Abstract:

Technology of blast-induced caving roof based on the successive mining, it is said that the caving zone of fracturing are controlled through the pre-splitting blasting and inducing fracture are developed by the forced blasting. With the development and expanding of the cracks, the rock mass would have been instability and caving in the roof. But, to the process of the induction caving roof by blasting in the underground mine, the effects were invisible to the pre-splitting blasting and the forced blasting. It is difficult to quantitatively evaluate the effect of blasting. Using the borehole camera system, the technique of front view and digital panorama were used to inspect the effect of blasting. The shape of the hole-wall was detected before blasting, and the effect of the inducing fracture was inspected after blasting in the hole-wall. Especially, the cracks character was described by the digital panoramic borehole camera. The photographs were analyzed by the view and digital method. The results of the digital panoramic borehole camera show: (1) The pre-splitting cracks had been formed after pre-splitting blasting. Its width is up to 20-40 mm; and the half wall of hole could be seen in the bottom. (2) Large of secondary cracks were formed in the rock mass of roof, the crack form is “X”. And the original cracks were expanded. (3) The mass shapes of blasting was right, the rock stacked by the natural angle of slope. It is advantage to induction caving roof to the large cracks and ruptured structural rock mass.

Key words: inducing blasting, induction caving, borehole camera, visualization