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Factors Within The Blaster-In-Charge’s Control that <br />influence Ground Vibrations <br />Factor <br />Influence On Ground Vibration <br />Significant Moderate Insignificant <br />Charge-weight/delay X <br />Delay Interval X <br />Burden and Spacing X <br />Stemming amount X <br />Stemming type X <br />Charge length and diameter X <br />Borehole accuracy X <br />Direction of initiation X <br />Charge-weight per blast X <br />Charge depth X <br />Exposed detonating cord X <br />Charge confinement X <br />Table 3. Factors within the blaster-in-charge’s control that influence ground vibrations. <br /> <br />Factors Outside The Blaster-In-Charge’s Control That Influence <br />Vibrations <br />Factor Significant Moderate Insignificant <br />Surface terrain (topography) X <br />Type of rock X <br />Depth to grade or ore (overburden) X <br />Weather conditions X <br />Table 4. Factors outside the blaster-in-charge’s control that influence vibrations. <br /> <br />Procedures to reduce Ground Vibrations Regarding Blast Design Factors <br />Design Factor Procedure <br />Reduce charge- <br />weight/delay <br />Reduce the charge-weight/delay in a manner consistent with acceptable fragmentation and square <br />root scaling. Consider using smaller boreholes or explosive deck in a new blast design. <br /> <br />Explosives selection <br />Select explosives based on their physical properties, performance characteristics and sensitivities. Be <br />aware of any limitations and precautions recommended by product manufacturers for sensitivities <br />that may cause sympathetic detonations between boreholes or between chargers within a single <br />borehole. <br />Initiation system <br />selection <br />Select initiation systems for more accurate and precise firing times. Electronic initiation systems <br />are used in critical vibration environmental locations. <br /> <br />Delay timing strategies <br />and intervals <br />Change or modify the direction of initiation, especially for pre-split lines. <br />Maximize internal relief by using one to two free faces to blast, by either increasing or decreasing <br />delay times while maintaining desired muckpile shape and degree of fragmentation. <br />Use signature waveform analysis to determine timing intervals for destructive interference. <br /> <br />Blast Designs <br />Adjust blast designs to accommodate smaller charges while maintaining the same powder (energy) <br />factor. This includes, hole diameter and depth, spacing, burden, explosive type, and possible use of <br />separate decks in each hole. <br />Table 5. Procedures to Procedures to reduce Ground Vibrations Regarding Blast Design Factors. <br /> <br />