准饱和多孔介质中地下水驱替速率、圈闭气体饱和度和准饱和渗透系数的关系  

The relationship between groundwater displacement rate, air-entrapped saturation, and quasi-saturated hydraulic conductivity in quasi-saturated porous media

作　　者：程东会[1,2] 李慧 王军[1] 李爽[3] 黄梦楠 马成龙 饶泽 CHENG Donghui;LI Hui;WANG Jun;LI Shuang;HUANG Mengnan;MA Chenglong;RAO Ze(School of Water and Environment,Chang’an University,Xi’an 710054,China;Key Laboratory of Subsurface Hydrology and Ecological Effects in Arid Region,Ministry of Education,Xi’an 710054,China;School of Environmental Studies,China University of Geosciences(Wuhan),Wuhan 430074,China)

机构地区：[1]长安大学水利与环境学院,陕西西安710054 [2]干旱区地下水文与生态效应教育部重点实验室,陕西西安710054 [3]中国地质大学(武汉)环境学院,湖北武汉430074

出　　处：《地学前缘》2022年第3期256-262,共7页Earth Science Frontiers

基　　金：国家自然科学基金项目(41972248);陕西省自然科学基础研究计划项目(2019JM-146)。

摘　　要：圈闭有不连续、非流动和非混溶气体的含水层,被称为准饱和含水层。圈闭气体的存在会降低含水层的渗透性能,但准饱和渗透系数、圈闭气体饱和度和驱替速率之间的关系还没有完全被理解。本文通过室内砂性介质的驱替试验开展了圈闭气体饱和度、准饱和渗透系数和驱替速率三者相互关系的研究。研究表明,虽然总体上圈闭气体饱和度随驱替速率的增大而减小,但是在高驱替速率和低驱替速率分别出现了圈闭气体饱和度不随驱替速率变化的等值区间,该“台阶”型曲线可以采用与van Genuchten曲线类似的数学模型来表征,而砂性介质的准饱和渗透系数与圈闭气体饱和度之间呈简单的线性负相关关系。这两个经验模型说明可以用驱替速率定量估算准饱和渗透系数,该关系为利用驱替速率估算准饱和渗透系数提供了理论依据。上述准饱和水力学性质为深入理解准饱和地下水水流提供了依据。另外,驱替速率与圈闭气体饱和度的关系还表明,实验室测量完全饱和渗透系数时,应以大于初始毛细上升速率的速率进行饱和,以避免介质中的空气被水圈闭。An aquifer that traps discontinuous and non-flowing air is called a quasi-saturated aquifer.The trapped air can reduce the permeability of the aquifer;however,the relationship between quasi-saturated hydraulic conductivity(K q),trapped gas saturation(S a-t),and displacement rate is not fully understood.In this study,a displacement experiment was conducted to illustrate the effect of displacement rate on S a-t and K q.S a-t was found to generally decrease nonlinearly with increasing displacement rate and remained almost unchanged at the high or low displacement rate.This S-shaped curve can be mathematically expressed by a model similar to“van Genuchten equation”.Further,a linear negative correlation between K q and S a-t was found for sandy media.The two empirical models above imply that the displacement rate can be used to estimate K q,which provides another approach for determining the K q values.These hydraulic properties provide a basis for understanding quasi-saturated groundwater flow.In addition,the relationship between displacement rate and S a-t showed that in experiments involving fully saturated porous media,the initial saturation rate should be greater than the initial capillary rise rate when measuring S a-t to avoid air entrapment in the media.

关 键 词：圈闭气体饱和度 准饱和渗透系数 驱替速率 准饱和含水层 砂性介质 

分 类 号：P641.2[天文地球—地质矿产勘探] TE357.6[天文地球—地质学]