# Analysis of Liquefaction in Tailings Deposits by Fem Modeling of Underained Cyclic Triaxial
## 1 Introduction
In this paper, the UBC3D-PLM model is used to calibrate the response of silt and silty sand from tailings under cyclic loading to assess the predictive capability of the model for these types of soil. Considering that this model was developed for use with sand, this paper also intends to demonstrate its applicability to tailings silt. To perform the simulation, an axisymmetric specimen will be modeled using a fixed-frequency sinusoidal load to predict the experimental response of the undrained consolidated CTX test. The modeling used constitutive models that are included by default in the Plaxis2D(r) commercial software. The novelty in the modeling strategy was the use of two phases: (i) an isotropic consolidation stage in which the HSS model [35] was used to simulate initial stresses and confinement and (ii) a cycling stage, where the UBDC3D-PLM model was used to capture the triggering of the liquefaction response. In the calibration for the silt and silty sand tailings, the parameters common to both constitutive models were kept constant for each material since the same soil is represented at each stage to ensure consistency in the representation of soil behavior in the two modeling stages of the CTX test. Specifically, the cycling stage considered the experimental results under controlled loading with an isotropic confining stress of 100 kPa and sinusoidal loads with frequencies of 0.1 Hz for silt and 0.5 Hz for sand, with these parameters being selected to obtain the best experimental response for each soil. The calibration strategy was based on previous work with UBC3D-PLM in which the parameters were obtained from cyclic simple shear and/or cyclic triaxial tests [36; 37; 38; 22; 23; 39; 24]. The results obtained in this study were compared with the results of experimental CTX tests published by [PERSON] in 2022 [40]. These experimental results were also used to calibrate the UBC3D-PLM model, while the parameters of the HSS constitutive model for the materials analyzed in this article were obtained from [PERSON] et al. [41]. The results presented in this paper show that (a) the modeling strategy allows the excess pore pressure from experimental tests to be correctly simulated using the HSS and UBC3D-PLM models in a consolidation and cycling stage, respectively; (b) the predictive ability of the UBC3D-PLM model decreases when applying a single set of parameters at different levels of deviatoric stress, although for similar levels, the model obtained a good representation; and (c) the predictive ability of the HSS and UBC3D-PLM models in terms of effective stresses \(p^{\prime}\)-\(q\) and unit strains is limited. Given the importance of evaluating soils susceptible to cyclic liquefaction, this study presents a finite-element-based modeling strategy using UBC3D-PLM to predict the behavior of tailings sands and silts under cyclic loading in terms of excess pore pressure. This methodology offers geotechnical engineers a potentially useful tool for the design and evaluation of geotechnical projects to assess liquefaction triggering in mine tailings structures with acceptable accuracy.