SMALL STRAIN CHARACTERISTICS OF SOILS IN HUALIEN, TAIWAN

YUKIHISA TANAKA, KOJI KUDO, KOICHI NISHI, TOSHIRO OKAMOTO, TETSUYUKI KATAOKA and TERUYUKI UESHIMA

ABSTRACT: The Hualien Large-Scale Seismic Test (HLSST) program is currently to investigating soil-structure interaction during large earthquakes in Hualien, a region in Taiwan of high seismicity. This paper summarizes the laboratory tests, including cyclic triaxial tests, conducted to obtain small strain characteristics of the soils for dynamic response analysis and to characterize the ground of the test site. Factors affecting accurate evaluation of small strain characteristics of soils are also investigated in this paper. The following conclusions are drawn. (1) According to the results of cyclic triaxial tests, shear modulus at small strain by local measurement is discernibly larger than that by external measurement because of the effect of bedding errors. However, there seems to be almost no effect of bedding error in hysteresis damping at small strain level. (2) For sands, the shear wave velocities measured by cyclic triaxial tests are almost the same as those by in-situ velocity logging, whereas shear wave velocities of gravelly soils measured by cyclic triaxial tests are much smaller than those by in-situ velocity logging. This difference might be attributable to the effect of heterogeneity in the gravelly layer .

Key words: cyclic triaxial test, deformation property, frozen sample, gravelly soil, site investigation, velocity logging (IGC: D7)