# Unsaturated Hydraulic Conductivity in Composite Porous Media
## 1 Introduction
The dual \(k_{\text{s}}\) and \(k_{u}\) control device with computerized data acquisition system KSAT Meter (Figure 1c) allows to record sets of readings of the tests of constant and variable hydraulic head in an integral way, covering ranges of conductivities measurement saturated and unsaturated hydraulic systems from 5000 to 0.01 cm/d. Although the automated permeameter is based on [PERSON]'s law (1856) for flow  
Figure 1: Permeameters used in the study: (**a**) falling-head; (**b**) constant-head; (**c**) automated permeameter. in porous media, it does not directly disrupt the data manufacturing process. Numerous investigations, including this study, used this mechanism to construct the matrix of \(k_{s}\) results in soils on a laboratory scale [26; 27; 28; 29; 30; 31]. There are several procedures to determine the hydraulic properties of unsaturated soils. Many of these approaches are based on stationary flow approximations by the Wooding equation [31], with multiple disk applications [32] or hydraulic pressure management multiple [33]. However, it is also possible to use transient flow analysis to estimate \(k_{u}\) in absolute ranges [34; 35; 36]. The mini-disk infiltrometer (MDI) (Figure 2) has been widely used in the experimental field to determine the unsaturated hydraulic conductivity, \(k_{u}\), of sediments and soils [37; 38]. Macropore flow is avoided in the case of MDI due to the negative potential (Mariotte barrier) applied during infiltration measurements, compared with other methodologies such as the Warrick method [39] and the Haverkamp method [40]. When looking back at the practical relevance of geotechnical problems, in most of them, it is clear that the flow occurs through an unsaturated porous medium. Even at present, geotechnical structures continue to be designed and modeled numerically with parameters based on saturated characteristics in terms of permeability. Therefore, realistic parameters to obtain the unsaturated hydraulic conductivity becomes essential. The analysis of unsaturated parameters is not conceived without the inclusion of suction. Therefore, there is a direct correlation between permeability and suction, whether imposed on a sample or existing in situ [2; 19; 21]. For this purpose, it should be noted that there is still a lack of information in understanding the flow in unsaturated soils and, therefore, quantitatively of unsaturated hydraulic conductivity values in different soil types. Many of the current technologies for soil improvement are based on the inclusion of minerals (Fe\({}_{2}\)O\({}_{3}\), CaCO\({}_{3}\), MgSO\({}_{4}\)). Even cutting-edge studies show that diatoms can become a promising methodology [41; 42; 43]. Therefore, knowing the unsaturated flow response of these materials becomes crucial within this field of study's state-of-the-art. The general objective of this investigation is projected to obtain the saturated and unsaturated hydraulic conductivity when different levels of suction are imposed, and various  
Figure 2: Mini-disk infiltrometer. materials are added to the sand base sample. In this study, the permeability characteristics are analyzed for different combinations of soils to understand the variation in the saturated and unsaturated hydraulic properties by conducting comparative experimental studies. The MDI evaluates \(k_{u}\) in granular soils with fine contents and synthetic fractions. Simultaneously, the soil permeability process in the saturated condition is evaluated utilizing conventional permeaters and the dual automated device as a numerical solution subject to analytical comparison discussions.