零通量方法原位测定给水度

The Determination of Specific Yield by Using the Method of Zero Flux Plain(ZFP) in Original Position

本文简略介绍了零通量面（ＺＦＰ）方法原位测定给水度的原理、计算，并给出了在银北平原江南试区人工调控地下水位条件下和天津万军套洼试点天然条件下应用ＺＦＰ方法原位测定给水度的具体实例。结果表明，给水度测定值与测参历时有关，对单一岩性而言，其值逐渐增大，经过相当时间后将趋于某一稳定值，其原因是非饱和带释水存在滞后作用，所以它也是反映不同释水过程的一个参数，其值是在一个范围内变化。另外给水度测定值与包气带及潜水位变动带的岩性有关，土层质地越粘重给水度值越小，包气带释水的滞后作用影响越明显。同时，潜水位降落的起始位置不同对多层地质结构的给水度测定值影响也不同。而且给水度的测定值还与潜水埋深及包气带土壤剖面初始含水量有关。

This paper presents the principle and calculation about the method of ZFP in original position and its applications examples,which are in Yinchuan Plain under the condition of artificially controlled groundwater table and in Tianjia low land under the condition of natural movement state.The results show that the specific yield determined for single lithologic soil is related to the time of determination and its values gradually increase with time until a stated value appears because of the hysteresis of dehydration in the unsaturated zone.Hence the specific yield is also regarded as a parameter for reflecting different dehydration processes but its values change within a suitable range.In addition,the values are related to groundwater tables and lithologic character,which suggests that the more viscous the lithologic character is,the lower value is and the more evident the bysteresis is during the dehydration in the unsaturated zone. What is more, the start position groundwater decline has influence on the values in multiaquifer formation,and the values are also related to the buried depth of groundwater and the initial soil moisture content in the soil profile.