There are 36 (50ms) downhole delay detonators in a parallel-series circuit, with each series consisting of nine (9) detonators. The length of the detonator's copper leg wires is 24 ft each. The round is connected to the permanent firing line through 100 ft of duplex 20 AWG copper wire. There are 600 ft of 10 AWG duplex copper permanent firing lines extending back to the firing switch. Next, are 80 detonators arranged in a parallel-series circuit consisting of 20 (25ms) downhole delay detonators per series. The circuit is connected to the firing line by 300 ft of duplex 20 AWG copper connecting wire that is located 1200 ft from the firing switch. Finally, there is another parallel-series circuit consisting of 18 (75ms) delay detonators in each of the three series. This final circuit is connected 2000 ft away from the firing switch along the permanent firing line ( 10 AWG duplex copper wire) by 300ft of 20 AWG duplex copper wire. 20 ft copper leg wire detonators are used in the last two blasting circuits. The power source is a 440-volt AC power line. One detonator is placed in each of the blast holes.

Determine the following:
1. The total resistance of the combined blast circuits.
2. The total current supplied to the detonators in the blasting circuit
3. The total current supplied to each of the three blasting circuits.
4. The total duration of the blast.
5. The quantity of explosive used for the entire blast, if each of the boreholes were
loaded to a height of 5m, with the charge weight being 8.5 kg/m.

Answer rating: 100% (QA)

1 The total resistance of the combined blast circuits is 96 ohms This is because there are 36 50ms downhole delay detonators in a parallelseries circuit with each series consisting of nine 9 detonator... View the full answer