Flexible Barriers Composed of High-Strength Steel Nets, as a Solution to the Near Surface Slides

Abstract

On steep slopes, a number of different gravity driven hazards (shallow slide, rockfall, snow slides) threaten the safety of people and infrastructures. Saturated layers of soil can form shallow slides, which can trigger spontaneously and flow at relatively high speeds of up to 10 m/s (35 km/h). If a shallow slide flows into a river channel, this can spark a debris flow. Depending on the flow speed and volume of the displaced material, shallow slides can have a destructive impact, disrupting traffic routes and causing major damage to buildings. The climate as a risk factor with an expected increase in heavy rainfall in lower case alpine regions and more frequent winter storms, coupled with the fact that the snow line is moving ever higher, in the future the environment will contain more water to potentially trigger shallow slides. Meteorologists are predicting that the likelihood of extreme rainfall events will also rise across the world (global climate change). Suitable protective measures are designed to secure roads and rail lines against shallow slides. Exposed buildings must also be protected against these near surface landslips. The conventional protective measures consist in erecting structures to divert the landslide -dams or reinforced mountainside walls- requires a huge amount of constructing work. Particularly in steep terrain alongside roads and rail lines, measures like this can only be taken in certain circumstances. Flexible shallow slide barriers have been proven to retain mixtures of water and solids, such as mudslides and shallow slides, even in the event of multiple impacts. The barriers can be installed with a low outlay of material and man hours, greatly reducing costs and construction time. Combined shallow slide and rockfall hazards are a common situation for unstable slopes: the steep flanks of landslide slopes are often sources of rockfalls. Moreover, the erosive action of a shallow slide can remove soil and vegetation cover down to the underlying bedrock, exposing further potential for rockfall events. In this contribution we also discuss the challenges in designing protection measures that can cope with both shallow slides and rockfalls, each one characterized by different load cases. Shallow slides impact with spreading pressures that load gradually, while rockfalls impact punctually with high velocities. We discuss the findings of number of full scale experiments investigating different load case; a finite element simulation software FARO used in the design of flexible wire protection systems will be presented.