- Tailings Dam’s Safety Assessment by Flávia Augusta Padovani, MASc., Geotechnical Consultant at BVP Engenharia, Brazil and Thiago Bretas, MSc., Geotechnical Engineer at BVP Engenharia, Brazil
During the construction and raising phases of tailings dams, excess pore pressures and localized deformations (plasticization zones) may develop due to applied overloads. Therefore, it can develop an undrained shearing in contractile materials, as tailings and foundation soils. In this case, the design of these structures must consider, in its studies, the failure by undrained shearing of the foundation as a potential trigger for static liquefaction of tailings. In Brazil, National Mining Agency – Resolution No. 13 set a minimum safety factor equal to 1.3 for stability analyzes and studies of liquefaction susceptibility considering peak undrained shear strength. In this context, the present work aims to present the safety assessment of a hypothetical tailing dam, for an undrained scenario (which was considered even for the foundation), in view of the main consolidated methodologies in the geotechnical community, for shear resistance parameters estimation. The stability analyses were developed in 2-D and 3-D, by the limit equilibrium method. The results indicated overestimated factors of safety when considering effective strength parameters for the foundation, reinforcing the importance of carefully evaluating the type of mechanical behaviour of soils under shearing.
- Stress Field Determination at Macassa Mine by Oliver Carusone, MASc., P.Eng., Rock Mechanics Engineer at Kirkland Lake Gold (KL), Canada
Oliver discusses the importance of understanding in-situ stresses for Macassa and initial attempts to measure them using overcoring. Recently, they decided to use a borehole breakout approach with an acoustic televiewer for a stress measurement program to verify the overcoring measurements. The resolved stress tensor was significantly different from what they believed it was based on the overcoring tests…
- Challenges of Tunnelling through Difficult Mountainous Conditions by Manoj Verman, Ph.D., Representative at Rocscience, President at ISRM Commission on Hard Rock Excavation
In this presentation Manoj about the challenges of tunnelling through difficult mountainous conditions.
Now, arguably the three of the most difficult tunnelling conditions in the world are posed by the Himalayas in the Indian subcontinent, the Andes in South America and the Alps in Europe. And out of these, the Himalayas offer the most challenging tunnelling conditions because they are the youngest of these mountain chains. So, as a result of that, in the Himalayas, the stress conditions can be extreme in terms of the magnitude of stresses and the variation in those magnitudes. And that can have an adverse impact on tunnelling projects through the Himalayas which can be more severe than anywhere else, including some of the landmark tunnels which are known for stress-induced instabilities, such as, Olmos in Peru in South America and Yacambu in Venezuela, also in South America. These two tunnels are known for the rockburst conditions and squeezing conditions encountered respectively.
In this presentation, Manoj talks more about squeezing and rockburst with some examples.