. Research shows that the total pore volume is largely improved with the increase of acidification reaction time from 0 d to 75 d with a maximum percentage increase of 67.57 %, which shows that the acidification reaction causes nonnegligible chemical damage. However, pores with different pore sizes are affected variously, 100-1000 nm and 1000-10000 nm pores are the dominant structure inducing the chemical damage. With the increase of the acidification reaction time, the dynamic peak strength and the dynamic elastic modulus are reduced, while the dynamic peak strain and strain rate are promoted. There exists the logistic expression and the linear expression between the dynamic peak strength and the dynamic elastic modulus with the acidification reaction time respectively, and the exponential expressions are appropriate to characterize the relationships between the dynamic peak strain and strain rate with the acidification reaction time. This study demonstrates the good potential reservoir stimulation and permeability enhancement effects uniting the blasting-enhanced permeability and acidizing-enhanced permeability methods, which can provide a theoretical reference for the reservoir stimulation of low-permeability sandstone uranium deposits.