pH值对红土粒度成分影响的分形几何研究

Fractal geometry research on the effect of pH on granulometric composition of red soil

红土是一种特殊土,其成分和结构决定了红土本身具有不同于一般粘性土的工程地质性质。红土中游离氧化铁的存在使土颗粒之间产生胶结,是土具有“假粉性”和“假砂性”特征的主要原因。研究发现,游离氧化铁含量和形态的改变,将直接影响红土颗粒的粒度分布。通过对不同pH值红土试样的颗粒成分进行测试,借助分形理论得到不同pH值红土粒度成分分维值。计算发现,不管是否在测试过程中采用分散剂,土粒度分维曲线上都存在两个无标度区。pH值的改变引起了土粒度分维的变化,随pH值的增大,土粒度分维值也变大,反应出土的细颗粒含量增加,土颗粒所形成的集合体越分散。土pH值的大小与粒度成分分维、游离氧化铁含量之间的内在联系,揭示出了红土中游离氧化铁对土颗粒胶结的本质。

Red soil is a kind of special soil, and its composition and structure lead to its different engineering geologic properties from common cohesive soil. The existence of dissociative iron oxide cause cementation between grains and it is the important reason of ＂artificial mealiness＂ and ＂artificial grittneess＂. Research finds that changes of contents and forms of dissociative iron oxide can directly lead the changes of granularity distribution of red soil. After grain structure analysis, using the fractal theory we get the fraetal dimension of granulometrie composition of red soil with different pH. The results show whether using dispersant or not, there are two no sign regions on the curve of grain fractal. Changing of pH causes the changing of grain fraetal, the higher of pH, the higher of grain fractal, and the more of the content of fine particle, the more divergent of grain aggregation. The inherence relationship among pH, grain fraetal and the content of dissociative iron oxide can open out the essence of cementation in grains of dissociative iron oxide in red soil.