CYCLIC STRENGTH AND DEFORMATION OF NORMALLY CONSOLIDATED CLAY

ABSTRACT Several series of stress-controlled repeated triaxial compression tests are carried out on a remolded soft clay. Cyclic strength and deformation behavior are analyzed in terms of both effective and total stresses and discussions are made particularly on the influence of stress- induced anisotropy. From the effective stress point of view, the followings are emphasized as main conclusions. 1) The cyclic undrained strength is almost independent of the frequency and the duration of repeated loading 2) The cyclic strength tends to decrease due to remolding effect a little degree. 3) The dynamic pore-water pressure normalized by the confining pressure can be expressed by a unique hyperbolic function in relation to the shear strain. On the other hand, a consideration in terms of the total stress on cyclic strength and deformation is characterized by: 1) Within the range of the low confining pressure, the cyclic strength surpasses the static one by 5 through 20%. 2) The cyclic strength and the deformatoin modulus are not so strongly influenced by loading frequency. On anisotropically and isotropically consolidated clays, the difference in dilatancy and deformation is caused by the pre-shear effect. This fact is recognized from the viewpoint of the effective stress and the total one. On the contrary, the cyclic strength depends on the strain amplitude. However, as long as the cyclic strength is defined at the 15% strain amplitude, no difference between strengths of anisotropically and isotropically consolidated clays can be expressed in terms of both effective and total stresses.