Assessment of landslide hazard under combined loading

A method for assessing landslide hazard under combined loading is described. The loads are considered as pulses that occur randomly in time. The method accounts for the rate of occurrence and the duration of the loads and calculates the rate of coincidence of two or more loads. This is used to calculate the failure probability, which is equal to the probability that the load combination will exceed a threshold value during a given time period. The method was applied to a site in the Cascade Mountains of Washington. The loads considered include those as a result of gravity, pore pressure from infiltration of rainfall plus snowmelt, loss of root reinforcement through fire or logging, and earthquakes. The example demonstrates a rational approach that accounts for the properties of the loads and the different loading conditions that may be expected.Key words: earthquake, failure probability, landslide hazard, load coincidence, load combination, pore pressure, root reinforcement.