Abstract
Carbon dioxide phase transition fracturing has been widely used in rock mass excavation under complex environments, and its special rock breaking process shows obvious gathering energy effect. In this paper, the gathering energy effect of this technology is considered and then the impact reduction coefficient is defined and determined. Eventually, a combined method of field tests and numerical simulations is used to study the crack propagation characteristics and spatiotemporal changes of dynamic response. The results show that the cracks grow more and more slowly as time goes by; the peak displacement and peak point velocity in the primary impact direction are both greater than those in the secondary impact direction. The peak point velocity in different directions decreases as the distance from borehole increases and it decays more and more slowly. With the increase of distance from the borehole, the peak effective stress in the primary impact direction constantly decreases. However, it increases first and then decreases in the secondary impact direction. The results mentioned above can provide effective guidance for later experimental research and engineering.
Highlights
With the continuous progress of underground space technology, the requirements for construction safety and environmental safety are becoming stricter
We fully considered the load of the borehole wall which did not correspond to the gas outlet, gas outlet, defined the impact reduction coefficient, took the crack length as the comparison standard, defined the impact reduction coefficient, took the crack length as the comparison standard, and determined and determined the most reasonable impact reduction coefficient by combining field tests and the most reasonable impact reduction coefficient by combining field tests and numerical simulation results
In order to provide the experimental basis for numerical simulation, we conducted multiple single-hole fracturing tests to obtain the rock breaking effect of Carbon dioxide phase transition fracturing (CDPTF) in actual engineering
Summary
With the continuous progress of underground space technology, the requirements for construction safety and environmental safety are becoming stricter. Carbon dioxide phase transition fracturing (CDPTF) is extensively used as an alternative to explosive blasting when performing the gas drainage in a coal mine or excavating rock mass in sensitive areas such as hospitals, residential areas, schools and gas stations [1,2,3,4,5,6] This technology utilizes the phase energy difference of the carbon dioxide phase physical transformation process to break the rock. We fully considered the load of the borehole wall which did not correspond to the gas outlet, gas outlet, defined the impact reduction coefficient, took the crack length as the comparison standard, defined the impact reduction coefficient, took the crack length as the comparison standard, and determined and determined the most reasonable impact reduction coefficient by combining field tests and the most reasonable impact reduction coefficient by combining field tests and numerical simulation results.
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