## 1 Introduction  
The evaluation of one-dimensional (1D) consolidation is a common process in geotechnical engineering, especially in the design of foundations and structures on soft and highly compressible soils. One-dimensional consolidation involves the dissipation of excess pore pressures under sustained loads and, consequently, the compressibility of the soil over time [1]. In saturated conditions, excess pore pressures in soil voids respond directly to the increase in load. In contrast, in unsaturated soils, the reduction in matric suction and water retention in the soil pores play a significant role [2]. This has been widely demonstrated experimentally through 1D consolidation tests and isotropic consolidations [3, 4, 5, 6], as well as in numerical modeling to represent the transition from the unsaturated to the saturated condition [7]. In this context, constitutive models are crucial for accurately representing soil's stress-strain relationship and hydromechanical behavior under different saturation conditions and loading types [8; 9]. The Soft Soil and Hardening Soil models are widely used in numerical analyses because they represent soil plasticity and stiffness, enabling the study of settlements and deformations in soft soils [10; 11; 12]. This research evaluates both models and uses them to replicate the experimental behavior of a filtered copper tailings material subjected to one-dimensional consolidation under saturated and unsaturated conditions using Plaxis2D(r) software, 2024 version. The experimental data used to calibrate the models in this study were derived from an experimental oedometer test conducted under saturated and unsaturated conditions by [PERSON] et al. [13]. They tested tailings extracted from a copper sulfide processing plant in northern Chile, classified as low-plasticity silt according to the Unified Soil Classification System (USCS) [14], with a specific gravity of 2.97 and an initial degree of saturation of 60%. This study revealed significant changes in the solid skeleton and pore water pressure, which allowed us, through modeling, the analysis of pore pressure, deformation, and water flow under saturated and unsaturated conditions. We calibrated both constitutive models for saturated and unsaturated conditions using a single set of parameters. This evaluated the transition from the unsaturated to the saturated condition, considering the soil-water characteristic curve (SWCC). The consolidation test was simulated by applying vertical stresses ranging from 10 to 3200 kPa, including unloading phases. For each applied stress, pore pressure dissipation was considered until it reached a value of 0.1 kPa. For the unsaturated condition, initial degrees of saturation of 60% (water content of 16% according the material recovered from the filtration plant), 80%, and 99% were considered, replicating laboratory conditions using an axisymmetric model. The SWCC was used to analyze the hydromechanical behavior of the unsaturated condition, relating water content to matric suction. Additionally, the applicability of both models was validated for different saturation degrees, and initial suctions ranged from 0 to 50 kPa. This research demonstrated that the Soft Soil and Hardening Soil numerical constitutive models accurately represented soil behavior under various conditions. A higher degree of saturation in unsaturated soils increased compressibility and pore pressure, approaching saturated behavior and generating more significant deformations. It was shown that higher initial suction reduces the soil's water retention capacity, affecting its mechanical and hydraulic behavior. In saturated soils, the void ratio decreased by up to 52% compared to its initial value under a load of 3200 kPa. In unsaturated soils, a higher initial saturation resulted in more significant deformations, with differences of up to 11% between soils with 60% and 80% saturation. Pore pressure dissipation was faster in the Hardening Soil models, particularly under stresses exceeding 400 kPa.