Located in Catamarca Argentina, the Bajo de La Alumbrera open pit mine experienced a large-scale instability along its southwestern wall on May 31, 2017. Itasca performed additional numerical modeling analyses to back-analyze the 2017 instability to predict Factor of Safety (FS) contours and consider options to mine the remaining ore at the bottom of the pit.
Site modeling using DFN.lab (2021)
In Sweden, the Forsmark site, a sparsely fractured crystalline host rock, is selected to be the future location for building a deeply sited nuclear waste disposal. The definition of highly detailed, and DFN (Discrete Fracture Network) based, site models is required for both post-closure safety assessment and construction purposes. DFN-based models are considered as the most accurate representation of the fractured system and of the geological context.
Wind farm construction requires large cranes to lift massive wind turbine structures over 300 feet tall and exceeding 160 tons. Installing these structures requires many crane “walks”, moving the heavy cranes around 50 miles along soil surfaces of varying strengths. Moving the cranes quickly is critical to installation economics, but this must be done safely by ensuring soil strength stability to avoid sinking or toppling the crane. Conventional best practices require cone penetrometer tests (CPTs) and performing numerical modeling to establish a safe path for moving the cranes requires on the order of four to six weeks. Itasca developed a rapid bearing capacity prediction tool using Python scripts, FLAC3D, and machine learning to provide near real-time feedback on the soil bearing capacity at a location, allowing enhanced crane walk planning.
For pile groups with a relatively large pile cap, the geotechnical failure is generally not the controlling failing mechanism of the system. It is almost always settlements, rotation, or performance that controls the design.
In this project, the effects of deformation and rotation with regards to the pile length were observed. Specifically, four piles of a pile bridge were driven through an intermediate sandy layer and may have encountered a local anomaly (Figure 1). A safe assumption was to consider the anomaly to be clay. Additionally, the benefit of any additional helping elements to balance the stiffness distribution of the pile under the pile cap were evaluated.
In general, analysis performed on wind turbine foundations focus on the effects of the foundation’s rotational stiffness and deformation for a range of overturning moments. This project stage focused on the performance of the foundation and, given the local soil condition, its bearing capacity. To evaluate the behavior of the soil-structure interaction, a detailed numerical model of the concrete foundation and its steel reinforcement (i.e., rebar) was built and analyzed in FLAC3D.
LKAB’s Kiirunavaara Mine is a large, underground, sub-level caving mine that has been seismically active since approximately 2008. With this seismic activity comes associated vibrations. These vibrations can be felt on surface in the town of Kiruna, which is currently located close to the mine on the hangingwall side. The mine is undergoing a national permitting process concerning a desired increased production rate. An important question for this process is: will the increased production rate result in changes to vibrations in the town due to seismicity?
SKB is interested in developing a 3D discrete model to predict spalling on the excavation boundaries of underground repositories for the long-term storage of spent nuclear fuel. This project provided a quantitative assessment of modeling spalling using PFC3D to study both lab- and tunnel-scale behavior.
Long-term storage of spent fuel is critical to the nuclear energy industry. The Swedish Nuclear Fuel and Waste Management Company (SKB) is developing an approach for the storage of spent nuclear fuel in an underground repository in competent crystalline rock. In order to better understand the spalling damage process, an in-situ test involving the drilling of two boreholes was performed in Äspö diorite at SKB’s underground hard rock laboratory in Äspö. Tests and monitoring were performed on the pillar that separated the boreholes. In order to further investigate the damage process, Itasca performed numerical modeling using PFC3D and FLAC3D.
Itasca conducted a seismic performance evaluation of the trestle‐wharf section of the OPC Puerto Cortes Container Terminal, located in Honduras. A FLAC3D analysis of the soil is performed, including the piles and deck of the terminal. This is a fullycoupled, dynamic, soil‐structure, time‐history analysis that quantifies the performance and potential risks for the structure and slope. The Finn model – Byrne formulation was utilized using data from investigation boreholes.
The development and mining of a deeper seam in a coal mine, located in southern Siberia is planned. ITASCA was tasked with assessing the minimum support pressure and maximum unsupported distance between shield and coal face required to ensure stability of the roof. Also the stress state, displacement field and excavation damaged zone in the roof of the seam were analyzed.
For over five years, Itasca Chile SpA (Itasca) has developed and continuously updated, the 3D numerical groundwater flow model for this open pit mine in Chile. The model is primarily used to estimate pore pressure distributions for past, present, and predictive stages of the pit excavation. These are subsequently used for 3D slope stability analysis. With the new and updated model, new predictions for future stages were made, and new mining and drainage plans were evaluated from a hydrogeological point of view.
At Troy Mine, a progression of pillar failures led to surface subsidence. Itasca back-analyzed this behavior, using a large-scale numerical model, to understand the level of stresses and failure mechanism leading to the collapse of some pillars. Forward predictions on pillar stability in another nearby deposit, in a similar geomechanical setting, were also done.
The development of a subsea tidal turbine requires specific research work concerning the design of the foundation in contact with the seabed. This design stage can be simplified by the use of numerical modelling and more particularly by using discrete modelling. HydroQuest asked Cathie Associates to check their previous calculations regarding the behavior of a single steel foundation pin in a granitic rock mass by using Itasca’s discrete numerical approach and follow the forces applied to the pin as well as the state of the damaged zone around the tip during penetration.
Itasca Chile SpA was retained to develop a numerical 3D groundwater flow model that would allow the assessment of potential environmental impacts over the aquifer due to the infiltration associated with the expansion of the Tailings Storage Facility (TSF). Additionally, it was requested to study the potential influence of infiltrations on the mine pit located about 3 km of the TSF.
As part of phase four in the extension of the ANDRA Meuse/Haute-Marne Underground Research Laboratory, a safety niche (called GT1) will be over-bored into a larger section, then extended. The tunnel axis is 16 m from an auxiliary shaft (named PX). Two perpendicular drifts, called GLN and GLE, connect these 2 excavations.