2006 Volume 62 Issue 4 Pages 780-792
Thick deposits of Pleistocene strata are found at deeper depths below the seabed at Kobe Airport which was constructed offshore of Kobe Port. The Pleistocene Clays at the Osaka Bay are quasi-over-consolidated and their consolidation properties have not been well understood. Moreover, the drainage capacity of gravel or sand strata that interlay between the Pleistocene Clays was not clearly understood. In order to examine the settlement behavior of the Clays, a special precise measurement system over a unit depth of 1 or 3 m intervals was installed to measure both the compressions as well as the excess pore water pressures over the entire depths of the Upper Pleistocene Clays. The measurements covered the compressions of Upper Pleistocene Sand and Gravel layers, and those of Ma12 and uppermost Ma11 Clays that are to be brought into a normally consolidated state due to the airport fill load. Based on the measurements, it was found that the pre-consolidation pressure, pc, of Ma12 is function of the strain rate that is highest near the upper drainage boundary and also that the field pc value is smaller than that of the laboratory result because of the low strain rate in the field. The drainage capacity of sand and gravel layers was also found to be good.