Avalanche mitigation bunds
As urban development or leisure activities move into more mountainous regions, the risk posed to buildings and particularly to motorists on roads built into the mountain sides is increased by rockfalls and avalanches.
Individual boulders exposed on steep slopes can be anchored back into slopes or removed and surface debris can be contained with geosynthetics or netting, however, large-scale surface stabilisation is often not an option because of the scale of a project.
Rockfall arrest netting using high-strength tensioned wire screens and recoil braking devices to contain the impact from individual rock impacts is often used, but with that comes the requirement for routine maintenance and the clearing of debris and resetting of the fences after a rockfall which can put the maintenance team in danger.
A commonly used alternative to arrest netting is the construction of steep-sided rockfall mitigation bunds and avalanche dams. By utilising geogrids to create a steep-sided earth mass, an effective mitigation to rockfall risk can be created. The maximum impact of any potential individual rock hitting the rear of the bund can be calculated and counteracted by the dead weight of the earth mass. The rear of such bunds is typically constructed at or near vertical with a facing made from recycled tyres which help absorb the impact and protect the rear of the bund from damage due to the edges of impacting boulders. The front faces visible to the road users or the occupants of neighbouring sites being protected by the bund are typically a rock finish or a steep, vegetated facing to reduce the visual impact and to blend well into the mountain environment.
An additional advantage of mitigation bunds over rockfall netting, is that the mass not only resists the impact from individual boulders, but can also retain any fine scree, smaller stones or snow within a larger slope failure or avalanche. The bund serves as a containment dam for the fine materials and prevents roads from being blocked and reduces the threat to lives and buildings.
The dead weight of a reinforced soil bund can absorb the impact of larger boulders during a rockfall. The geometry can be suited to effectively dam large volumes of debris or snow avalanches thus improving safety and maintaining access to roads.
Functions:
- Protection
- Reinforcement
- Shock absorption
- Support of vegetation
Relevant products:
