SETTLEMENTS IN FINE-GRAINED SOILS UNDER CYCLIC LOADING

Kazuya Yasuhara, Satoshi Murakami and Noritaka Toyota

ABSTRACT : Based on the methods previously presented by the authors (Yasuhara et al., 1992, 1994, 1996) for predicting the degradation in strength and stiffness of soft clays in the course of cyclic loading, a methodology has been developed to estimate the cyclic loading-induced settlements. The method also includes not only immediate settlements but also post-cyclic long-term settlements due to dissipation of cyclically induced excess pore pressures in soft soils. The simplified formulae included in the proposed methodology are given as functions of the amplitude of cyclic-induced excess pore pressure normalized by the confining pressure, u/p'c, plasticity index Ip and factor of safety against bearing capacity failure, Fs. The calculations of cyclic-induced settlements were conducted for soft soil deposits with different index and geotechnical properties. The results calculated using the proposed methodology are presented in the form of a design chart to give the settlement versus normalized excess pore pressure ratio relations including the effects of the plasticity�@index and safety�@factor�@for�@bearing�@capacity. An example of the calculated results using the proposed procedure for the earthquake-induced settlements of embankments founded on soft clay, is presented to demonstrate the practicality of the method for design at fields.

Keywords : Cyclic loading, Settlement, Fine grained soil, Excess pore pressure, Plasticity index, Safety factor (IGC : D7/E8)