Study on Smooth-Blasting Results in Jointed and Fractured Rock

Factors that affect blasting results may be grouped into those factors that can be controlled and those that cannot be controlled. The controllable factors include explosive properties, initiation timing, and blast geometry. The uncontrollable factors comprise the rock 's natural structures, such as joints and fractures, and the properties, such as elastic constants, density and strength. Among these, the in- fluence of rock structural planes often contributes a high degree of vari ability to blasting results. This paper presents a theoretical analysis of rock structural plane influences on smooth-blasting results based on elasticity and stress wave propagation theory with an emphasis on smooth blasting techniques. Two types of simulated experiments in lab (using strain and acoustic emission measurements) are used to verify the theoretical analysis. The results show that it is difficult to achieve smooth-blasting results when the angle between the natural rock structural planes and the blast-induced fracture planes ranges from 10° to 60°. Among these angles, 30° is the least desirable angle to produce a smooth wall. For an- gles less than 10° and greater than 60°, the influence of rock structural planes on blasting results can be ignored.