Mechanistic formulation and validation of cutting seam by energy-focusing blast for pressure relief of deep roadway

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Coal sources still comprise a significant proportion of the global energy supply, especially for developing countries. As mining depth increases, roadway instability, failure, and burst become increasing concerns over deep resource utilization and mining safety. Cutting seam by energy-focusing blast (CSEFB) technique is a novel approach to mitigate the problems. Driven by the demand for further understanding and application, this study discusses the mechanistic formulation of CSEFB through theoretical analysis, numerical simulation, and field experiments. Results show that CSEFB uses the broken-expansion rock and roof-cutting effect to relieve mining stresses. The CSEFB angle and length are two critical technical parameters. The angle is the prerequisite for validating pressure relief, and the length is the condition for determining the relief degree. The formulas are given for determining the range of angle and length. Within the range, the pressure-relief effect decreases modestly with increasing angle and increases significantly with increasing length. The standard length is proposed to use the support by bulking rock fully. An increase in the length can provide an additional effect by roof cutting itself, but this effect is limited as the length increases. This mechanism helps the formulation of CSEFB in the application. A bigger angle and the standard length are primary considerations. If requiring additional pressure-relief effect, a moderate increase in the length can add to pressure-relief effect by improving the stress field. Combined numerical simulation and field experiment with a typical high-stress deep mine, CSEFB exhibits good adaptability. Apart from relieving the high vertical stress, CSEFB avoids bad influences by the great horizontal stresses. The floor heave is exploited to facilitate the pressure-relief process. Research results have importance to the CSEFB application and promotion, thus contributing to the safety of deep mining.