Case Study on Pre-Splitting Blasting Reasonable Parameters of Goaf-Side Entry Retained by Roof Cutting for Hard Main Roof

The key parameters of pressure relief pre-splitting blasting technology (PRPBT) contribute to the implementation effect goaf-side entry by roof cutting (GSERC). This study is an attempt design including height, angle, spacing between boreholes, charge structure and sealing length using theoretical analysis, numerical simulation field implementation. basic quality index main 666.27, combined with peeping observation result, belongs category a hard roof. Different from weakened compound roof, unreasonable PRPBT for lead three problems insufficient effect, suspension in goaf serious damage rock mass rib. closely related parameters, parameters. Hence, solve those problems, new strategy was proposed based on optimized directions increasing decreasing changing adjusting length. According results calculation, situ measurement, spaced distance were determined as 10 m, 15°, 500 mm, 4 + 3 2 2.4 respectively. fissure rate assess developed different schemes. achieved better entry, eliminated goaf. this could other similar coal mines under condition