Effect of anisotropy on drained and undrained shear behavior of in-situ sandy soils

Abstract

Two different types of undisturbed cylindrical specimen (V-specimen : the axis is parallel to the direction of sedimentation, and Hspecimen : the axis is perpendicular to the direction of sedimentation), were prepared from high quality undisturbed sand column obtained by in-situ freezing technique. A series of drained compression and extension tests (CD, test, CD, test) and cyclic undrained triaxial tests (liquefaction test) on these samples were performed in order to investigate the effect of the anisotropy on the drained and undrained shear behavior. Following were concluded. 1) The effect of anisotropy on both internal friction angle and liquefaction strength is negligible. 2) The difference in deformation characteristics between V and H-specimens for Holocene soil layer appeared in both CD and liquefaction tests implies that in-situ soil is easier to compress in horizontal direction than in vertical direction. 3) The effect of anisotropy on deformation characteristic of Pleistocene sand samples is not so remarkable as that of Holocene sand. INTRODUCTION cal specimen, V and H-specimen, were used in this study. As widely known, the inherent anisotropy of in-situ soils has some effects on their mechanical properties. Based on a series of liquefaction tests on undisturbed (obtained by block sampling) and reconstituted samples, Miura and Toki pointed out that the anisotropy of both samples has significant effects on their liquefaction strength. However, the data on the anisotropy of in-situ sandy soils is quite limited and no systematic research on high-quality undisturbed sand samples has been done. The objective of the present paper is to investigate the effect of the anisotropy of undisturbed sand samples recovered by in-situ freezing technique on their drained and undrained cyclic shear behavior by performing a series of CD and liquefaction tests. Two different types of undisturbed cylindriSAMPLE PREPARATION AND PHYSICAL PROPERTIES TESTED Two different types of cylindrical shape test samples, 5 cm in diameter and 10 cm in height, were prepared from a frozen sand column obtained by the in-situ freezing technique. Hatanaka et al. described the detail of the in-situ freezing method. The sample whose axis is parallel to the direction of sedimentation is designated as V-specimen, while the sample whose axis is perpendicular to the direction of sedimentation is called H-specimen as illustrated in Fig.1. The physical properties of samples used in CD and liquefaction tests are indicated in Table 1 and 2, respectively.