Experimental study on the crack propagation rule of a new type of dual-charge and its surrounding controlled blasting
The key to the forming quality of underground metal mine roadways lies in the con-trolled blasting of peripheral holes.In this study,a new dual-shaped charge-controlled blasting technology based on the shaped charge blasting technology is proposed to improve molding quality around the roadway.The distribution law of explosive stress fields and the characteris-tics of damage distribution under the structures of ordinary charge,shaped charge,and dual-shaped charge are compared and analyzed by applying explosion mechanics,rock-fractal theory,numerical simulation,and laboratory experiments.Thereafter,the field industrial test of controlled blasting using the new dual-charge is completed.The study results indicated that the peak value of effective stress in the concentrative direction of the hole wall of dual-shaped charge blasting is 62％higher than that of the shaped charge and 1.2 times higher than that of the ordinary charge.The crack propagation length in the energy-gathering direction of the dual-shaped charge exceeds 150 mm,which is significantly larger than both the shaped charge and the ordinary charge.Additionally,the peak crack propagation velocity of dual-shaped charge blasting is 1.21 times that of the shaped charge,the stress intensity factor at the crack tip is 1.45 times that of the shaped charge,and the fractal dimension in non-convergent direction is reduced by 4％to 18.24％.The incidence of half-eye marks in the roadway section of dual-charge blasting is 38％higher than that of ordinary charge and between 10％and 25％higher than that of shaped charge.Upon adopting the new dual-shaped blasting technology,the form-ing quality around the roadway is significantly improved,and the degree of damage is reduced,showing promising engineering application prospects.
new dual-shaped chargeexplosive stress fieldexplosive fissure fieldrock fractal theoryacoustic wave testforming quality around the roadway
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