ABSTRACT
The Norwegian Public Roads Administration (NPRA), Statens vegvesen, is currently constructing the Boknafjord tunnel as part of the Rogaland Fixed Link near Stavanger, Norway (so-called Rogfast project). To aid in extending sustainable excavation at section E02, NPRA commissioned a fire risk and process impact study into currently available battery-electric to diesel articulated dump trucks. A fire risk analysis has focussed on establishing possible truck fire scenarios, including a thermal runaway of the Li-Ion battery. Analyses at Rogfast E02 by means of the Fire Dynamics Simulator (FDS) have indicated that, tenability limits for persons located in proximity of battery-electric truck fires are similar to diesel truck fires. Careful considerations in fire safety planning (e.g. rescue shelters, evacuation) are warranted in case of both truck types, in particular for large battery-electric trucks having potentially long fire durations in (remote) underground locations. In addition, a process impact analysis has been conducted by comparison of the propulsions systems of the trucks selected. First order models have been developed highlighting that, current battery-electric trucks are of comparable loading capacity to their diesel equivalents but could have a lower driving speed and thus affect truck productivity. Moreover, it is estimated that per drill-blast excavation cycle at Rogfast E02 the battery-electric trucks require battery swapping and recharging after several trips, depending on the transport distances, in contrast to the continuous operation of the diesel trucks. Overall, the risk study has concluded that while battery-electric trucks could be adopted in tunnelling, their actual application requires additional acknowledgements in both fire safety and process planning. For Rogfast E02, this is compounded by the long uphill transport task, posing challenging characteristics for the battery-electric trucks and their battery capacities. Based on the findings of this study, NPRA elected not to require the use of battery-electric trucks at Rogfast E02.
