Direct Simple Shear Testing for Post-Cyclic Degradation in Stiffness of Nonplastic Silt
Song, BW
Dasan Consultants Company, South Korea

Yasuhara, K
Ibaraki University, Japan

Murakami, S
Ibaraki University, Japan

(Received 22 February 2002; accepted 5 April 2004)

Abstract
Using a sequential procedure of cyclic and postcyclic direct simple shear tests, the stiffness degradation characteristics of nonplastic silt are studied during and immediately after cyclic loading by direct simple shear (DSS) tests. The results from cyclic and postcyclic DSS tests were interpreted using methods modified from those adopted for cyclic and postcyclic triaxial tests. In particular, the effect of initial static shear stress (ISSS) on postcyclic behavior is considered for nonplastic silt. The findings obtained from the sequential DSS testing on nonplastic silt are: (i) during cyclic loading the tendency of the stiffness to decrease with increasing normalized pore pressure is different for plastic and nonplastic silts, (ii) since the relation between equivalent stiffness ratio and single amplitude shear strain for nonplastic silt does not fit the Hardin-Drnevich Model, new modified relation is needed, (iii) the larger the ISSS is, the faster the decrease in stiffness ratio becomes, and (iv) the decrease of stiffness ratio for nonplastic silt is less marked than that for plastic silt when plotted against the normalized pore pressure after cyclic load.

Keywords:
constant volume condition, cyclic loading, cyclic test, degradation of stiffness, direct simple shear test, monotonic test, postcyclic loading, silt

Paper ID: GTJ11194
DOI: 10.1520/GTJ11194

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Author Song, BW Affiliation Dasan Consultants Company, South Korea Author Yasuhara, K Affiliation Ibaraki University, Japan Author Murakami, S Affiliation Ibaraki University, Japan Author Song BW, Yasuhara K, Murakami S Title Direct Simple Shear Testing for Post-Cyclic Degradation in Stiffness of Nonplastic Silt Symposium , Committee on