细粒含量P_c<25%渗透变形类型为非管涌碎砾石的颗粒级配特征及判别方法

Particle size distribution characteristics and determination method of crushed gravel with fine content P_c<25% of non-piping permeation deformation type

细粒含量判别法是无黏性粗粒土渗透变形类型主要判别方法,但细粒含量Pc〈25%渗透变形类型为流土和过渡的碎砾石,其渗透变形类型不符合细粒含量判别准则.通过对46个工程310个试样（其中Pc〈25%的试样数214个）,渗透变形试验结果统计分析发现,该类土虽然仅占同级配段（Pc〈25%）比例为6.1%,但其颗粒级配曲线均具有独特特征,即各粒径级颗粒含量均较均匀,即Cu均大于5,Cc多数为1.0~3.0之间,即该类土大多数为优良级配,进一步分析发现其D15/d85之比均小于等于5,进而提出用D15/d85≤5作为判别该类土的方法.

Fine grain content criterion is a main discriminant method for the seepage deformation type of cohesionless coarse grained soil, however the seepage deformation types of fine grain content （Pc 〈 25% ） are the soil flow and transitional crushed gravel, which do not conform to the fine grain content criterion. According to the statistical analysis on seepage deformation testing results with 310 specimens from 46 projects （in which, the number of samples （Pc 〈25% ） is 214）, although this kind of soil accounts for 6.1% in the same graded section （Pc 〈 25 % ）, the grain grading curves have such an unique characteristic that the grain content of each particle size is uniform. The values of Cu are larger than 5, and most values of Cc are within 1.0 - 3.0, so this kind of soil are mostly well-graded. Further analysis shows that the ratios of D15/d85 are less than or equal to 5, therefore the D15/d85 ≤5 is taken as a discriminant method for this kind of soil.