汶川震区震后土体入渗特征试验研究

汶川地震对土体产生强烈扰动,改变了流域下垫面特征,影响到流域产流过程,其中土体入渗特征是导致产流变化的基本因素。选择强震区都江堰龙溪河流域为典型研究区,采用双环法进行野外原位土体入渗试验,得出了泥石流流域不同类型土体的入渗特征。试验结果表明:(1)不同类型土体的最终稳定入渗率大小顺序依次为:林地(0.32mm/min)>草地(0.30mm/min)>耕地(0.28mm/min)>泥石流堆积体(0.19mm/min)>滑坡体(0.17mm/min)>裸地(滑坡后壁)(0.07mm/min);(2)研究区土体的稳定入渗率与孔隙度呈幂指数的正相关关系(R=0.95);前期含水率和细颗粒含量对林地、草地、耕地等土体入渗率的影响不明显,但滑坡体、泥石流堆积体、裸地等土体的稳定入渗率与细颗粒含量之间呈较强的负相关关系。细颗粒含量对土体入渗的影响远小于由根系及其腐烂空洞的影响,从而导致根系发育土体内的细颗粒含量对土体入渗影响不大。此外,土体表面结皮能显著降低研究区土体的入渗性能。

Infiltration Characteristics Experiment in Wenchuan Earthquake Zone

The soil suffered strong disturbance by the Wenchuan earthquake.It has changed the underlying surface characteristic and influenced the runoff process.The soil infiltration characteristic was the fundamental factor that changed the runoff producing.Longxi River basin in serious Wenchuan Earthquake zone was chose as the study area and double-ring devices was used to conduct the in-situ test.Infiltration characteristics in different types of soils were obtained.The results showed that the saturated stable infiltration rates of different types of soil including forest land,grassland,cultivated land,debris flow fan,landslide land and bare land were 0.32,0.30,0.28,0.19,0.17and 0.07mm/min,respectively.The saturated stable infiltration rate was closely related to the porosity with a correlation coefficient of 0.95.The fine grains and antecedent soil moisture content presented an obvious negative correlation with infiltration rates in debris flow fan,landslide land,bare land,however,they showed no significant influence to forest land,grassland,and cultivated land.Influence of fine grains on infiltration was much weaker than the root system and its rot hole.In addition,soil crust could significantly reduce the soil infiltration.