不同击实能量下粗粒土颗粒分形特性分析

The Effect of Particle Breakage and Fractal Characteristic for Soil with Compaction Energy

击实能量荷载引起粗粒土颗粒破碎效应,采用分形理论量化破碎程度。通过室内重型击实试验,设定4种击实能量及5种含水率探究粗粒土干密度变化规律;依据颗粒筛分试验,得到击实前后颗粒粒径分布,分析粒度分形曲线特征,总结分形维数变化规律,阐释能量及含水率引起土体颗粒破碎微观机理。试验结果分析表明,标准重型击实能量作用下干密度在含水率为8%时取最大值,不同击实能量下粒度分形曲线线性关系显著,含水率影响曲线集中程度。粗粒土分形维数随含水率增加均呈先减小后增大趋势,颗粒破碎程度随击实能量增加而加剧。分形维数取极小值时含水率随击实能量增大从10%减小至8%,建议工程压实过程应控制含水量且压实能量不小于室内标准重型击实功。

Fractal theory is used to quantify the degree of fragmentation which is caused by compact energy.4 kinds of compaction energy and 5 moisture contents are set to explore the change law of dry density under different energy loaded on grained soil by modified compaction tests.Then particle size distribution before and after compaction is obtained according to the particle sieving test.Characteristics of size fractal curves are analyzed and change laws of fractal dimension are summed up according to that distribution,which is applied to explain the micro-mechanism of particle breakage caused by external energy and moisture content.An analysis of test results shows that dry density reaches maximum when the moisture content is 8%in compaction tests of standard energy.Linear relationship of grain size fractal curves,the concentration degree of which is affected by moisture content,is significant with different compaction energy.The fractal dimension of grained soil decreases firstly and then increases with the increase in moisture content and the degree of particle breakage increases with the increase in compaction energy.Moisture contents change from 10%to 8%with the compaction energy increases under the condition that fractal dimension is minimized.It is suggested that the water content should be controlled and the compaction energy should be no less than the work of modified compaction standard tests during the compacted engineering process.