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WALL CONTROL BLASTING TECHNIQUES TO MINIMIZE DAMAGE TO THE ROCK AT THE LIMITS OF SURFACE AND UNDERGROUND EXCAVATION, IN ORDER TO ENHANCE SAFETY STANDARD AND ECONOMY *** Author: Partha Das Sharma, B.Tech(Hons.) in Mining Engineering, E.mail:, Blog/Website: ABSTRACT Wall failures are costly and often life threatening. The goal of efficient wall control blasting is to make transition from a well fragmented rock mass to an undamaged slope in as short a distance as possible. This can be quite challenging due to the many factors that influence wall damage. To develop efficient designs one must have a basic understanding of wall failure mechanisms as well as limitations of wall control procedures. In addition, it is imperative, design be precisely implemented, evaluated and refined on a continuous basis. The release of energy during blasting produces reactive forces, which cause the deterioration of the remaining rock face. Pre-splitting and trim blasting are the key techniques adopted to protect final rock faces. However, even these well known techniques are applied; slope failures and back damage may persist. The key parameters within the control of the blasting engineers are type and energy in the hole, drilling pattern, hole depth, hole diameter, hole angle, bench geometry and blast timing. An understanding of mechanisms of all the aspects is needed for good designing for blast for wall control and slope stability. 1. INTRODUCTION: Wall control blasting is the technique used to obtain a pit wall, free of backbreak and loose rock that will stand safely at the required wall angle for extended periods of time. Direct damage to the excavation limit due to blasting is usually found in the form of backbreak or overbreak, crest fracture and loose rock on the face. The mine operator has a number of tools available for minimizing or eliminating these problems. Techniques include changing the explosive type, or changing the blasthole diameter, by decoupling the explosive, by decking, and by changing the burden and spacing. Changing the depth of subgrade drilling or the stemming height can reduce crest fracture and any resultant narrowing of the width of safety benches. Changing the millisecond delay timing and the rotation of the round may also be helpful in eliminating these problems. The rock characteristics and geology must be considered when designing controlled blasts as these have an important influence on the final results. The compressive strength, crushing strength and tensile strength of the rock should be known. The frequency and orientation of joints and fractures in the rock are also important parameters. These variables cannot be controlled but must be determined by suitable field and laboratory techniques. Author: Partha Das Sharma, (B.Tech-Hons., Mining Engg.), E.mail:, Website: Page 1


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