# Analysis of Liquefaction in Tailings Deposits by Fem Modeling of Underained Cyclic Triaxial
## 1 Introduction  
Liquefaction is a phenomenon in which saturated soils under cyclic loading lose strength and stiffness due to the generation of excess pore pressures that cause a reduction in the effective stresses of the soil [1, 2, 3, 4]. When the effective stress reaches levels close to zero, the soil tends to behave more like a fluid than a solid, losing its load-bearing capacity [5, 6]. In particular, [PERSON] and [PERSON] [7] established a simplified procedure for evaluating liquefaction, which has become a fundamental basis for the practical assessment of the phenomenon. [PERSON] [8], in turn, developed a constitutive model that couples cyclic stresses with pore pressure generation, improving the prediction of liquefiable behavior and enabling its evaluation for various geotechnical projects. More recent studies, such as those by [PERSON] and [PERSON] [9], have refined deterministic and probabilistic methods for assessing liquefaction potential through field testing. Additionally, [PERSON] [10] studied the dynamic behavior of non-homogeneous soils using experimental tests and advanced numerical simulations, which have improved the understanding and prediction of liquefaction and settlements under seismic loads. Although the evaluation of this phenomenon is complex, it is of great interest in mining tailings projects due to the unstable nature of these deposits and the catastrophic consequences of their collapse [11, 12]. The use of advanced constitutive models in the analysis of liquefaction in mine tailings is essential due to the complexity and variability of these materials. Mining tailings exhibit nonlinear mechanical behavior that cannot be adequately represented by simple models [13]. Therefore, the calibration of these advanced constitutive models using experimental tests is necessary to validate the accuracy and predictive capability of numerical simulations in cyclic liquefaction scenarios, which allows their behavior to be reliably predicted, providing a solid basis for decision-making in the design of geotechnical structures [14, 15]. Among the available experimental tests, the cyclic direct simple shear test (CDSS) offers the best representation of the in situ conditions during shear wave propagation following seismic events [16]. However, cyclic triaxial tests (CTX) stand out for their ability to simulate the three-dimensional confinement conditions observed in the field. Additionally, such tests are versatile for measuring parameters such as excess pore pressure and axial strain, which are fundamental for understanding cyclic liquefaction [17; 18; 19; 20]. Because of this, numerous studies have used CTX for the calibration of soil parameters in advanced constitutive models capable of representing the soil response under dynamic conditions [21; 22; 23; 24; 13; 25]. Existing studies are dominated by modeling using experimental tests on granular soils, which does not accurately reflect the behavior of mine tailings. To overcome this limitation, a finite-element modeling strategy using CTX tests is proposed, focusing on silt and sand from mine tailings from northern Chile, allowing a better prediction and calibration of the dynamic behavior of these materials. One of the constitutive models available in Plaxis2D(v2024.1) that is used to represent the liquefaction behavior is PM4 SAND [26; 27]. This model has been used in several studies to assess the dynamic behavior of soil [28; 29; 30; 31]. However, PM4 SAND is limited to plane strain scenarios, and therefore it cannot represent the three-dimensional stress space of a CTX test directly; accordingly, it will not be used in this paper. Meanwhile, the UBC3D-PLM model is a three-dimensional extension of the UBCSAND model [32], developed by [PERSON] [33] and later modified and implemented by [PERSON] and [PERSON] [33]. The UBC3D-PLM model is an elastoplastic effective stress model capable of simulating the liquefaction behavior of sands and silty sands under seismic loading [34].