多场次降雨对崩岗崩积体细沟侵蚀的影响

Effects of repetitive rainfalls on rill erosion of coluvial deposit in granite slope collapse

崩积体是崩岗的重要组成部分,因土质疏松,极易被侵蚀。细沟侵蚀特征是探讨崩积体侵蚀机制的重要内容。采用人工模拟降雨试验,研究多场次降雨条件(1.00、1.67、2.33 mm/min分别降3次雨)对崩积体30°坡面(5m×1 m)细沟侵蚀产沙过程及发育形态特征的影响。结果表明:1)1.00 mm/min降雨强度条件下,3次降雨的后期产沙过程趋于一致,而1.67和2.33 mm/min降雨强度条件下,前2次降雨后期产沙过程趋于一致,但第3次降雨后期产沙率急剧增大;2)各降雨强度条件下,沟头溯源作用、细沟平均宽度及深度随着降雨场次的增加而增加;3)不同降雨强度条件下的细沟特征存在差异,1.00和1.67 mm/min降雨强度时,随着降雨场次的增加,坡面的细沟数及细沟密度增加,宽深比减小,但在2.33 mm/min降雨强度条件下的结果恰好相反;4)各降雨强度条件下细沟侵蚀量及其增加幅度均增大,细沟侵蚀愈剧烈。

Colluvial deposits as a part of slope collapse are the packed material under the collapsing wall,which form the collapsing wall and original mountain slope surface under hydraulic pressure and gravity.As a type of disturbed soil,colluvial deposits feature high contents of gravel,sand,and loose materials that have a weak structure,low cohesion,poor stability,and high erodibility. Rill erosion is an important factor of soil erosion. The study of peculiarity of rill erosion will be of great significance to illustration of mechanism of the erosion on colluvial deposits. We investigated the sediment yield processes and the characteristics of rill development on colluvial deposits at repetitive rainfalls. Rainfall simulations were conducted in a 5 m2（ 5 m × 1 m） test plot（ 30°） in the laboratory. Rainfall intensity ranged from 1. 00 to2. 33 mm / min. Results are shown as follows. The sediment yield processes tended to be consistent during the later stages in the three rainfalls at the rainfall intensity of 1. 00 mm / min; while at rainfall intensities of 1. 67 and 2. 33 mm / min,the consistency of sediment yield processes only occurred in the first two rainfalls,and sediment yield rate sharply increased at the later stage in the third rainfall. At all rainfall intensities,the distance of the longest rill head from top slope became short,the width and depth increased with the increasing rainfall times; the number of rills and the density increased but width-depthratio decreased with the increasing rainfall times at the rainfall intensities of 1. 00 and 1. 67 mm / min,whereas the opposite results were observed at the rainfall intensity of 2. 33 mm / min. The rill erosion volume and the contribution on slope erosion increased with increasing rainfall times at all rainfall intensities.