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Constant-head and variable-head injection tests for determining the hydraulic parameters of an aquitard
Hydrogeology Journal ( IF 2.8 ) Pub Date : 2020-07-16 , DOI: 10.1007/s10040-020-02186-y
Yawen Xin , Zhifang Zhou , Zhi Dou , Mingwei Li , Jun Ma

Although specific storage (SS) is a crucial parameter for characterizing the dynamic water-release process in an aquitard, the Hvorslev analysis method is only capable of estimating the hydraulic conductivity (K), rather than SS. The Hvorslev method is based on an assumption of steady-state flow and uses the falling-head test. Considering the elastic water-release effect in an aquitard and the actual groundwater flow, two mathematical unsteady-state groundwater flow models (i.e., the constant-head and variable-head models), describing the head distribution are presented for a constant-head injection test (CHIT) and variable-head injection test (VHIT) performed in a multi-layered aquifer-aquitard system. The analytical solutions for the models are derived by Fourier transforms to estimate K and SS. The obtained K and SS values from the CHIT and VHIT were generally consistent, although the VHIT is recommended in practice. For the VHIT, estimating K using the Hvorslev analysis method under steady-state groundwater flow conditions resulted in a small relative error compared to the obtained result from the variable-head model. It was demonstrated that a certain relation existed between the constant-head and variable-head methods when the drawdown rate was lower than 1%, and so the constant-head method was applied to the VHIT data to determine K and SS. The synthetic error in the parameters was smaller than 10%, which indicated that the methods could be used interchangeably under these circumstances, thus simplifying the hydraulic parameter estimation process.



中文翻译:

恒定水头和可变水头喷射测试,用于确定水准仪的水力参数

尽管特定的存储量(S S)是表征水族箱中动态水释放过程的关键参数,但Hvorslev分析方法仅能够估计水力传导率(K),而不是S S。Hvorslev方法基于稳态流量的假设并使用落差测试。考虑到无水层中的弹性放水效应和实际的地下水流量,提出了两个数学上的非稳态地下水流量模型(即恒压头和变压头模型),描述了恒压头的压头分布。多层含水层-阿奎塔尔系统中进行的气密性测试(CHIT)和可变头注入测试(VHIT)。对于由傅里叶导出的模型解析解变换来估计ķ小号小号。获得的KS S尽管实际上建议使用VHIT,但CHIT和VHIT的值通常是一致的。对于VHIT,与从可变水头模型获得的结果相比,在稳态地下水流量条件下使用Hvorslev分析方法估算K导致相对误差较小。已证实恒定头和可变头部方法之间存在一定的关系时,垂伸率低于1%,所以恒定头的方法施加到VHIT数据以确定ķ小号小号。参数的综合误差小于10%,这表明这些方法在这种情况下可以互换使用,从而简化了水力参数估算过程。

更新日期:2020-07-16
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