Effect of Specimen Placement on Model Rock Blasting

Abstract

AbstractSmall-scale model blasting plays an important role in understanding mechanism of rock fragmentation by blasting and improving blast technology in rock and mining engineering. Because a specimen (or model) often needs to be placed on either a ground or another material in model blasting, an additional interface appears between the specimen and the ground (or material), compared with an engineering blast that does not have such an interface. In this paper, four model blasts with high-speed photography were presented. The results showed that: (1) as the impedance of a rock specimen was smaller than that of the ground material, the specimen was thrown up and a certain amount of kinetic energy was brought with such a bounce. Thus, this placement should be avoided in model blasts. (2) As a rock specimen was placed on three blocks of the same type of rock as the specimen the specimen was not bounced up during blasting. Correspondingly, no kinetic energy was induced by specimen bounce. Therefore, this placement is recommended for model blasting. If very high specific charge must be used in model blasting, the above-recommended method will not work well due to possible breakage of the base material during blasting. In this case, the rock specimen can be placed on a material with smaller impedance than that of the rock specimen so that specimen bounce can be reduced. Accordingly, such a possible specimen bounce should be estimated by stress wave analysis.