Experimental study on rock-breaking load in slot-hydraulic blasting

Slot blasting is widely used in mining and tunnel construction, municipal demolition, water conservation, hydropower, and other related projects due to its low cost and high efficiency. In the slot-blasting technique, it is necessary to break the rock efficiently and minimize the damage to the area surrounding the rock. Therefore, improving the blasting efficiency and explosive energy utilization rate as well as reducing the blasting vibration and excessive crushing of rocks are of great significance to the development of blasting engineering. When air spaced uncoupling medium is used in slot blasting, its rock-breaking efficiency is significantly low due to various factors such as generation of shock waves, low quasi-static pressure, low energy utilization rate of explosive, and weak rock-breaking ability. To improve the rock-breaking load of slot blasting, the slot-hydraulic blasting method was proposed. In this method, water is utilized as the uncoupling medium for slot blasting as water has better microcompressibility and high energy transfer efficiency; in addition, research on its characteristics under rock-breaking load was investigated. Slot blasting with air spaced uncoupling charge and slot-hydraulic blasting tests were carried out under the independently developed slot blast load test system. The test results show that the shockwave pressure of slot-hydraulic blasting tests is approximately 35 times that of the air uncoupling blasting method because of the generation of high-pressure shockwaves and the higher incident efficiency. The hydraulic blasting quasi-static pressure is 37–46 times that of the air spaced uncoupled blasting, the quasi static pressure drop of hydraulic blasting is slow, and the pressure holding time is longer. The research results reveal that the energy utilization rate in the slot-hydraulic blasting is high and the blasting load improvement is significant. These results may help to better understand the rock-breaking load characteristics of slot-hydraulic blasting and provide theoretical and experimental support for utilizing the method in engineering applications.