不同粒径比下含细颗粒砂土液化特性的试验研究

Experimental study on liquefaction characteristics of sand with fines under different particle size ratios

利用带有弯曲元的GDS动三轴仪,对3种不同粒径比下含细粒砂土进行不排水循环三轴和弯曲元试验,分析了细颗粒含量、密实度、初始有效围压、制样方法以及粗细颗粒粒径比对砂土液化特性的影响,探讨了等效骨架孔隙比e能否合理统一表征不同初始状态以及不同粒径比下含细粒砂土的抗液化强度。研究结果表明:等效骨架孔隙比e可以合理解释低塑性粉粒含量对各种砂性土抗液化强度CRR15和小应变剪切模量G0的影响,两者均呈负幂数关系,且G0通过e与CRR15呈现一一对应关系,为含细颗粒砂土液化判别提供了一种新的经验性方法。其次,通过e表征砂性土抗液化强度时应当考虑初始围压和制样方法的影响,特别对于孔隙比较小和细颗粒含量较低时。粒径比χ在小于9.9时对CRR15与e的关系影响较大,而当χ大于9.9时,关系曲线几乎重合一致,且发现等效相对密实度Dr与3种砂性土的抗液化强度呈单调递增线性关系,不受细颗粒含量和粒径比的影响。

A series of undrained cyclic triaxial and bender element tests are carried out on sandy soils with three different particle size ratios by using the GDS cyclic triaxial apparatus with bender elements.The effects of fines content,density,initial effective confining pressure,sample preparation method and particle size ratio on liquefaction characteristics of sandy soils are analyzed.Whether the equivalent skeleton void ratio e can reasonably and uniformly characterize the liquefaction resistance of the sandy soils under different initial states and different particle size ratios is discussed.The results show that e can reasonably quantify the influences of low plastic fines content on liquefaction resistance CRR15 of various sandy soils,showing a negative idempotent relationship between CRR15 and e.There is also a unique relationship between small strain shear modulus G0 and e,which indicates a unique relationship between CRR15 and G0.It provides a new empirical method for the evaluation of liquefaction resistance of the sandy soils.Meanwhile,the influences of the initial confining pressure and sample preparation method should be considered when e is used to characterize the liquefaction resistance,especially for smaller void ratio and fines content.When it is less than 9.9,the particle size ratioχhas a great influence on the relationship between CRR15 and e,while it has a negligible effect when it is greater than 9.9.It is found that there is a unique relationship between equivalent relative density Dr and CRR15 for the tested three sandy soils,despite of the fines content and particle size ratio.