Evaluation of fine contents of silty sands using CPTU results

Abstract

The cone penetration test with measurement of pore pressure (CPTU) has been widely used in evaluation of liquefaction potential. Estimating the liquefaction resistance of non-clean sands using cone penetration resistance- based techniques can be accomplished by three methods: I) calculated equivalent clean sand (Ishihara, 1985; Seed & Dealba, 1986; Robertson & Wride, 1997). II) The chart-based solution in terms of a measured soil index (Olsen & Koester, 1995; Olsen, 1997). III) Direct correlation to field case histories (Shibata & Teparaksa, 1988; Stark & Olsen, 1995; Baziar & Ziaie-Moayed, 1998). It is important to note that the above approaches are sensitive to the amount of silt content. The main object of this paper is to report on the new approach to evaluate the fines content based on CPTU results such as t50. In this study, eleven cone penetration tests are performed in saturated silty sand samples with several different silt contents ranging from 1 to 50 percent in the calibration chamber. The standard piezocone is inserted into the chamber by a hydraulic system. Standard piezocone used in this investigation has 10 cm 2 projected tip area and a 150-cm 2 friction sleeve area. In this penetrometer friction sleeve is sited immediately behind the cone tip. The samples are consolidated at three overburden stresses including 100, 200 and 300 kPa. The pore pressure dissipation tests are also carried out in samples with different silt content and t50 parameters. From the obtained results, it can be concluded that, as the t50 increases the fine content increases. At the end, the correlation between t 50 and fine content is presented. The complete results will be presented in the main paper.