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A "sonic pile-hammer" is now driving the piles for its first building foundation--that of the new building for the Geology Department between the University Museum and Malinckrodt. Since the hammer causes only a fraction of the ground and air vibrations caused by conventional steam hammers, it insures the security of the famous glass flowers housed in the Museum (and also of the curators who reputedly are even more sensitive than the glass flowers).
About five days ago one pile was driven with a steam hammer and seven piles with the sonic hammer. Then the steam-driven pile and one of the sonic-driven ones were load-tested. Specifications called for a minimum load of seventy tons, but as a safety factor both were tested for double the design load. It was found that with the 140 ton load the steam-driven pile sunk twice as far into the ground as the sonic-driven pile did.
Conceived by Albert G. Bodine, a physicist in California, the hammer imparts to the pile longitudinal vibrations with the resonant frequency of the pile. Resonant frequency insures minimum loss of energy, in contrast to the conventional steam hammer process in which most of the driving energy is lost. The pile is driven into the ground as the vibrations cause it to expand and contract at a very high rate of speed. The sonic process takes one minute, as compared to 12-15 minutes for the conventional method.
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