四川省石棉县2013年“7·4”泥石流沟道侵蚀特征调查及研究

Investigation on Characteristics of Gully Erosion Caused by the July 4,2013 Co-seismic Debris Flows in Shimian County, Sichuan Province

2013年7月4日20时,四川省雅安市石棉县多条沟道暴发了大规模泥石流,且该区为芦山县"4·20"地震作用区,泥石流物源丰富,其中泥石流沟道物源占总物源的64%以上。为了解研究区泥石流沟道物源的侵蚀特征,通过研究区3条典型泥石流沟(后沟、马颈子沟、熊家沟)流通区沟道剖面的野外调查数据,分析该区泥石流在运动过程中,不同剖面位置泥石流沟道的流深、侵蚀厚度与剖面距离、剖面间的相对高差、原沟道宽度之间的关系。在此基础上,首次建立基于沟道曲率半径的泥石流流向差概念,并且得到了研究区泥石流左右岸侵蚀厚度差与沟道剖面间流向差的平均线性函数系数为0.06,泥石流平均侵蚀厚度与沟道剖面坡度的平均线性函数系数为0.09。在此基础上,得到研究区泥石流平均侵蚀厚度与流深的关系为h=5Δh+1.798×10^(-15),单位距离侵蚀方量与沟道宽度关系为ΔV=6.845D^(0.625)。研究结果为对震区泥石流沟道侵蚀特征的认识提供了依据。

At 20:00 on July 4, 2013, large-scale co-seismic debris flows broke out in Shimian County, Sichuan Province. Affected by the earthquake which hit Lushan County in April, the region is stricken with abundant debris flow sources, of which the sources in debris flow gullies takes up over 64% of the total. Investigating the erosion characteristics in debris flow gullies is of crucial and imperative significance to understanding the development of debris flows in the study area. According to field investigation of the cross sections of three typical co-seismic debris flow gullies in the study area, namely, Hougou gully, Majingzi gully, and Xiongjia gully, we examined the relationship among flow depth, erosion thickness, relative height difference between profiles, and original gully width. For the first time we present the concept of flow direction difference based on curvature radius, and obtained the coefficient of average linear function between erosion thickness and flow direction difference as 0.06, and the coefficient of average linear function between erosion thickness and profile height difference as 0.09 . The relationship between erosion and flow depth is h =5Δ h +1.798×10 -15 , while thickness erosion volume per unit distance and gully width is Δ V = 6.845 D 0.625 . The research findings offer basis for understanding the erosion characteristics of debris flow gullies in the earthquake-stricken area.