Practical aspects of the ventilation of high-speed developing tunnels in hot working environments

Abstract

The excavation of ramps and tunnels often requires high-speed development with [or without] the use of high-energy mining equipment such as loaders, dump trucks, TBMs and roadheaders. This highspeed development creates a challenge in terms of providing a safe and productive working environment. For example, heat from continuously exposed surrounding rock, heat from broken rock, heat generated by mining equipment, potential inflows of hot ground water, pollution from associated diesel equipment, and the distance of the advancing face from fresh through-ventilation all have to be taken into account when designing ventilation systems for high-speed ramp and tunnel developments. This paper discusses methods of achieving acceptable environments at the face and along the length of the tunnel. The methodology has been successfully implemented in the development of long [up to 20 km] TBM drives in the Lesotho Highlands Project and in mining projects in hot rock using drill-and-blast methods as well as in mechanised methods using continuous miners and roadheaders. The determination of heat loads includes calculation of the heat flow within the surrounding rock, evaluation of the operating cycle of the equipment and the contribution to the overall heat load of the broken rock as it travels out of the tunnel. The determination of heat loads from surrounding rock in new tunnels required a modification of the algorithms generally used for established excavations. The paper also examines the use of, for example, mobile duct and fan systems to ensure that fresh air is delivered to the specific areas where workers are located.