云南永胜古滑坡堰塞湖沉积物粒度多重分形特征及其指标适用研究

Multi-dimensional fractal characteristics of ancient landslide-dammed lake sediments at Yongsheng County of Yunnan Province and its indicators applicable to research

本文以云南永胜县下院滑坡堰塞湖沉积物为研究对象,依据粒度测试结果采用传统粒度指标与分形理论相结合的方式对其沉积环境进行系统化研究,探讨各传统指标在堰塞湖沉积解析中的适用性,探索多重分形理论在沉积学中的应用价值。研究结果表明:①堰塞湖沉积物粒度统计参数明显不同于其他环境下的沉积物,具有河湖相沉积独特的分布曲线形式、分选状态和分形特征。优势粒级在分形计算中起主导地位,全局分形维数与分选系数有着良好的对应关系。不同的分形维数对应着不同的堰塞湖沉积条件,分形维数在堰塞湖粒度解析中有着很好的运用前景;②多重分形结果显示2种不同时期的堰塞湖沉积物均以高聚集度组分为主体,表明粒径分布集中,反映出堰塞湖沉积过程中水动力的稳定性,沉积来源的唯一性,进一步证明了该堰塞湖曾长期存在。细粒组沉积粒径分布范围较窄,分布相对集中,优势粒组多但单个含量低,尾端含量低,内部分异较大;粗粒组分布呈局部集中整体分散的趋势,高聚集度粒组数量少但含量高,低聚集度粒组数量多但单个含量低,呈现中间高,四周低的特点。③多重分形分析表明Δα、Δf在沉积物粒度分析中能够解析粒组内部分布特征,具有传统指标不可替代的作用,D_(0)和D_(1)两者结合可作为沉积环境解析的替代指标,与其他q阶多重分形联合可进一步作为堰塞湖解析指标,而D_(1)/D_(0)和D2则存在一定局限。

In this article,based on the results of grain size measurements,the sedimentary environment of the dammed lake formed by the Xiayuan landslide in the Chenghai-Binchuan fault zone,an area prone to frequent earthquakes,is analyzed using graphic methods and fractal theory.The study discusses the applicability of traditional indices in the sedimentary analysis of dammed lake and explores the potential value of multifractal theory in sedimentology.The results indicate that:1)The grain-size statistical parameters of sediments from the dammed lake exhibit distinct differences compared to those formed in other environments.They show unique distribution curves,sorting states,and fractal characteristics typical of fluvial-lacustrine sediments.The dominant grain size significantly influences the fractal calculations,with the global fractal dimension correlating well with the sorting coefficient.Different fractal dimensions correspond to varying sedimentary conditions within the dammed lake,suggesting that fractal dimension has promising applications in grain size analysis of dammed lake.2)The multifractal analysis reveals that sediments from the dammed lake,observed in two distinct periods,are characterized by a high aggregation of components.This indicates a concentrated grain size distribution,reflecting the hydrodynamic stability of the dammed lake during sedimentation and the distinctiveness of the sedimentary source,which further supports the notion that the dammed lake has been in existence for an extended period.The sedimentary grain size distribution of the fine grain group is narrow,with a relatively concentrated distribution.Although there are many dominant grain groups,each has a low individual content,low tail content,and significant internal variability.In contrast,the distribution of coarse grain groups shows low concentration and high dispersion.High aggregation grain groups are few but have high content,while low aggregation grain groups are numerous but have low individual content,displaying a pattern of high concentration in the center and low on the periphery.3)Multifractal analysis indicates thatΔαandΔf are effective for analyzing the internal distribution characteristics of grain groups in sediment size analysis,providing insights that traditional indicators cannot replace.D_(0) and D_(1),when combined with other q-order multifractals,can serve as alternative indices for sedimentary environment analysis,while D_(1)/D_(0) and D2 are less applicable.