せん断応力除荷時の粘性土の弾性的挙動

Abstract

It is one of the major problems in soil mechanics to describe the mechanical response ofsoils under cyclic loading conditions. The objective of this study is to clarify the stress-strainbehaviors when the loading direction is reversed. For the purpose conventional triaxialtests for a saturated clay were performed in which deviator stress was applied in compressionstate and unloaded to failure in extension state.Stress-strain behavior has been found to be elastic in some portion after the moment ofunloading of shear stress and beyond the portion the behavior begins to be elasto-plastic.Such a limit of elasticity can be determined in stress space and the variation with the defor-mation history having been given before unloading are discussed. On the other hand shearmodulus G can be determined as the slope of the linear portion of stress-strain relationship.The effects of deformation history on G are also discussed.A few of conclusions are summarized as follows:1) A parameter defined as a function of stress ratio at the start of unloading and stressratio at the limit of elasticity appears to be related to shear strain given before unload-ing uniquely in spite of both drainage condition and OCR.2) G is not influenced by the degree of the deformation history if effective mean stressis not altered during deformation history as in drained tests but it decreases in thecase when effective mean stress decreases with shear as in undrained tests for normallyconsolidated clays.