Distribution characteristic of breaking extending area of weakening-blast in hard top-coal

Based on the rock blast theory, combined with the data of the weakening-blast testing in hard coal body and big coal sample blast experiment, the distribution characteristic of the breaking area of the weakening-blast in hard top-coal was analyzed, and the calculation method on the breaking area section radii of the weakening-blast in hard top-coal was presented.The autopic results indicate that the breaking extending area of the weakening-blast in hard top-coal can be divided into the three areas of the crush area, the much-crack area and the crack area.