LANDSLIDE MAPPING AND HAZARD ANALYSIS FOR A NATURAL GAS PIPELINE PROJECT

Landslide mapping was conducted as part of an integrated geohazard mapping program for a planned nearly 2000 km long natural gas pipeline across a highly seismic country in Western Asia and Eastern Europe. Given the propensity for seismic activity, seismically triggered landslides were deemed the primary geohazard of importance to the Project. Landslides were identified and characterized using a combination of desktop studies, field mapping, and field investigations (i.e., borings and CPTs). Mapping was conducted using ruggedized tablet PCs with customized ESRI ArcPad data forms to record such features. Approximately 1800 landslides were mapped within the 500 m right of way of the pipeline using a classification system based on the type of movement.

The landslide dataset collected from the mapping was subsequently used as input to a qualitative hazard assessment, which began with determining the lateral extent, basal shear depth, pipeline proximity, and activity of each landslide within 100 m of the pipeline centerline. Based on information determined from this review, the field mapping classification was updated to a project specific classification system with three mechanisms (falls, slides, and flows) and multiple types of landslides for each mechanism.

Initial screening on whether a landslide posed a risk to the pipeline was based on the mechanism of movement and pipeline proximity. At this stage, landslides were either determined to pose no credible hazard and eliminated from further evaluation or determined to pose a credible risk and evaluated further. The next stage of evaluation involved considering movement scenarios for each of the landslide mechanisms and the consequence to the pipeline of such movement. Using these movement scenarios, the potential for pipeline rupture was determined based on the position of the pipeline relative to the slide combined with a determination of whether the slide was active or not.

The result of this evaluation was to identify those landslides that posed a credible risk to the pipeline. Where space was available within the right of way, rerouting was recommended as the preferred mitigation strategy. Engineered solutions will likely be required for remaining landslides where rerouting is not an option.