Decline allocation strategy through geomechanical back analysis for an underground Brazil mine

As underground mines deepen, high-deformation ground conditions can arise, leading to rock mass failure mechanisms due to stress redistribution and rock mass anisotropy. The INGA underground gold mine from AngloGold Ashanti, located at (Goias, Brazil), is situated approximately 950 meters deep. High deformation associated with buckling has affected the main decline, resulting in several phases of rehabilitation. The geotechnical risk profile strategy was established to identify key factors contributing to damage in the decline and work interruptions, based on the structural analysis, mining planning, numerical modeling, and assessing gallery direction to understand the geotechnical challenges for the planned decline in 2025. Therefore, two main decline shapes were modeled: a circular layout and a directed one, which aimed to intersect the rock's failure plane perpendicularly, to enhance stability and minimize deformation risks. This paper presents the geotechnical risk profiles (as the level of the buckling damage occurrence) developed for each ramp design, incorporating a risk percentage that assists in identifying the safest and most effective ramp layout. This approach enables the planning team to make informed decisions by evaluating the potential risks associated with each design and allows them to confidently adjust the planning design layout for the decline until 2025.