长江三峡库岸几何形态的分形分维研究
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摘要
利用数盒子法分段计算三峡大坝蓄水前(水位线高程约65 m)和一期蓄水后(坝前水位135 m)两个时期长江干流左右岸库岸线的分维值,并将其计算结果进行对比,以研究长江三峡库岸分维值与地质环境的关系。分析这两个时期库岸的分维值及其差值,发现峡谷区均小于宽谷区,研究表明这受库岸的地层岩性、构造、地质灾害及人类工程活动的控制或影响:①峡谷区为坚硬难风化的碳酸盐岩,而宽谷区为软硬相间易风化的碎屑岩,水流对不同软硬度岩石的侧向侵蚀差异导致库岸形态的弯曲程度不同;②峡谷区为背斜而碎屑岩区为向斜,水流切割地层的方式不同影响库岸的几何形态;③地质灾害的发生及人类工程活动影响库岸几何形态的自然发展。
We use box-counting method to calculate the fractal dimension values of left and right reservoir banks of the Yangtze River mainstream in TGP reservoir area before the water storage(about 60 m water level) and after the first-stage storage(135 m water level at the dam) in order to study the relationship between fractal dimension values and geological environment,and the fractal dimension values in the 2 periods are compared.The results show that the fractal dimension values and the fractal dimension difference of gorge area are less than those of strath area,which was affected by lithology、tectonic,geological hazard of the of banks and human engineering activities.The conclusions are as follows: ① The lithology of gorge area is carbonate rock which is hard and difficult to be weathered,while the lithology of strath area is soft and hard alternated clastic rock which is easy to be weathered.The lateral erosion abilities of flow to different kinds of rock mass leads to different bending degrees of bank shape;② The tectonic of gorge area is anticline,while the tectonic of strath area is syncline.The different cutting ways of flow to stratum affect the bank′s geometric shape;③ geological hazard and human engineering activities affect the natural development of geometric shape of the bank.
We use box-counting method to calculate the fractal dimension values of left and right reservoir banks of the Yangtze River mainstream in TGP reservoir area before the water storage(about 60 m water level) and after the first-stage storage(135 m water level at the dam) in order to study the relationship between fractal dimension values and geological environment,and the fractal dimension values in the 2 periods are compared.The results show that the fractal dimension values and the fractal dimension difference of gorge area are less than those of strath area,which was affected by lithology、tectonic,geological hazard of the of banks and human engineering activities.The conclusions are as follows: ① The lithology of gorge area is carbonate rock which is hard and difficult to be weathered,while the lithology of strath area is soft and hard alternated clastic rock which is easy to be weathered.The lateral erosion abilities of flow to different kinds of rock mass leads to different bending degrees of bank shape;② The tectonic of gorge area is anticline,while the tectonic of strath area is syncline.The different cutting ways of flow to stratum affect the bank′s geometric shape;③ geological hazard and human engineering activities affect the natural development of geometric shape of the bank.
引文
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[2]张矿.长江河道形态的分形计算[J].人民长江,1993,24(7):49-51.
[3]陈颙,陈凌.分形几何学[M].北京:地震出版社,2005.
[4]向东进,李宏伟.实用多元统计分析[M].武汉:中国地质大学出版社,2006.
[5]张芸.长江流域全新世以来环境考古研究—以长江三峡和长江三角洲地区为例(博士学位论文)[D].南京:南京大学,2002.
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