Experimental Investigation on Influencing Factors of Rock Fragmentation Induced by Carbon Dioxide Phase Transition Fracturing

Abstract

Carbon dioxide phase transition fracturing is a novel physical blasting technique, which is gradually used in mining and underground space engineering. The improvement of its rock breaking efficiency is the key concern in the application. In this paper, field experiments of CO2 phase transition fracturing were conducted. Based on the strain monitoring and fracturing crater volume measuring, the variation of CO2 filling amount and shear sheet thickness on rock fragmentation of CO2 phase transition fracturing was investigated. The experimental results indicated that the fracturing crater is shaped as an elliptical cone that is longer in the jet direction and shorter in the vertical jet direction. With the increase of the CO2 filling amount, the excavated crater volume gradually increases, but the growth rate gradually decreases. The powder factor is constant within a certain charge amount, and after exceeding this charge amount, the powder factor of CO2 increases significantly. As the shear sheet thickness increases, although the consultant peak stress gradually increases, its growth rate is still unchanged. The crater volume and its growth rate gradually increase in the same situation. Moreover, with the shear sheet thickness increase, the CO2 powder factor decreases continuously, and the decline rate remains unchanged.

Decay Law of Supercritical CO2 Phase Transition-Induced Shock Waves in Rocky Media

“…To veri sion, the experimental results are compared with the shear sheet damage e ure 5. As can be seen from Figure 5, the experimental results are similar to those of previous studies [13,14], and the shear damage equation fits the experimental test shock wave peak pressure well. Therefore, the shear damage formula can replace the supercritical CO 2 phase Symmetry 2023, 15, 1802 7 of 13 transition shock pressure in Equation (10) for calculation.…”

“…Existing views are generally that the supercritical CO 2 phase change rock breaking project concerning rock fragmentation is essentially the result of a shock wave and highenergy gases working together [12]. In the CO 2 phase change blasting process, a shear blade rupture CO 2 high-pressure gas shock wave is formed, and the initial peak shock pressure size and CO 2 charge and shear blade thickness are highly correlated, of which the thickness of the shear blade is the main control variable [13,14]. After the high-pressure gas impacts the rock body, incident rock body stress is formed, which is greater than the rock body rupture pressure, and the rock body becomes damaged.…”

Experimental study of precursory features of CO2 blasting-induced coal rock fracture based on grayscale and texture analysis

“…Cai et al [21] studied the influence of coal seam joints on crack morphology and perforation damage under SC-CO 2 fracturing, and analyzed the stress-strain characteristics, internal crack propagation, and macroscopic crack failure modes of sandstone through experimental research on the relationship between flow field and strain change [22]. Gao et al [23] studied the influence of CO 2 initiation pressure and shear plate thickness on CO 2 phase change fracturing and rock breaking process based on strain monitoring and fracturing pit volume measurement. Shang et al [24] conducted CO 2 blasting experiments under true triaxial stress, and obtained the crack propagation law through monitoring the surface strain of the specimen.…”