Published: Jan 1960
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This paper presents results of extended repetitive plate-loading tests which have been performed at the Naval Auxiliary Air Station, Fallon, Nev. and the Naval Air Station, Lemoore, Calif. These tests were performed on low test embankments constructed on prepared subgrade of compacted local fill and surfaced with various thicknesses of untreated or cement-treated subbase. The subgrade and fill materials consisted generally of fine sandy silts and silty sands. Subbase material at Fallon was a sandy gravel, with maximum size of 1 in. At Lemoore the subbase was constructed with the same fine sandy silt and silty sand used as fill modified with the addition of 2½ per cent of portland cement. Total loads of up to 75,000 lb were applied to the subbase or subgrade through 30-in. diameter steel plates. Load repetitions were applied rapidly and were varied up to 500 cycles. Conventional static plate-loading tests were made at the start and at the conclusion of each series of repeated loadings. Results are represented as plots of deflection versus number of cycles of loading and of unit load versus deflection. Deflections were found to increase with number of repetitions of a constant load. Tabulations show variations of Westergaard coefficient k with deflection. It was found that in general the coefficient k increased with load repetitions. Comparisons were made between results obtained by this method and the current Canadian method.
Gordon, Bernard B.
Head, Foundation Engineering Division, Porter, Urquhart, McCreary & O'Brien, San Francisco, Calif.