连续分布超径粗粒土的级配缩尺方法与适用条件

A gradation scale method for continuously distributing super-diameter coarse-grained soils and its application conditions

结合国内若干座典型高坝,分析堆石料和砂砾料的填筑级配特性;在此基础上,结合大石峡和长河坝坝料室内相对密度试验和大型压缩试验,研究超径粗粒土级配缩尺方法的合理选择问题。结果表明:(1)Weibull模型对于反映筑坝粗粒土的级配构成具有较好的适应性,也可以反映级配的分形特性;(2)连续分布的粗粒土级配,剔除法、等量替代法、相似级配法等常见缩尺方法可采用统一的级配缩尺公式表示,可以准确计算缩尺试验级配;(3)使用最优颗粒充填关系对应的临界P5值,代替规范建议的小于5 mm颗粒质量百分含量P5不大于15%的标准,作为相似法的使用条件,即可避免过度使用混合法带来的缩尺试验误差,也不会出现相似法导致缩尺级配的'砂化'问题,可最大限度地保证缩尺前后级配的几何相似,有效提高缩尺试验结果的精度;(4)利用临界分形维Dc与最大粒径无关的性质,对于不同分布类型级配的超径粗粒土,可采用分形级配公式计算缩尺级配的临界P5值,并根据原级配参数确定相应的缩尺方法。研究成果可用于超径粗粒土的缩尺试验,具有较强的应用价值。

Based on several typical high dams in China,the grading characteristics of rockfill and gravel were analyzed,and soil grade reasonable scale method of the super-diameter coarse particles was studied combined with the indoor relative density test and large compression test of Dashixia and Changheba dam materials.The results show that Weibull model can well reflect the gradation and fractal characteristics of dam coarse-grained soils and that common scale methods such as knockout method,equal replacement method and similar grading method can be expressed by a unified grading scale formula to accurately calculate the scale test gradation based on Weibull grading model.Using the critical P5 value corresponding to the optimal particle filling relationship as the condition of the similar scale method instead of less than 5 mm particle mass percentage P5 not more than 15%recommended by codes,the scale test error due to excessive use of the mixing method can be avoided and the scale grading'sanding'problem can also be eliminated.At the same time,the geometric similarity of the grading can be ensured and the accuracy of the scale test results can be improved effectively.For the super-diameter coarse-grained soil with different distribution types,based on the property of the critical fractal dimension Dc independent of the maximum particle size,the critical P5 value can be calculated by the fractal grading formula and the corresponding grading scale method can be directly selected according to the parameters of the original graded soil.The research results can be used for the scale test of super-diameter coarse-grained soil and have strong application value.