【作者】 王平；

【导师】 胡伏生；

【作者基本信息】 中国地质大学（北京） ， 地下水科学与工程， 2010， 硕士

【摘要】 华北平原是我国政治、经济、文化和交通中心所在,也是水资源供需矛盾比较严峻的地区。该区主要供水水源是地下水。区内第四系厚度为450-600 m,自上而下分为四个含水层组,Ⅰ含水层组称为浅层咸水,Ⅱ、Ⅲ、Ⅳ含水层组称为深层淡水。深层淡水与浅层咸水构成“上咸下淡”的区域水质结构。长期超量开采深层淡水,深层水由顶托排泄转而变为接受上层水越流补给。浅层水大量混入,并未使深层水矿化度显著提高。有学者进行盐均衡分析表明,浅层咸水在越流过程中被淡化。本文旨在研究咸水渗透实验中的弥散作用,这在深层水资源开发和保护方面有重大的应用价值。通过室内试验和参数计算,研究咸水流过粘性土层时的弥散作用,为进一步研究“咸水淡化”机理打下基础。关于粘土的滤盐机理,目前有几种说法：Bredehoeft认为,带负电荷的粘土颗粒阻止阴子通过,同时阴离子对阳离子的吸引也阻止了阳离子通过,仅有离子化程度小的水分子可以通过薄膜；Hanshaw等(1973)的解释是,溶液在压力作用下通过粘土层时,粘土孔隙两端会产生电位,流出端为正极,流入端为负极,由于电荷的排斥作用,阳离子不能向流出端运动；另外还有岩土颗粒表面双电层理论等说法。本项目通过室内咸水渗透实验,研究了咸水在越流过程中与粘土相互作用的机理、过程及影响因素。咸水渗透实验模型与达西渗流实验的基本原理相同。实验所用土样分别取自河北省石家庄、曹妃甸和北京亦庄。土柱实验所用土样均经过烘干、粉碎并过标准筛,粒径<0.1 mm。同时用TST-55型渗透仪对曹妃甸采集的原状土进行渗透试验。同时绘制浓度穿透曲线并计算各土样的弥散参数。对所得结果进行分析可知,在相同的实验装置下,在本实验尺度下,渗透系数越小,流速越慢的土样,其弥散度越小。而在同样实验条件下,弥散度越小,则土样中截留所流经咸水中盐分的能力越强。本实验所用土样对水中的盐分的截留作用也解释了前人所研究的现象,即虽然在华北平原区的大尺度上存在浅层咸水向深层淡水的越流,深层淡水的矿化度却并未提高。更多还原

【Abstract】 The North China Plain is the political, economic, cultural and transportation center of China, and there are severe contradictions between supply and demand of water resources. The main water resources of the North China Plain is groundwater. The thickness of Quaternary system of this area is 450-600 m, containing 4 water-bearing layers:the first one is called shallow(superficial) saline water, and the other three layers are deep fresh water. The fact that saline water is in the superficial and fresh water is deep makes the water quality structure of this area. The deep water no longer discharged to superficial water and turned to accept the recharge from shallow water because of the long-time over pumping. The salinity of deep water did not arised although there entrained a lot of shallow saline water. The equilibrium analysis of salt shows that the shallow saline water turned fresher because of the leakage flow. The aim of this paper is to study on dispersion during saline water flow through clay-bearing soil, which is an important application of the exploitation and protection of deep water resources. Study on dispersion effect by indoor experiment and calculation and lay the foundation to study the mechanism of "the desalting of saline water".There are several theories about the desalination of soil:Bredehoeft hole the opinion that the soil partical refrained the passage of anion and, at the same time, the cation can not pass since the attraction of anion. As a result of that, only water molecule whose ionization degree is small. Hanshaw, et al. explain the fact in the other way. When solution pass through soil layer with pressure, the side of soil pore will have electric potential. The side flowing out is positive electrode and the side flowing in is negative electrode. Cation can not move to the side flowing out since the exclusion of electron charge. At the same time, there are theories of electric double layer in the surface of soil particles, et al.This paper study the mechanics, process and influencing factor of the reaction between saline water and soil during the leakage of saline water by indoor experiment. The theory of experimental model is similar to Darcy seepage experiment’s. The soil samples and core(原状土)are from Shijiazhuang and Caofeidian in Hebei province and Yizhuang in Beijing. The samples for column experiment is oven-dried, pulverised and sieved which is promised to smaller than 0.1 mm. At the same time, osmotic experiment of soil core from Caofeidian is proceeded by TST-55 osmoscope. Concentration breakthrough curve is drawed and dispersion parameter is calculated.Analyze the data from different soil samples and experiment equipment could get the conclusion that the soil samples whose hydraulic conductivity is smaller and the flow velocity in it is slower have smaller dispersivity. Under the same experimental condition, the soil samples whose dispersivity is smaller could retain more salt ions from the solution flow through the soil.The fact that soil samples in these experiments could retain salt ions also explains the phenomenon before that although in the big scale of the North China plain there is leakage flow from the shallow saline water to deep fresh water, the salinity of deep water did not arised.更多还原