一次洪水过程的泥石流物源体侵蚀机制试验

Experimental study on debris flow erosion mechanism based on a flood process

洪流是泥石流水动力条件的主要来源之一,洪流引起的沟道物源体形成的水力类-侵蚀型泥石流的形成机理较复杂,为研究一次洪水过程中,不同降雨类型对泥石流物源体的侵蚀-破坏过程的影响,利用自制大比例模型槽,通过降雨和洪水共同作用,以北京市南窖沟为研究对象,进行泥石流缩尺模型试验.通过对试验现象的观测和描述,实时记录了物源体表面在发生面蚀、坡脚掏蚀和切沟侵蚀过程中降雨量和洪水流量的变化.根据物源体不同位置的含水率仪及孔隙水压力计的测试结果,研究了泥石流物源体随降雨和洪水作用的侵蚀-破坏变化特征及机理.结果表明:一次洪水过程中,3种雨型作用下,物源体发生切沟侵蚀破坏的洪水流量均小于洪峰流量;前期降雨作用降低了物源体破坏的累计降雨量;直接暴雨作用下土体未饱和就已发生切沟破坏.试验结果为判断泥石流物源体发生破坏的降雨量和洪水量提供了借鉴,对泥石流启动过程中雨型的研究有重要意义.

The flood current is one of the main sources of hydrodynamic conditions of debris flow. The formation mechanism of the hydraulics-erosion debris flow caused by the flood current is more complicated. To study the influence of different types of rainfall on the erosion and destruction process of debris flow in a flood process, flume experiments were conducted in Nanjiao gully. The big-scale flume was made, and the artificial rainfall device as well as the rear flow device was needed. The changes of precipitation as well as flood discharge were recorded in the process of surface erosion, slope erosion and trench erosion through the observation and description of the experimental phenomena. The erosion-destruction characteristics and mechanism of debris flow were studied based on the test results by moisture content and pore water pressure at different locations of the soils. The results indicate that in a flood process the gully erosion damage occurs before the arrival of the flood peak under the three types of rainfall. The antecedent rainfall reduces the cumulative precipitation of the soil damage, and gully failure occurs before the soil is saturated with＆quot;direct rainstorm type＆quot;. The experimental results provide references for judging the rainfall and flood volume of debris flow occurrence, which has great significance for the study of rainfall pattern in the process of debris flow initiation.