泥石流源区宽级配砾石土渗透特性试验研究

Study on Permeability Test of Debris Flow Source Regiong Soil

对泥石流启动机理的研究表明,源地土的渗透特性具有重要的作用。通过原位双环渗水试验,对汶川地区典型泥石流沟源地土进行了原位测试,得到了初渗率与稳渗率值。对张家坪沟源地土入渗过程分析表明试样颗粒粒径较大,块石含量较多,细颗粒含量较少,孔隙裂隙较为发育,土体结构较为松散,是该区域入渗过程中达到稳定渗流的时间较长、渗透率较大的主要原因。各区域渗透系数间的差异主要由土体结构、级配特征和物质来源不同所造成。国内外相关研究根据不同土体的入渗规律提出了Kostiakov模型、Horton模型和Philip模型,使用Kostiakov、Philip和Horton三种入渗模型对入渗过程进行拟合,结果表明Kostiakov模型相关性最好,能准确的反映源地土的渗透过程；同时Kostiakov模型参数计算表明,a值在26．62~65．94之间,表明入渗过程中渗透速率衰减较快。除张家坪沟外,n值均大于0．4,表明入渗过程中土体结构变化较大,张家坪沟土体块石骨架作用较强,因此土体结构变化较小,较为稳定。

Study on starting mechanism of mudslide shows that the source region soil play an important role. Test on typical debris flow source region soil by in-situ double ring infiltration test was done in-situ and go the initial infiltration rate and the steady infiltration rate value. Zhangjiaping ditch source of soil infiltration process analysis shows that large particle size of sample,big content of stone,small content of fine particle,developed porosity and fracture and loose soil structure is the main reason of large permeability and long time to achieve steady seepage. The main difference between the permeability coefficient is because of the soil structure, gradation characteristics and sources caused by different substances. Infiltration law studies at home and abroad proposed Kostiakov model, Horton model and Philip model according to different soil. Using three infiltration model to fit infiltration process,the results show that the process are best correlation with Kostiakov model which can accurately reflect the infiltration process itself. Meanwhile Kostiakov model parameters calculations indicate that a value between 26. 62 to 65. 94, which reflect the permeation rate decrease rapidly in the infiltration process,n value are greater than 0. 4 without Zhangjiaping ditch,show that soil structure changes in the infiltration process. Zhangjiaping ditch soil’ s effect of stone skeleton is stronger,so it’ s soil structure is more stable than others.