水分入渗条件下层状非饱和松散沉积物中的毛细壁垒效应研究  

Capillary barrier effects during the infiltration process in layered unsaturated unconsolidated sediments

作　　者：程东会[1] 钱康[1] 常琛朝 

机构地区：[1]长安大学环境科学与工程学院,陕西西安710054

出　　处：《水文地质工程地质》2016年第4期20-25,共6页Hydrogeology & Engineering Geology

基　　金：国家自然科学基金项目(41072184;41472220);中央高校基本科研业务费专项资金项目(310829162015)

摘　　要：层状结构是松散沉积物常见的沉积结构,这种结构的沉积物会表现出一些特有的水力学性质,从而对非饱和水分运动产生重大影响。本文采用砂槽二维流入渗试验,研究了层状河流相松散沉积物中水分运动规律和毛细壁垒的形成过程及其特征。研究结果表明,在上细下粗的层状结构沉积物中进行二维流入渗时,由于介质的突变导致了水分在细粒层中优先流动和贮存,下部的粗粒层起到了一定的阻水作用,从而构成了毛细壁垒。含水率是表征毛细壁垒现象的灵敏指标,而负压指标不灵敏。除了岩性差异外,粗粒层的含水率也是控制毛细壁垒形成的重要因素。在本次研究中,粗粒层含水率到达0.04 cm^3/cm^3左右时,形成了明显的毛细壁垒效应。数值模拟结果表明,在实验尺度下出现的毛细壁垒现象可以用负压水头和位置水头为主要驱动力的传统势能理论进行合理解释。Layer structure is a common geologic phenomenon in unconsolidated sediments,and some special hydraulic properties occur due to the layer structure and they can greatly affect the unsaturated water movement. In this paper,a 2-D flow infiltration experiment was carried using a sand box to demonstrate water movement and to examine the characteristics of capillary barriers in the unconsolidated sediment with layered structure. The results show that the barrier effect is achieved by a coarser-grain sediment layer underlying a finer-grain one,and the fine-grain layer exhibited priority flow and storage water while the coarse-grain layer exhibited the water-resistivity characteristics. Moisture content was sensitive to indicate the process of capillary barriers while the matrix potential was not sensitive. Beside the lithologic difference,the moisture content of the coarse-grain layer play an important role in the process of the capillary barrier formation. In this study,the moisture content in the coarse-grain layer reached 0. 04 cm3/ cm3 when the capillary barriers formed completely. Numerical simulation results showed that the capillary barrier phenomenon in this physical simulation can be illustrated using the conventional potential theory in which both capillary pressure and gravity were considered to be the dominant driving forces.

关 键 词：层状沉积物 非饱和入渗 毛细壁垒 砂槽试验 

分 类 号：P641.2[天文地球—地质矿产勘探]