2024-01-31_REVISION - M1977344 (35)

Home Browse Search

Table 6. Procedure to reduce ground vibrations regarding blast implementation factors Factors Within The Blaster-In-Charge’s Control that influence Air Overpressure Factor Influence On Air Overpressure Significant Moderate Insignificant Charge-weight/delay X Delay Interval X Burden and Spacing X Stemming amount X Stemming type X Charge length and diameter X Borehole accuracy X Direction of initiation X Charge-weight per blast X Charge depth X Exposed detonating cord X Charge confinement X Table 7. Factors within the blaster-in-charge’s control that influence air overpressure Factors Beyond The Blaster-In-Charge’s Control That Influence Air Overpressure Factor Significant Moderate Insignificant Surface terrain (topography) X Type of rock X Depth to grade or ore (overburden) X Weather conditions X Table 7. Factors beyond the blaster-in-charge’s control that influence air overpressure. Procedures Regarding Blast Design Factors To Reduce Air Overpressure Design Factor Procedure Charge-weight/delay Determine charge weight per delay consistent with the distance to nearby protected structures according to cube root scaling and the type of blasting. Consider using smaller boreholes or explosive decks in a new blast design. Delay Interval and direction of initiation Delay time between adjacent boreholes should exceed 1 millisecond for each 0.304 meter (1 foot) to avoid reinforcement of overpressure energy in the direction of initiation. Burden and spacing Adjust blast pattern layout commensurate to borehole diameter to achieve the powder factor appropriate to the rock type. This includes burden and spacing, hole depth, explosive type, and the uses separate decks in each hole. Large charges close to and open face may cause rapid face displacements and generate and elevated air pressure rate. Table 8. Procedures regarding blast design factors to reduce air overpressure. Procedure To Reduce Ground Vibrations Regarding Blast Implementation Factors Field Factor Procedure Drilling Accuracy Ensure good control over drilling so that the planned burden and spacing are those actually achieved by the driller. Good drilling control with also help to reduce the subgrade drilling, and may make it possible to reduce the total charge/borehole. Loading Accuracy Review the drill logs. Properly load boreholes according to the information provided on the drill log. Borehole irregularities that may cause overloading include fracture zones, rubble zones, voids and caverns. Confinement Eliminate buffer blasting and make sure that the toe is cleared of broken rock. Quality Control Review the quality control procedures to ensure that the blast plan is properly implemented.