MODELING ANISOTROPIC BEHAVIOR OF GRAVELLY LAYER IN HUALIEN, TAIWAN

YUKIHISA TANAKA

ABSTRACT : The Hualien Large-Scale Seismic Test (HLSST) program is under way to investigate soil-structure interaction during earthquakes in Hualien, a high-seismicity region in Taiwan. Since anisotropic characteristics of the gravelly layer affect the results of earthquake observation and forced vibration tests, the gravelly layer was modeled by an orthotropic elastic body in this paper to enhance the accuracy of the dynamic simulation analysis . The following conclusions are drawn. (1) The gravelly layer was modeled by an orthotropic elastic body whose model parameters were partly deter- mined using results of earthquake observation. (2) The azimuth dependency of the shear wave velocity measured by the cross hole velocity logging can be expressed by the orthotropic elastic body model. (3) It can be explained by the orthotropic elastic body model that values of shear wave velocity measured by down-hole velocity logging were divided into two groups. (4) The initial shear moduli of undisturbed samples from the gravelly layer evaluated by cyclic triaxial tests agree with the calculated results by the orthotropic elastic body. (5) The anisotropic behavior of the model building during forced vibration tests can be expressed successfully by the orthotropic elastic body.

Key words: anisotropy, (cyclic triaxial test), (forced vibration test), (gravelly soil), (initial shear modulus), (velocity logging) (IGC: D7)