MULTIPLE LOAD CASE ON FLEXIBLE SHALLOW LANDSLIDE BARRIERS – MUDSLIDE AND ROCKFALL

It is often the case that a number of different gravity driven hazards (shallow landslide, rock slide, rockfall, small snow slides) will act at a given location, threatening the safety of people, buildings and infrastructure in the vicinity. The damage potential is realised through the pressures that can be exerted on objects during impact, which depended on the kinetics and material properties of the mass movements.

Combined shallow landslide and rockfall hazards are a common situation for unstable slopes, where the steep flanks of landslide slopes are often sources of rockfalls.

In this contribution we discuss the challenges in designing protection measures that can cope with both shallow landslides and rockfalls, each of which having a greatly differing load case. Shallow landslides impact with spreading pressures that load gradually, while rockfalls impact punctually with high velocities. We discuss the findings from a number of full scale experiments investigating each different load case, and present a finite element simulation software FARO used in the design of flexible wire protection systems. Full scale testing of both shallow landslides and rockfalls was conducted at a purpose built test sites in Switzerland.

In all 20 experiments were conducted which permitted a detailed characterisation of the flows. It was during these experiments that a flexible wire shallow landslides barrier could be developed to withstand shallow landslide impact pressures up to 200 kN/m2 , and their loading capacity observed.

Taking the same shallow landslides barrier system, it was tested under the punctual impact load case of rockfall. The unaltered shallow landslides barrier could successfully withstand 500 kJ rockfall impacts without significant damage to the system.

The findings have demonstrated the scope to apply flexible wire protection barriers to a range of gravity driven hazards offering a single protection solution for sites affected by multiple hazards.