Development of fracture zones in rocks during camouflet blasting

A modified model to calculate the size of the crushed zone around a blast-hole

“…In the model proposed by Il'yushin (1971), the material in the crushed zone is assumed to be incompressible granular medium with cohesion. However, Il'yushin's formula is applied to limestone, talc-chlorite, and concrete, and Vovk et al (1973) noted that Il'yushin appeared to overestimate the size of crushed zone. On the other hand, in Il'yushin's formula derivation process, the gas adiabatic index in the process of blasting cavity expansion was taken as a constant, so the formula is not applicable to conditions of large decoupling ratios.…”

“…Several drilling and blasting tests reported by other researchers have been used to validate this modified model's applicability to full-scale blasting. This paper collects four sets of data from blasting tests in limestone and concrete by Vovk (1973), one set from decoupling charge drilling blasting tests in granite by Bergqvist, 1996 andOlsson et al, 2005), three sets from blasting tests in a coal mine by Slaughter (1991), one set from blasting tests in fosroc grout by La Rosa and Onederra (2001), and two sets of data from blasting tests in hard top-coal at the No.1 Honghui Mine by Suo (2004). Detailed test parameters are given in Table V. Two drilling and blasting experiments were conducted by La Rosa and Onederra (2001) to measure the size of the crushed zone from a decoupled charge, as shown in Figure 2.…”