Experimental Study On Static Liquefaction Of Saturated Silty Sand

It was known that clean sandy isn’t in extension all the while, and a significant amount of fines exist in alluvial and hydraulic deposit silty sand. Therefore, the static liquefaction of silty sand has been studied by many scholars, but there are different view on the liquefaction resistance of silty sand increase or decrease. So in this context the paper studied the characteristics of static liquefaction in silty sand through studying fines size and fines plastic which was done with CU tests. The main research of this dissertation is as follows:1. The undrained triaxial tests were performed on Fujian standard sand mixed with three different particle size fines of micro silicon fines、 tail mineral fines、 rock fines. Results show that under lower confining pressure and fines content, the liquefaction resistance of silty sand increases significantly with the increase of mean grain diameter ratio(D50-sand/d50-fines), from full liquefaction to fully stable state. And the strength of the silt sand is not increasing with the increase of fine content at same condition. However, both static liquefaction phenomenon occurred for three kinds of silt sand when the fine content increases to 30%. This moment, there is little influence of static liquefaction Properties with the increase of D50-sand/d50-fines, and the liquefaction resistance of silty sand increases weak with the increase of fine content.2. In order to investigate the effect of plastic fines on structure and strength of silty sands, the undrained triaxial shear experimental study on remolding silt with low plastic Kaolinite fines and plastic bentonite fines was performed. The test results show that: the shear properties of two silt samples is completely different, silty sands mixed with low plastic fines exhibited completely static liquefaction characteristic under the fines content of 5%、10%、15%、20%, and it does not has connection with consolidation confining pressure. But sample mixed with plastic fines exhibited static liquefaction with a range of residual shear strength、temporarily liquefaction and sufficient stability phenomenon but not completely static liquefaction in certain fines content, it has high stability and the liquefied properties also change with the different of confining pressure.3. The role of fines in soil structure was interpreted by the equivalent intergranular void ratio. The study show that this parameters can be better analyzed the mechanical properties of soil structure which mixed with not plastic fines. D50-sand/d50-fines and fines content have significant effect on silty sand strength when sand particles dominate control function in the soil, conversely, D50-sand/d50-fines and fines content have little effect on silty sand strength when fines in a controlling position in the soil. But the liquefied properties of silty sand is not able to analyze by equivalent intergranular void ratio which mixed with plastic fines, it need to take the parameters of plasticity index IP and stress ratio h into account.