Abstract: Breakout blasting often responds 40 %－60 % fracturing soil quantitative during the course of the whole frozen soil blasting tunneling in shaft. Wide pitch-row breakout blasting can increase the effective application of free face and consolidated reflection and tensile affection of free face stress wave and cancel or reduce the decreasing field in frozen soil. Theoretical analysis and model test of binocular explosive funnel have been presented to the most important parameter, dense coefficient of borehole in breakout blasting, and the volume of explosive funnel, v, and the maximal convex capacity, h, between two boreholes after blasting also has been thought synthetically. The authors think dense coefficient of borehole, m=1.5 is reasonable. Combined with the arc layout of breakout bore of vertical well and the feature of frozen soil with relative bigger restriction effect, the dense coefficient of borehole of breakout blasting in shaft suggested should be decreased rationally based on it, which was proved in further engineering practice.

Key words: frozen soil blasting in shaft, dense coefficient of boreholes, model test, engineering application