| Summary: | 碩士 === 國立臺灣科技大學 === 營建工程系 === 99 === Behaviors of high initial Young’s modulus and stiffness degradation were observed on Taipei silty clay, and were applied to the numerical analysis in excavations with advanced soil models. The analysis with consideration of high initial Young’s modulus and stiffness degradation under axial compression condition yields in better prediction results. However, stress paths in a real excavation are different for soil elements at different positions. Thus, the degradation behavior of stiffness for soils under different stress paths should be investigated. This study presented a series of CK0U (K0 consolidation and undrained shearing) unloading-reloading triaxial tests under three stress paths, i.e. AC (axial compression), AE (axial extension), and LC (lateral extension), with bender element tests. Test results demonstrated that both secant Young’s moduli and shear moduli degraded with the increase of strain and stress level. From results of AC and LE tests, stiffness degradation ratios for tested soil versus axial strains are unique (or stress path independent). Nevertheless, the degradation ratio versus the stress level is affected by the failure strain and dependent on stress paths.
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