Uso do método do ponto material (MPM) para análise de ruptura hipotética de uma pilha de disposição de estéril e rejeito

Abstract

The increasing adoption of filtered tailings stacks as an alternative to conventional tailings dams has intensified the need for tools capable of assessing not only the stability of these structures but also their post-failure behavior under large-deformation conditions. Although the Finite Element Method (FEM) is widely used in geotechnical engineering, its application to the simulation of mass movements is limited by significant mesh distortion during the evolution of failure. In this context, the Material Point Method (MPM) emerges as a promising alternative, allowing large deformations and the transport of the mobilized mass to be represented more consistently. This study aimed to evaluate the applicability of MPM in simulating the hypothetical failure of a Waste Rock and Tailings Disposal Stack (PDER), investigating the evolution of the mass movement and the runout distance of the mobilized material. As a case study, the Tamanduá PDER, located at the Brucutu Mine in São Gonçalo do Rio Abaixo, Minas Gerais, Brazil, was analyzed. A two-dimensional numerical model was developed using the open-source software ANURA3D, employing geotechnical parameters obtained from laboratory tests carried out on the tailings, waste rock, and foundation materials. Initially, the stability condition of the stack was verified using the design parameters. Subsequently, three hypothetical failure scenarios were evaluated, representing progressive levels of degradation of the geotechnical properties: (A1) reduction of the strength and stiffness parameters of the starter dyke; (A2) maintenance of the dyke degradation combined with a reduction in the strength and stiffness parameters of the tailings; and (A3) combined degradation of the starter dyke and waste rock, representing the most critical condition analyzed. The simulations reproduced the formation of the failure surface, the temporal evolution of displacements, the velocity fields, and the final runout distance of the mobilized mass in three representative sections of the stack. The results showed that the progressive degradation of the geotechnical properties led to a significant increase in the mobilization of the mass, with substantial increases in displacements, velocities, and runout distance, reaching approximately 162 m in the most critical condition analyzed. The results demonstrated that MPM adequately represents mechanisms associated with large deformations and post-failure behavior, allowing the continuous evolution of the mass movement to be tracked. It is concluded that the Material Point Method is a robust tool for analyzing hypothetical failures of filtered tailings stacks, enabling the estimation of the propagation of the mobilized mass and supporting risk assessment studies and the planning of mitigation measures. In addition to demonstrating the applicability of MPM to a real mining case, this research contributes to expanding its use in Brazilian geotechnical engineering by proposing an analysis methodology based on progressive degradation scenarios of the materials composing the stack.