Abstract. Transportation corridors such as roadways are often subjected to both natural
instability and cut-slope failures, with substantial physical damage to the
road infrastructure and threats to the circulating vehicles and passengers. In
the early 2000s, the Gipuzkoa Provincial Council of the Basque Country in
Spain noted the need for assessing the risk related to the geotechnical
hazards of its road network, in order to assess and monitor their safety for
road users. The quantitative risk assessment (QRA) was selected as a tool
for comparing the risk of different hazards on an objective basis. Few
examples of multi-hazard risk assessment along transportation corridors
exist. The methodology presented here consists of the calculation of risk, in
terms of probability of failure and its respective consequences, and it was
applied to 84 selected points of risk (PoR) over the entire road network
managed by the Gipuzkoa Provincial Council. The types of encountered slope
instabilities that are examined are rockfalls, retaining-wall failures, and
slow-moving landslides. The proposed methodology includes the calculation of
the probability of failure for each hazard based on an extensive collection
of field data, and its association with the expected consequences.
Instrumentation data from load cells and inclinometers were used for the anchored walls
and the slow-moving landslides, respectively. The expected road damage was
assessed for each hazard level in terms of a fixed unit cost (UC). The results
indicate that the risk can be comparable for the different hazards. A total of 21 % of
the PoR in the study area were found to be of very high risk.
Integrated risk assessment due to slope instabilities in the roadway network of Gipuzkoa, Basque Country
