Effects Of Particle Gradation On Static Liquefaction Behaviour Of Sands

Loose silty sand is a typical sand vulnerable to static liquefaction landslide, so it is necessary to study static liquefaction behavior for loose silty sand. Particle gradation is one of the important factors affecting static liquefaction in loose silty sand. However, the relevant studies are very limited, and merely qualtitative, so it is necessary to carry on further stduy on this subject.In this paper, four series of isotropic consolidation tests were performed to investigate the effects of particle gradation on static liquefaction behavior of sands.In the first series, the uniform coefficient Cu of the sands were changed while the curvature coefficient Cc and the effective paticle diameter d10 were kept constant, so as to study the effects of Cu on their liquefaction potential index (LPI). The purpose of the second series was still to study the effects of Cu on liquefaction potential index (LPI) of the sands, to ensure that the effects of Cu on LPI was not only limited to the sands in the first series .The difference was that the Cc and the d10 of the sands in this series were smaller than those in the first series. In the third series, the Cc of the sands were changed while the Cu and d10 were kept constant, to study the effects of Cc on their LPI. In the fourth series, different fine contents were added to a well-graded sand. Comparing the test results of this series to the former research, we can get the effects of fine contents on LPI of sands with different gradation.The research results show that:(1)LPI of the sands decreases as the Cu increases in a certain range; When Cu is small, the change of Cu has obvious effect on the position of the critical state line, but as the Cu increases to a certain value, the effect becomes weakened.(2)LPI of the sands decreases as the Cc increases. When Cc is small, the change of Cc has obvious effect on the slope of the critical state line,but as the Cc increases to a certain value, the effect becomes weakened;Cc has no effect on the intercept of the critical state line.(3)At low confining presse( p0 '=100kPa), LPI of the sands first increases then decreases as the fine contents increases for sands with different gradation, but the critical fine contents making a sand have the highest LPI is different. At high confining pressure ( p0 '=500kPa), the behavior of two sands influenced by fine contents are not the same as the condition at low confining pressure. The LPI of the sands still first increases then decrases as fine contents increases for a well-graded sand, but it first decreases then increases for a poor-graded sand.Finally, numerical simulation was conducted for the slope with different gradation basing on these test results. Results show that static liquefaction landslide did not happen in a well-graded sand slope, but static liquefaction landslide could happen in a poor-graded sand slope. The effects can be well explained by laboratory tests.The conclusion mentioned above can provide a certain basis for predicting and preventing landslide and other geological disasters, and also can provide a certain basis and data reference for corresponding slope stability analysis.