Abstract
In order to determine the applicability of liquid CO2 phase-transition fracturing technology in rock mass excavations, the principles of CO2 phase-transition fracturing were analyzed, and field tests of liquid CO2 phase-transition fracturing were performed. An “Unmanned Aerial Vehicle (UAV) camera shooting + Microstructure Image Processing System (MIPS) analyzing” method was used to acquire the rock mass characteristics. Further, the Hilbert–Huang Transform (HHT) energy analysis principle was adopted to analyze the characteristics of fracturing vibration waves. The experimental results showed that during the process of fracturing, there were both dynamic actions of rock breakage due to excitation stress wave impacts, and quasi-static actions of rock breakage caused by gasification expansion wedges. In semi-infinite spaces, rock-breakage zones can mainly be divided into crushing zones, fracture zones, and vibration zones. At the same time, under ideal fracturing effects and large volumes, the fracturing granularity will be in accordance with the fractal laws. For example, the larger the fractal dimensions, the higher the proportion of small fragments, and vice versa. Moreover, the vibration waves of the liquid CO2 phase-transition fracturing have short durations, fast attenuation, and fewer high-frequency components. The dominant frequency band of energy will range between 0 and 20 Hz. The liquid CO2 phase-transition fracturing technology has been observed to overcome the shortcomings of traditional explosive blasting methods and can be applied to a variety of rock types. It is a safe and efficient method for rock-breaking excavations; therefore, the above technology effectively provides a new method for the follow-up of similar engineering practices.
Highlights
Introduction published maps and institutional affilAt the present time, the excavations of rock masses under general conditions are still mainly dependent on explosive blasting methods; due to the high safety risks and severe environmental impacts of explosive blasting, the management, and control of such explosives have become much stricter [1]
Y-direction ing to the Hilbert energy spectrum, there were many low-frequency components in the Ydirection ofofvibration the attention paid of the three directions;,attention beshould paid tobe monitoring this in direction thethree threevibration vibrationdirections; directions;,should attention should be paidtotomonitormonitoring this in subsequent applications of liquid phase-transition fracturing subsequent applicationsapplications of liquid COof fracturing technology
It was confirmed in this study that liquid CO2 phase-transition fracturing technology could be applied in surface rock excavation and will provide a new idea for the follow-up activities of similar engineering construction projects
Summary
CO2 fracturing was mainly composed of a riser, firing of a riser, firing. CO2 fracturing device was mainly composed head, heater, fracturing tube, fracturing constant pressure shear sheet, andshear energy releaser. The head, heater, tube, constant pressure sheet, and [22]. The fracturing tube is used for filling liquid carbon dioxide The fracturing tube is used for filling liquid carbon dioxide (CO2 ) of 0.5–2 pending on the application purpose. The heater is sealed in the tube for heating, on the application purpose. The heater is sealed in the tube for heating, which which is turningisliquid. Stant pressure shear sheet hassheet controlled the fracturing pressurepressure varyingvarying from 60from to 60 to 270 Mpa pressure shear has controlled the fracturing depending rockmechanical mass mechanical properties.
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