Test of a liquid directional roof-cutting technology for pressure-relief entry retaining mining

Abstract

To solve the problems in blasting roof-cutting related to pressure-relief entry retaining mining, a liquid directional roof-cutting technology is proposed in this article. To verify the adaptability of liquid directional roof-cutting technology in the practice of pressure-relief entry retaining mining, a lab cutting test was performed. The effects of the four main cutting parameters (type of abrasive, pump station pressure, speed of cutting head, nozzle diameter) on cutting capacity were examined through the test, and the optimal cutting parameters that meet the design requirements were ultimately identified. Based on the above test parameters, field engineering test equipment was developed. The results of a hole mouth cutting test and single-hole unilateral cutting test show that the liquid directional roof-cutting technology can be used to complete field cutting work, and the cutting depth and directional function can meet the design requirements. However, some new problems were found in the field application. For example, in the process of multihole bilateral cutting, the rock mass between four holes cannot form a cut-through face. However, these problems can be addressed by increasing the cutting capacity and optimizing the seam direction. In summary, the design idea of conducting roof directional cutting by using liquid directional cutting technology is viable, and the proposed technology is expected to replace blasting work in several engineering applications requiring pressure relief, such as impact pressure control and coal and gas outburst control.