Numerical modeling of presplitting controlled method in continuum rock masses
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ORIGINAL PAPER
Numerical modeling of presplitting controlled method in continuum rock masses Z. Aliabadian & M. Sharafisafa
Received: 17 April 2013 / Accepted: 14 October 2013 # Saudi Society for Geosciences 2013
Abstract Controlled blasting techniques are used to control overbreak and to aid in the stability of the remaining rock formation. The less competent the rock mass itself, the more care has to be taken in avoiding damage. Presplitting is one of the most common methods which is used in many open pit minings and surface blast designs. The purpose of presplitting is to form a fracture plane across which the radial cracks from the production blast cannot travel. Presplitting should be thought of as a protective measure to keep the final wall from being damaged by the production blasting. The purpose of this study is to investigate the effect of presplitting on generation of a smooth wall in a rock domain under blast process in continuum rock mess. The 2D distinct element code was used to simulate the presplitting in a rock slope (open pit mining). The blast load history was applied as a function of time to inner wall of each blasthole. Important parameters that were considered in the analysis were stress tensor and fracturing pattern. The blast loading magnitude and blasthole spacing were found to be very significant in the final results. Keywords Controlled blasting . Presplitting Method . Continuum rock masses . Stress tensor
Introduction Drilling and blasting continues to be an important method of block production and block splitting. Drill and blast technique has a disadvantage that sometimes it produces cracks in uncontrolled manner and also produces micro cracks in the block as well as in remaining rock, if not carefully carried out. Z. Aliabadian (*) : M. Sharafisafa Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran, Iran e-mail: [email protected]
Recovery by this method is low as compared to other methods. Therefore, attempts have been made to develop controlled growth of crack in the desired directions. The control of fractures in undamaged brittle materials is of considerable interest in several practical applications including rock fragmentation and overbreak control in mining (Fourney et al. 1975; Fourney 1993; Kaneko et al. 1995). One way of achieving controlled crack growth along specific directions and inhibiting growth along other directions is to generate stress concentrations along those preferred directions. Several researchers have suggested a number of methods for achieving fracture plane control by means of blasting. Fourney et al. (1978) suggested a blasting method which utilizes a ligamented (continuous) split-tube charge holder. Nakagawa et al. (1982) examined the effectiveness of the guide hole technique by model experiments using acrylic resin plates and concrete blocks having a charge hole and circular guide holes. Katsuyama et al. (1983) suggested a controlled blasting method using a sleeve with slits in a borehole. Mohanty (
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