Rapid sliding and friction degradation: Lessons from the catastrophic Vajont landslide

Our back-analyzed friction - velocity relationship expands the range of velocity and displacement values that can be controlled experimentally using rotary shear tests, by an order of magnitude. With the aid of numerical analysis, therefore, catastrophic landslides can become natural experiments at the field scale that provide ultimate friction degradation values for clay filled rock discontinuities. Using the case of the Vajont landslide we find that frictional resistance across clay-filled dolomite interfaces cannot degrade to values lower than μ = 0.16.