Experimental Study on High‐Pressure Air Blasting Fracture for Coal and Rock Mass

Abstract

In order to research on the issue of high-pressure gas blasting fracture deeply, a high-pressure gas blasting cracking experimental system was established; the effects of gas pressure and gas volume on the morphology of crack growth were studied; the p-t curve of pressure in the blasting process with time was obtained; and the mechanism of high-pressure gas blasting cracking was analyzed in this paper. The conclusion has shown that the stage of effect of high-pressure gas blasting on the test block includes three stages: the gas jet impact stage, the crack initiation and development stage, and the perforation fracture stage. In the design of gas pressure of 5 MPa, the experimental block only produces one longitudinal main crack. As the gas pressure increases to 7.5 MPa and 10 MPa, besides forming one longitudinal main crack, a transverse main crack is formed with further expanded 4–6 secondary cracks. In the same design of gas pressure regardless of volume size, each pressure variation stage has the same length, and the experimental block of the cracking pressure is basically the same. With the higher design pressure, the cracking pressure and the fracture pressure are higher. In the same design of gas pressure, with the larger gas volume, the fracture pressure required for the experimental block is smaller.

Comparative Experimental Study of Fracture Mechanisms and Characteristics of Coal-like Materials under Quasi-Static and High-Pressure Air Blasting Fracturing

“…To gain insight into the fracturing process of air blasting fracturing at different blast pressures, Gao et al monitor the instantaneous pressure−time curve with different blast pressure and demonstrated that the initial fracture pressure increased with the increase of blast pressure, but failed to conduct an in-depth analysis of the fracturing mechanism of different air blasting fracturing. 28 In summary, previous studies have primarily focused on the characterization of fracturing mechanisms of various air fracturing technologies, without comparing air quasi-static fracturing and air blasting under consistent conditions. As a result, the mechanism transformation of air fracturing technology under different loading rates cannot be thoroughly analyzed, impeding the provision of a theoretical basis for parameter optimization of air fracturing technology in coal seam fracturing applications.…”

“…They found that the peak strain was negatively correlated with the distance from the blast hole, which increased and then decreased with the number of cyclic impacts. , Nevertheless, none of the aforementioned studies have compared the mechanism and effectiveness of air blasting through experiments with varying blast pressure. To gain insight into the fracturing process of air blasting fracturing at different blast pressures, Gao et al monitor the instantaneous pressure–time curve with different blast pressure and demonstrated that the initial fracture pressure increased with the increase of blast pressure, but failed to conduct an in-depth analysis of the fracturing mechanism of different air blasting fracturing . In summary, previous studies have primarily focused on the characterization of fracturing mechanisms of various air fracturing technologies, without comparing air quasi-static fracturing and air blasting under consistent conditions.…”