Establishing pipeline failure frequencies enables designers and operators to make informed decisions on the allocation of resources to address different threats. Normally, this would involve the selection and timing of inspection, monitoring and protection activities. Typically, failure frequencies are defined based on the collection of historical statistics. This is difficult for geohazards due to the comparatively low incident rate compared to other hazards, however the consequences tend to be catastrophic. As a result, significant uncertainties are attached to predicted failure frequencies for geohazards.
Two principal areas of uncertainty cover the occurrence and nature of loading events and whether the pipeline will survive the loading. This paper addresses both of these key aspects. The occurrence and nature of loading can be determined from the examination of in-line inspection records through different terrains. The pipeline survival rate is based on the efficient execution of multiple analysis runs within a finite element code where the distributions of the key input variables are defined to cover either observed or potential variation in the field. These include landslide size, orientation, movement and soil stiffness values as well as considerations of tensile fracture limits. The calculation of the probability of pipeline failure due to landslide loading is illustrated using a case study.
