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An experimental study was carried out to evaluate the influence of silt content on cone penetration measurements and its implication for soil classification. The investigation includes twenty-seven peizocone tests in saturated salty sand samples, which had been prepared in a big rigid thick walled steel cylinder-testing chamber. The samples were prepared with several different silt contents ranging from 0 to 50 percent and were consolidated at three-overburden effective stresses including 100, 200 and 300 kPa. This study showed that, the amount of silt content in sand is an important parameter affecting CPT results. As the silt content increases, the cone tip resistance decreases. The recorded excess pore water pressure during sounding was increased with increasing silt content. It is also concluded that friction ratio, in general, increases with increasing silt content. The method presented by Robertson and Wride [25] and Olsen [17] to evaluate soil classification are also verified.

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An experimental study was carried out to evaluate the liquefaction resistance of silty sand utilizing laboratory techniques. In this study, liquefaction potential of silty sand by using cyclic triaxial tests on frozen samples retrieved from calibration chamber and constructed samples by dry pouring method were investigated. Correlation between cone penetration resistance and cyclic strength of undisturbed silty sand samples are also examined using CPT calibration chamber and cyclic triaxial tests. The cone penetration tests were performed on silty sand samples with fine contents ranging from 0% to 50% and overburden stresses in the range of 100-300 kPa. Then the soil sample in calibration chamber, in the same way that soil samples were prepared during CPT sounding, was frozen and undisturbed soil specimen retrieved from frozen soil sample were tested using cyclic triaxial tests. Analysis of results indicates that the quality of frozen samples is affected by fine content and overburden pressures. Also, using data obtained in this research, the relationship between cone tip resistance and cyclic resistance ratio (CRR) for silty sand soils will be presented. These correlations are in relatively good agreement with field case history data. Also increasing confining pressure in silty sand material increases the cone tip resistance and generally, cyclic resistance ratio increases by increasing silt content.

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This paper highlights the effect of silt content on cone tip resistance in loose silty sand. In this study, twenty-seven cone penetration tests are performed in saturated silty sand samples with several different silt contents ranging from 10 to 50 percent. The samples are consolidated at three overburden stresses including 100, 200 and 300 kPa. It is shown that, as the silt content increases, the cone tip resistance decreases. In high percent of silt (30-50%), the cone tip resistance decreases more gently compared with low percent of silt (0-30%). It is also concluded that the method proposed by Olsen (1997) for stress normalization of cone tip resistance compared with the Robertson and Wride (1998) method has better agreement with the obtained results. To evaluate liquefaction potential of loose silty sand, the method presented by Robertson and Wride (1998) is also studied. The results showed that the use of Robertson and Wride (1998) method to estimate the fine content from CPT data causes some uncertainty especially for high silt content (FC>30%).

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This paper discusses the applicability of a simple model to predict pore water pressure generation in non-plastic silty soil during

cyclic loading. Several Stress-controlled cyclic hollow torsional tests were conducted to directly measure excess pore water pressure

generation at different levels of cyclic stress ratios (CSR) for the specimens prepared with different silt contents (SC=0% to 100%).

The soil specimens were tested under three different confining pressures (&sigmaƉ= 60, 120, 240 kPa) at a constant relative density

(Dr=60%), with different silt contents. Results of these tests were used to investigate the behavior of silty sands under undrained

cyclic hollow torsional loading conditions. In general, beneficial effects of the silt were observed in the form of a decrease in excess

pore water pressure and an increase in the volumetric strain. Modified model for pore water pressure generation model based on

the test results are also presented in this paper. Comparison of the proposed pore pressure build up model with seed’s model

indicates the advantage of proposed model for soil with large amount of silt.