粗粒土压实特性及颗粒破碎分形特征试验研究

Experimental study of compaction characteristics and fractal feature in crushing of coarse-grained soils

对多个级配不同含水率的粗粒土进行击实试验,研究粗粒土的压实特性和颗粒破碎分形特征。结果表明,粗粒土最大干密度随级配中粗粒含量的增大而增大,当粗粒含量P5=70%时,最大干密度出现最大值;当P5】70%时,最大干密度又随粗粒含量的增大而减小,粗粒土击实破碎后的粒径分布具有良好的分形特性,破碎分形维数为2.2790~2.8922,均大于击实前粗粒土粒度分形维数;相同级配条件下,粗粒土破碎分形维数随含水率的增大而增大,且粗粒含量P5】50%时,增幅显著;粗粒土破碎分形维数D与破碎率Bg存在良好的线性关系,且击实前后粗粒土粒度分形维数差值能客观表征颗粒破碎的程度;粗粒含量和含水率是影响颗粒破碎率的两个重要因素,但相对于含水率而言,粗粒含量对破碎率的影响更加显著。

Based on compaction test of different gradations and different moisture contents of coarse-grained soils,the compaction characteristics and fractal feature of coarse-grained soils are studied.The results show that the maximum dry density of coarse-grained soils would increase with the increase of coarse grained content in gradation.The maximum dry density reach the maximum value as the coarse grained content is 70%;while it would decrease with the increase of coarse grained content in gradation as the content is more than 70%.The particle size distribution of crushing granular has a good fractal feature.The crushing fractal dimensions are between 2.279 0-2.892 2;higher than that before test.Under the same gradation condition,the crushing fractal dimension of coarse-grained soils increased with moisture content.The increase amplitude is obvious when P5 is larger than 50%.A good linear regression relation exists between crushing fractal dimensions D and broken rate Bg.Difference value of the granularity fractal dimension before and after compaction can show the crushing degree of coarse-grained soils objectively.Coarse grained content and moisture content are two key factors affected on particle breakage;but the influence of coarse grained content is more obvious.