Porous Medium Typology Influence on the Scaling Laws of Confined Aquifer Characteristic Parameters

Abstract

An accurate measurement campaign, carried out on a confined porous aquifer, expressly reproduced in laboratory, allowed the determining of hydraulic conductivity values by performing a series of slug tests. This was done for four porous medium configurations with different granulometric compositions. At the scale considered, intermediate between those of the laboratory and the field, the scalar behaviors of the hydraulic conductivity and the effective porosity was verified, determining the respective scaling laws. Moreover, assuming the effective porosity as scale parameter, the scaling laws of the hydraulic conductivity were determined for the different injection volumes of the slug test, determining a new relationship, valid for coarse-grained porous media. The results obtained allow the influence that the differences among the characteristics of the porous media considered exerted on the scaling laws obtained to be highlighted. Finally, a comparison was made with the results obtained in a previous investigation carried out at the field scale.

Use of fractal models to define the scaling behavior of the aquifers’ parameters at the mesoscale

“…The graph of this figure shows also the experimental law obtained from Fallico et al (2020), described by the relationship (26), and the law described by the relationship (13), according to the model of Muller and McCauley (1992), for values of k min /k max equal to 0.01, 0.03, 0.05.…”

“…Moreover, for each slug test the corresponding value of the radius of influence (R) was identified and, taking this as scale parameter, the scaling behavior of K was verified, identifying for each configuration the corresponding scaling law, according to the model of power type expressed by the relation ( 7). The values of K, R and parameters a and b of the scaling laws, obtained according to the relation ( 15), are reported in a previous study of Fallico et al (2020), to which reference is made for brevity. The scaling behavior of the actual porosity was also verified for each injection volume, taking the radius of influence as scale parameter and identifying the corresponding scaling laws.…”

“…Afterwards, taking the actual porosity as scale parameter, the scaling laws of K relating to each input volume were identified. The values of the parameters a and b of these scaling laws were obtained, on the basis of relation ( 15), according to what is set out in the study of Fallico et al (2020), to which reference is made for further information, and the corresponding values are as follows:…”

“…The experimental device used in the present study was built in the Laboratory of Hydraulics of the Department of Civil Engineering of the University of Calabria (Italy). An accurate description of the device in question is reported in numerous studies in the literature (Fallico et al 2018(Fallico et al , 2020Aristodemo et al 2018), therefore only the main construction features of the device are mentioned here. The artificial aquifer was realized inside a steel box, with square base, a side equal to 2 m and 1 m height, with suitable lateral stiffeners.…”

“…For further details, see the study of Fallico et al (2020).The porous media in question can be defined as coarse grained, with a prevalent content of sand and a not negligible amount of gravel. Furthermore, it should be specified that the porous media used here can be considered homogeneous as regards the composition, meaning that the percentages of sand and gravel highlighted above are kept constant in the entire volume of the aquifer considered, while it can certainly be considered heterogeneous in relation to the size, shape and arrangement of the grains.…”