无黏性混合土临界细粒含量的多途径判别研究

临界细粒含量反映了无黏性混合土颗粒级配和结构性对力学性状的重要影响,其值的确定是一个相互验证的过程。假设无黏性混合土具有砂-粉二元结构,在此基础上通过理论分析颗粒骨架于孔隙比的影响,运用土体基本物理指标对临界细粒含量的范围进行了预测;最大孔隙比和最小孔隙比随着细粒含量的变化反映了颗粒的形状和相互间接触关系,由此得到的临界细粒含量也是区间值;分形理论中的分维数反映了土体颗粒结构的自相似性,通过分形维数变化情况的探讨进一步缩小了临界细粒含量的取值;稳态线反映出无黏性混合土的力学性质特征,取稳态线斜率变化处的细粒含量为临界细粒含量。后两种方法得到的临界细粒含量均在前两种方法获得的区间范围内。综合各种方法,得出由南京砂重塑得到的无黏性混合土的临界细粒含量为25%。

Multi-ways to identify the transitional fine content of cohesionless soil with fines

Transitional fine content(TFC) shows that the particle size distribution and structure of cohesionless soil with fines has significant effects on its mechanical property. It is an important and difficult question to determine TFC because it is a verified process mutually. It is assumed that the cohesionless soil with fine is a dualistic structure, including sand particle and silty particle. Based on a theoretical analysis of the influence to the void ratio by the particle skeleton, the scale of TFC was determined with basic physical indicators of soil. The maximum void ratio and minimum void ratio of mixed soil with different fines change with the shape of the particles and contact relationship each other. Thus TFC is a interval value. The particle size distribution was analyzed by the fractal theory, while the fractal dimensions of mixed soil were obtained. The TFC is the place where the fractal dimension is different. Steady state line shows the liquefaction resistance of cohesionless soil in the steady-state theory. The fine content at the change of steady line slope is TFC. The results obtained by the two latter methods are in the range of the two previous methods. By there methods, TFC of the remolded Nanjing sand with different sand and silt content is 25%.