Author(s): Malcolm Mellor
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Keywords: No Keywords
Abstract: Icebreaking tests utilizing high pressure air and CO2 (70-90 MPa), low pressure air (17 MPa) and fuel/oxidant combustion (2.3-4.3 MPa) are reviewed and the results are interpreted. Applying cube root energy scaling to test discharges of approximately 1 MJ, it appears that fracture craters up to about 5.8 m/MJ 1/3 in diameter can be formed by optimum underwater blasts. Optimum ice thickness seems to be about 0.4 m/MJ1/3, i. e. optimum discharge energy for ice t (m) thick is about (t/0.4) 3 MJ. Optimum discharge depth for optimum energy is probably in the range 0-0.6 m/MJ1/3. The specific energy for an optimum blast is < 0.1 MJ/m 1/3, which is about the same as for a high explosive blast when specific energy is based on gas expansion rather than heat of explosion. Critical ice thickness for shallow discharges is probably about 0.6 m/Mj1/3, and critical charge depth for discharges optimized to shallow depth is about 1.8 m/Mj1/3 Practical systems for clearing or displacing ice could be based on air guns developed for offshore seismic work, with gun pressure in the range 17-20 MPa and single-gun energy up to about 11 MJ. A procedure for making preliminary design calculations and safety appraisals is outlined, and it is concluded that a working "Super-Bubbler" need not be very complex or expensive.
Year: 1984