河南省栾川县泥石流源地土大直剪试验

Large Scale Direct Shear Test of Debris Flow Source Soil in Luanchuan of Henan

栾川县泥石流为降雨型泥石流,降水对泥石流源地土的强度影响较大。对栾川县自然泥石流土样(沟谷型、坡面型)和人为泥石流土样(矿渣)分别在天然含水量、快速饱和、饱和3 h条件下进行大型直接剪切试验,得到抗剪强度指标c、φ和强度包线与含水量的关系,以及不同含水状态剪应力与位移关系。结果表明,除矿渣粘粒含量太少,c值趋近于0外,矿渣φ和其他土样c、φ在天然含水量到饱和状态是明显降低的,饱和状态下剪应力-水平位移曲线有明显的波动,并在饱和3 h后,土样的抗剪强度进一步小幅度降低。一定条件下的前期降雨对泥石流的发生贡献很大。前期降雨充足,源地土体快速饱水,土体的抗剪强度明显降低,在重力和径流冲蚀作用下易破坏被地表水流带走。随着降雨持续,土体抗剪强度进一步降低,泥石流固体物源启动可能性增加。最后对泥石流不同固体物源类型启动难易程度进行了综合分析。

Most of debris flows are rainfall induced in Luanchuan of Henan, China. The rainfall has a greater im- pact on the strength of debris flow source region soil. The soil samples of natural debris flow（Gullies, Hillslopes） and artificial debris flow （Slag） in Luanchuan are tested with large scale direct shear apparatus under the condition of natural water content, rapid saturation and saturation for 3 hours. The relationship between c, ~p, strength enve- lope and water content, and the relationship between shearing stress and horizontal displacement under the condi- tion of different water content are obtained. The results show that, excepting the c of soil sample of slag with little clay tending to be 0, the ~ of slag sample and other soil samples＇ c and ~p are decreased under the condition of wa- ter content from nature to saturation. The curve of shear stree-horizontal displacement has a obvious fluctuation in saturated condition. After saturated for 3 hours, the shear strength of the soil samples has a slight reduction. A cer- tain condition of antecedent precipitation contributes a lot to the occurrence of debris flow. With ,the adequate ante- cedent precipitation, debris flow source region sc, il saturate rapidly, and shear strength has a significant drop that the soil is damaged by the action of gravity and erosion of runoff, taken away by surface water flow. As the rain continues, the shear strength of soil further reduces, and the risk of debris flow occurrence increases. Finally, deb- ris flow start-up with different types of solid source materials is comprehensive analyzed.