The deterioration of berms at mining complexes occurs as a result of weather, such as rain and wind, as well as the settling of the ground. Berms also see the impact of the various equipment using them over time and are affected by outer bank instability, or undercutting.
The agency said berms must be at least mid-axle high to the largest equipment being used on the road, and larger berms may be needed for sharp turns and at steep grades. When building up berms, compaction is also important.
With earthen and broken rock berms, the agency has reminded mines to deflect tyres so that vehicles can return easily to the haul road. With berm design, the inside slope should be steep and the base width at least as wide as an axle-high berm would have.
As some mines opt to utilise boulder berms, MSHA noted that berms should be beefed up in a way that uses friction forces between the rocks and the road to impede over-travel.
Mines should also remember that more road width is typically needed to allow for the potential of the boulders being pushed by the equipment – and that, for the safety of all, the rocks should never be placed at the very edge of a drop-off.
MSHA has developed a printable poster on berm safety, and has made it available on its website.
