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• respectively. These strains were produced at the low square root <br />scaled distance of 3.4. No damage to the line was experienced. <br />In view of the above evidence and to provide an additional safety <br />factor to ensure against a gas line rupture, Rimrock stipulates <br />that the peak particle velocity at any point along the gas line <br />will not exceed 6.5 inches per second. <br />Dupont's "Blasters Handbook" utilizes a simple power law formula <br />in relating the weight of explosive charge to the ground <br />vibration predicted at some known distance from the blast. The <br />equation was developed by the U.S. Bureau of Mines through <br />numerous field tests in ground motion transmission over varying <br />geologic conditions. The formula is as follows: <br />V= 160 rRl"1.6 <br />W1 <br />where: <br />• V = peak particle velocity in inches per second <br />R = distance between blast and recording site in feet <br />W = maximum pounds per delay period of 8 milliseconds <br />or more. <br />Using a maximum allowable peak particle velocity of 6.5 inches <br />per second, and a distance of 50 feet, solving the above equation <br />for W yields 45.6 pounds of explosives. No more than this amount <br />should be detonated in each S ms delay to protect the gas line. <br />The blasting plan for the mine utilizes 10 feet deep holes to <br />blast the overburden on a 10 ft. x 10 ft. spacing. It is likely <br />that each hole will be detonated in a separate a ms period, so <br />that less than 11 pounds will likely be detonated in any delay <br />period. <br />4 <br />r~ <br />L <br />