Influence of Non-Plastic Fines on Laboratory Shear Wave Velocity Measurements and Cyclic Resistance Lalita G. Oka, Ph.D., A.M.ASCE 1 ; and Mandar M. Dewoolkar, Ph.D., P.E., M.ASCE 2 1 Dept. of Civil and Geomatics Engineering, California State Univ., Fresno, 2320 E. San Ramon Ave, M/S EE94, Fresno, CA 93740. E-mail: loka@csufresno.edu 2 School of Engineering, Univ. of Vermont, 213 Votey Hall, 33 Colchester Ave., Burlington, VT 05405. E-mail: mdewoolk@uvm.edu Abstract Most foundation design projects in seismically active regions include liquefaction potential evaluations at least to screen sites that are potentially susceptible to liquefaction. The existing guidelines based on the simplified procedure or the cyclic stress method for such screening procedure is based on field correlation that uses either field penetration resistance from standard penetration test and cone penetration test or shear wave velocity (V s ) measurements. Fines correction factor is one of the corrections that is routinely applied to these field measurements to estimate cyclic resistance ratio (CRR) of the foundation soil. However, soils containing fines, especially non-plastic fines, have been reported liquefied. A laboratory investigation was carried out to examine the effects of non-plastic fines on shear wave velocity measurements and undrained cyclic strength of a sand with varying percentages of non-plastic fines. Top and bottom platens of a triaxial cell were equipped with bender elements to facilitate shear wave velocity measurements on the same specimen that was tested cyclically. In general, V s and CRR decreased as fines content increased in comparison to the host sand. The results do not quite support the present form of fines correction in the V s -based simplified procedure. Keywords: Liquefaction; Cyclic resistance; Shear wave velocity; Fines content; Fines correction; Cyclic stress method; Simplified procedure INTRODUCTION Potential liquefaction of foundation soils can be dangerous to the structures supported by the foundations and can cause loss of life and property. Liquefaction potential evaluation of potentially liquefiable soils throughout the world in seismically prone regions is often performed using the ‘simplified procedure’, originally proposed by Seed and Idriss (1971) and Whitman (1971) and later updated by Youd et al. (2001). These guidelines consist of empirical correlations between the field measurements such as SPT blow count (N), or cone tip resistance (q c ), or shear IFCEE 2018 GSP 295 309 © ASCE IFCEE 2018 Downloaded from ascelibrary.org by Colorado State Univ Lbrs on 12/13/18. Copyright ASCE. For personal use only; all rights reserved.