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Mine Safety and Health Administration (MSHA) 1100 Wilson Boulevard, 21st Floor Arlington, VA 22209-3939 |
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The initial calculation in determining the volume of material being blasted typically involves determining the "burden." Burden is the distance between the bore hole and the area-of-relief. Often, burden is visually estimated because of the inherent difficulty in measuring the face. In other cases, a "burden pole" is used in conjunction with a measuring tape to determine the "maximum burden" in a certain area of the shot. Rarely however, is a highwall straight and vertical. More likely, the highwall is irregular with some portions that are undercut and other areas where overhangs exists. Therefore, these techniques often miss important characteristics of the face that should be taken to account when determining explosive charges.
To successfully design a blast, the actual volume of material being blasted needs to be determined so that explosive energy can be properly distributed. An important tool available to assist with this determination is a "laser profiler." This tool provides the ability to profile the face to be blasted. Profiling indicates areas of the highwall where excessive burden is present, or areas where too little burden exists. Both 2D and 3D profilers are available.