Theoretical calculation methods generally exaggerate the extent of the EDZ and used formulas do not apply to most rock types. This study comprises of correlating the theoretical to the realized extend of the EDZ on drill and blast (D&B) excavation surface. Generally when excavation is designed, applied theoretical EDZ extend origins from explosive manufactures material to fulfill the EDZ requirements of the blasted surface. Well known theories and formulas have been used to calculate the failure of the rock.
In this work actual EDZ extend was defined and correlated to the theoretical extend when using Kemiitti 810 bulk emulsion explosive. The results were compared to realization using nitroglycerin based pipe charge F-pipe 17 × 500. All together 20 m of tunnel was excavated in crystalline granodiorite in Tampere test mine and numbers of small granite blocks were blasted in Kuru dimensional stone quarry. Realized EDZ extend definition was done visually on core samples and saw cut surfaces. Definition of theoretical EDZ extend requires rock mechanical testing of the site rock as well as borehole pressure data on used charges. Required and laboratory defined rock mechanical measures were the unconfined compressive strength, dynamic Young's modulus and Poisson's ratio. Also borehole pressure was defined in series of tests. Measured pressure values were compared to the calculated values based on ideal detonation, though it is known that in commercial explosives detonation is nonideal. The larger the charge diameter is, the more ideal explosion comes. When calculated borehole pressures were compared to the measured values it was noticed that the constant applied in the formula should vary along the charge diameter. Revised formula demonstrates how the EDZ extend can be calculated in crystalline rock when using explosives charges less than 600 g/m. The result is more realistic EDZ extend values.
