Deep Mining

An underground mine will be considered as a deep operation if it meets any of the following criteria:

• ore is extracted at depths greater than 1000 m,
• encountering issues related to increased ground pressures such as seismicity and/or wall convergence;
• encountering issues related to increased ambient temperatures such as risk of heat stress in the workers. 

In order to mine safely and economically at depth, the Canadian mining industry faces new technical challenges to operate under these difficult conditions. CanmetMINING is addressing some of the issues through research initiatives studying seismic data analysis, engineered supports and hot environment management. 

Mine Induced Seismicity in Deep Mines

Mining affects the natural stress field of the rock mass. Stresses are redeployed after mining, in relation with rock mass parameters. Rockbursts occur when the rock mass exceed its capacity to accumulate seismic energy. As Canadian mines are going deeper, more rockburst prone areas are encountered because of stress increase with depth.

A seismic system collects data from rockbursts and mining activities. Thorough analysis of signals gives a better understanding of seismic activity at a mine and is an additional tool for mine design.

CanmetMINING has developed its expertise in mine induced seismicity since the Canada-Ontario-Industry Rockburst Project which began in 1985. CanmetMINING developed its own macro-seismic seismic system in 1990 with dual gain capability. Dual gain allows the recording of smaller seismic events as well as larger ones.

Available state-of-the-art technologies are the new components for a third generation seismic system with better recording of seismic signals at depth. New research projects are under development to better understand the effects of mining and rock mass parameters on seismic activity at depth.

Engineered Supports

The Engineered Support Group is involved in the research and development of ground support aimed at ensuring the stability of underground excavations. In an underground mine, ground support is mainly composed of various types of bolts and surface support, such as mesh and shotcrete. The mining industry now has the opportunity of choosing from many different types of support to optimize their design in order to mine in a safe and economical manner. An optimal support design will match the anticipated ground behaviour.

The Engineered Support Group has therefore developed equipments, tools and testing protocols to evaluate the behaviour of various ground supports under different conditions. The Group is actively involved with the ground support manufacturers and the mining industry to optimize new and existing ground support to be used in extreme conditions such as deep mines and weak rock masses.

Hot Environment Management

Mines are now extending to depths of 3 km as they follow the ore. Air temperatures can increase by 10°C per kilometre. This may not be an issue in winter but is a concern during summer months. When year round cooling is required, conventional surface air conditioning may not be practical.

Considerable power and cost, and significantly larger infrastructure are needed to deliver air in deep mines. Hence the importance of ensuring the ventilation is appropriate and every effort has been taken to mitigate demands.

Direct cooling of the worker also needs consideration. With increased mechanization, the mine’s workforce is shrinking while the mine is getting larger so mine-wide solutions may not be practical.

Heat Stress

Heat stress can be fatal or have serious health effects. The current methods to manage heat exposure are adequate but may not be optimum. Hence, the mining industry wants to have a better understanding of how to manage exposure.

Physiological research targeting miners and other at risk populations is providing new, important and unparalleled information of such factors, as age and health. Current mining industry demographics show an aging workforce of 40+ whereas historical research has been based on much younger personnel. Aging consequences such as type-2 diabetes and increased use of medication also affects how well humans can work in hot conditions.

More specific solutions and controls developed from this research will reduce the duty of HVAC systems enabling mines to improve their energy intensity.

Cooling Technologies

Canadian winters offer a unique cooling potential if that cold can be stored until the summer. Natural cooling options can also provide heat during the winter offsetting the need for fossil fuels. The increased use of natural cooling could significantly reduce power and refrigerant usage. As with the ventilation, managing this limited resource is critical.

Clothing also becomes important cooling consideration. This barrier between the worker and the environment controls heat exchange. Meeting safety demands, such as fire or electric arc protection, without compromising cooling is a continual challenge.