山前冲积扇上输气管道冲沟侵蚀分形特征

Fractal characteristics of gully erosion for gas pipelines crossed alluvial fan

冲沟侵蚀是输气管道横穿山前冲积扇的重要地质灾害之一。通过Arc GIS软件的分析功能,结合输气管道工程的现场调查,确定水系阈值,对研究区DEM数据进行提取,获得冲积扇坡度、沟网水系、汇水域的分布情况。基于此,统计分析冲积扇冲沟个数(N)与坡度(p)、沟长(L)、汇水域面积(s)之间的变维分形关系。结果表明,冲沟侵蚀与坡度(p)、沟长(L)呈二阶累积和分形分布,且分维值Dp=1.35>DL=1.23,坡度(p)对冲沟侵蚀的影响高于沟长(L);冲沟侵蚀与汇水域面积(s)呈一阶累计和分布,分维值(Ds=0.39)较小,汇水域面积(s)对冲沟侵蚀的影响较弱。这一结果为山前冲积扇输气管道运营期确定主要巡查区域提供了理论依据。

Gully erosion is one of the important geological disasters in gas pipeline across the alluvial fan.Through the analysis by ArcGIS,combining with field investigation of gas pipeline engineering,drainage threshold was determined,and information from DEM of study area was extracted,such as distribution situation of slope,gully network,watershed zone.Further more,statistics and analysis of the variable dimension fractal relationship between the number(N)of alluvial fan flows and slope(p),gully length(L),as well as watershed area(s)were conducted.The results show that it is in second-order cumulative total fractal distribution between gully erosion and slope(p),gully length(L),and the fractal dimension value D p=1.35>D L=1.23.It indicates that the influence of slope(p)on the gully erosion is higher than the gully length(L).It is in one-order cumulative total fractal distribution with watershed area(s),and the value of fractal dimension(D s=0.39)is small,so watershed area is weak to the gully erosion.The conclusion can provide reference for the main inspection area of pipeline crossed alluvial fan in operation period.