Fracture propagation mechanism and CO2+O2 in-Situ leaching effect of low-permeability sandstone-type uranium deposits under millisecond blasting

Aiming at the key problems such as poor permeability and low leaching rate in the in-situ leaching (ISL) of low-permeability sandstone-type uranium deposits, this study investigates the fracture propagation mechanism of the rock mass and predicts the mining performance of CO 2 +O 2 ISL. Taking a Xinjiang low-permeability sandstone-type uranium deposit as the research object, a field-scale "six injection and two extraction" well group model was built via LS-DYNA with RHT and HJC constitutive models, and two initiation modes (sequential hole initiation and interval initiation) were designed. By analyzing the evolution laws of kinetic energy, internal energy, elastic displacement, and elastic displacement loading rate, the propagation and distribution characteristics of fractures are investigated, a reaction-flow model for fractured uranium deposits is established, and numerical simulations of ISL under different blasting parameters are carried out. The results show that the maximum radius of the crushing zone decreases with the increase of initiation interval, while the peaks of fracture zone radius occur at 20 ms with optimal connectivity. This millisecond blasting reduces leaching dead zones, and the leaching efficiency is increased by 6.14 % compared with the 5 ms interval. This study optimizes ISL mining parameters and provides theoretical support for efficient deposit exploitation.