细粒含量对饱和砂类土液化强度的影响

Effect of fines content on liquefaction resistance of saturated sandy soils

为研究细粒含量FC对不同密实状态饱和砂类土液化强度CRR的影响,将不同FC的砂类土试样分为3组:(1)相同的相对密实度Dr=50%;(2)相同的孔隙比e=0.90;(3)相同的骨架孔隙比e_(sk)=1.20,对不同FC和密实状态(Dr、e和e_(sk))的砂类土进行了一系列不排水循环三轴试验。试验结果显示:e或Dr相同的砂类土CRR随着FC的增加逐渐降低;具有相同e_(sk)砂类土的CRR随FC的增加迅速增大,砂类土的CRR与D_r、e或e_(sk)都没有较好的相关性。分析表明:不同FC和密实状态砂类土的CRR随等效骨架孔隙比e_(sk)~*的增大而降低,两者呈现较好的负幂函数关系,这表明考虑细粒影响程度的e_(sk)~*是合理表征不同种类砂类土CRR的一个物理状态指标。通过对比已有的砂类土的试验结果发现:砂类土中的砂粒是影响CRR的重要因素,且随着砂粒的形状从圆状向角状变化,砂类土的总体CRR逐渐增大。

In order to investigate the effect of fine content（FC） on liquefaction resistance（CRR） of saturated sandy soils with different densities, three cases are categorized： 1） at a constant relative density Dr = 50%; 2） at a constant void ratio e = 0.90; 3） at a constant skeleton void ratio esk = 1.20. A series of undrained cyclic triaxial tests were performed on sandy soils with different FC and density state（Dr, e and esk）. The test results show that an increase in FC causes a decrease in CRR of sandy soils at a constant Dr or e. and the CRR of sandy soils at a constant esk^＊ will increase with the increase of FC. There is no clear correlation between Dr, e or esk and CRR for saturated sandy soils with different FC. Moreover, the test data in this study reveal that the CRR of sandy soils with different FC and density decease with the increase of the esk^＊. A power relationship between a decrease in CRR and an increase in esk^＊ indicates that the fraction of the fines contributes to the formation sustaining the loads can be used as an index to uniquely evaluate the CRR of different kinds of sandy soils. By comparing the published results of the other sandy soils, it is found that the sand grain is an important factor affecting the CRR of sandy soils, and the overall CRR of the sandy soils will increasing as grain shape changing from spherical to angular.