K_0-CONSOLIDATION IN A TRIAXIAL CELL AND EVALUATION OF IN-SITU K_0 FOR MARINE CLAYS WITH VARIOUS CHARACTERISTICS

摘要

A series of K_0-consolidation tests in a triaxial cell was carried out for marine clays collected from different areas in the world in order to investigate the behavior during K_0-consolidation tests and evaluate K_0-values that are required for laboratory tests with recompression techniques, FEM analysis using elasto-plastic constitutive equations, etc. It was confirmed that the famous equation K_(0NC)= 1 - sin φ′is useful; however, the definition of φ′ should be concerned. In the case using φ′ corresponding to a critical state line, i.e. (qlp)_(max), the equation underestimates K_(0NC) by 0.05; in contrast, in the case using φ′ corresponding to a peak strength, i.e. (q)_(max), the equation overestimates K_(0NC) by 0.05. This study proposes a procedure for estimating the in-situ K_0-value. For a representative undisturbed clay sample, K_0-consolidation and K_0-overconsosidation tests (i.e. SHANSEP test) are consecutively carried out to obtain the K-OCR relationship. Using the profile of OCR obtained from a series of oedometer tests, the K-value corresponding to the OCR can be calculated as the in-situ K_0. The K_0-values obtained from both the K_0-overconsolidation test corresponding to the OCR in the laboratory and the flat dilatometer test (DMT test) in the field compared well.