A STUDY ON DETERIORATION OF DEFORMATION AND STRENGTH CHARACTERISTICS OF SATURATED CLAYS SUBJECTED TO CYCLIC LOADING BASED ON DAMEGE MECHANICS

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In this research, investigated was the deterioration of strength and deformation characteristics of saturated clays subjected to cyclic loading, being based on the concept in damage mechanics. For two-year periods of project, a series of undrained cyclic triaxial tests was carried out for normally consolidated clays and over-consolidated clays. In the first year, the deteriorative characteristics of mechanical properties of saturated clays subjected to cyclic loading were investigated through experimental results of normally consolidated clays, and the characteristics of deterioration were formulated in term of an index of deterioration (damage variable). In the second year, undrained cyclic triaxial tests for over-consolidated clays were performed, and the applicability of the proposed method to the cases of over-consolidated clays was examined.The main conclusions in this research are summerized as follows:(1) The deformation characteristics of saturated clays deteriorate most remark … More ably during and after cyclic loading. Therefore, it is reasonable to choose the coefficient of deformation as an index of deterioration for saturated clays.(2) The deterioration of deformation characteristics of saturated clays is influenced significantly by the strain rate on cyclic loading.(3) The undrained strengths of the clay subjected to cyclic loading and the over-consolidated clay with static stress history are the same if they are in the same effective stress state. Therefore, the deterioration of the undrained strength of the former can be estimated with the procedure to predict the undrained strength of the latter.(4) The deterioration of deformation characteristics of saturated clays is influenced not only by the decrease of mean effective stress but also by the disturbance due to cyclic loading. To evaluate the effect of the disturbance which is dependent of strain history on cyclic loading, an index of deterioration is proposed newly in this study on the basis of the concept in damage mechanics.(5) A method for predicting the stress-strain relations of saturated clays with cyclic loading history is derived through experimental knowledges, and its applicability to the cases of random cyclic loading is confirmed. Less