中文摘要：

通过硬壁式渗透仪对取自华北平原典型咸淡水区域的原状土与以此制作的重塑土进行了渗透率以及化学渗透率系数σ的测定.在浓度差为0.152 M的浓度梯度下,测得原状土的σ=0.013;重塑土的σ=0.089.对两种土样来说,虽然具有同样的成分及孔隙度,但原状土的膜性能要小于重塑土.可以表明当粘土颗粒排列更加规则时,粘土会表现出更高的膜性能.在位于华北平原咸淡水典型区的衡水市桃城区,将本文确定的咸淡水界面下移情况与前人的研究进行了对比,发现下移速度较缓,考虑到该区的粘性土层具有一定的膜性能,认为该区的地下含水层系统形成了一个典型的化学渗透系统,产生的化学渗透压力一定程度的抵消了由于过采深层淡水导致的向下的水头差,使咸淡水界面的下移速率减弱.研究结果对华北平原咸水下移机理提供了科学依据.

英文摘要：

In this paper we use rigid wall permeameter to measure the hydraulic conductivities and chemico-osmotic efficiency ratiosσof the in-situ clay and derivate remolded clay from typical salt and fresh water areas in North China Plain.When the difference of concentration is 0.512 M,the values ofσare 0.013 for the in-situ clay and 0.089 for the remolded clay,respectively.In-situ clay has poorer membrane property than the remolded clay with the same components and porosity.Therefore it is inferred that clay has better membrane property when its grains have better degree of order.We measure the down shift velocity of salt-fresh water interface in Taocheng,Hengshui,which is slower than the velocity that former researchers got.We then infer that the groundwater system in this area is a typical chemical osmosis system with the membrane property of its clay layer.The chemico-osmotic efficiency partially lowers the downward hydraulic gradient and down shift of the saltfresh water interface caused by over exploitation of the deep fresh groundwater.This result would help in understanding the mechanism of the salt water down shift problem in North China Plain.