Shock loss occurs when there is a change in the area of a drift or airflow direction. These shock losses accumulate throughout the ventilation system and will increase the mine resistance as underground development deepens or becomes more complex. Hence, shock losses should be carefully considered when establishing the resistance through a series of branches as they can be a significant contributor to the estimated mine resistance. Using computer software to simulate a ventilation system is common but applying reasonable shock loss factors in the software is not a simple or direct process. Determining shock loss values includes the consideration of historical measurements, application of factors and formulas from literature based on the geometry and complexity of junctions, and the geometry variation at different locations. For example, the shock loss at the bottom of a ventilation raise can be comprised of a 90° bend and a sudden area change. This paper presents an approach for estimating shock loss factors near raise junctions using computational fluid dynamics. Current and future work will also be compared with field measurements. Results from this approach are compared with software defaults as well as classical techniques in published literature and standards.

Large-opening stone mines are characterized by entry sizes twice or thrice the size of typical underground coal or metal/nonmetal mines. Due to the large openings, the volume of air needed to ventilate these mines is significantly higher than in coal or metal/nonmetal mines. This leads to low air velocities with low static pressure drop. Airflow in the mine mostly relies on natural ventilation and auxiliary fans at the working face. The National Institute for Occupational Safety and Health (NIOSH) is conducting research on the ventilation of large-opening stone mines to reduce worker exposure to dust and other contaminants such as diesel particulate matter (DPM). To understand airflow in a large-opening mine, we conducted a numerical modeling study using computational fluid dynamics (CFD). This paper presents the results from the CFD modeling of airflow in a large-opening stone mine. The CFD model is calibrated against the data previously collected at a large-opening stone mine. The team ran different scenarios with fan placement along with the movement of truck to simulate how effectively air is moving in the mine.

The ventilation of mines and underground works has been studied for more than 100 years, with extensive and rigorous results that currently aid in safely performing underground operations of different kinds and characteristics. However, the study of underground ventilation in large volumes such as caverns has seen relatively little open study, being part of engineering studies without further disclosure. In general terms, it is the final use of the cavern that determines the ventilation system to be used. In this regard, the present study is generated from the need to define elementary ventilation systems for underground caverns linked to the construction system, which allows for maximum pollutant drag with minimum flow rate and reducing recirculating secondary flows. For this, Computational Fluid Mechanics is used as a simulation and analysis tool through the Ansys Fluent software, generating various simulation scenarios of steady and transient flows. The results show different ways of ventilating according to the established boundary conditions and the construction geometries used, which could help to orientate future ventilation designs from an academic exercise.

Vale's Coleman mine, operating at depths reaching 1,850 m, could experience underground summer temperatures >40°Cdb/28°Cwb without cooling. Through 2019-20, BBE provided EPCM for a 10.3MWR vapour-compression cooling plant that allowed 15% ambient air mixing. The footprint was restricted on three sides: two rock walls and the existing surface intake fans/heater facility. The proximity of the new system design, immediately upstream, could not impact current performance.
CFD analyses, by Flowcare, were used to ensure the 6m set-back design of eight bulk air coolers (BACs), 4 wide by 2 high, did not impact flow or pressure of the existing fan/heater, or cooled air delivery efficiency. Seasonal operation requirements, wind effects, and mitigations were considered. Configurations evaluated included: base case (no cooling plant), permutations of the BAC design, and cross winds up to 30km/h.
The CFD analyses showed negligible aerodynamic impacts and minor influence on the fan's 2kPa total pressure and 566m3/s flow; but wind effects potentially caused up to 40% cooling loss. The addition of side-shields, currently being installed, and BAC fan deflectors were shown to reduce the loss to a maximum of 6%. This paper discusses the CFD modeling, incremental design improvements, and system performance data gathered to date.