Natural Hazards Events Identification Along the Trans Adriatic Pipeline Monitoring With Geotechnical Monitoring System

Abstract Landslides and unstable ground conditions represent a significant hazard for pipelines since they can generate permanent ground displacement (PGD) along or across the pipeline alignment. Pipeline rupture is not uncommon in incidents caused by landslides. As such, landslide-related incidents often result in leaks that may have severe environmental impact as well as long periods of operational stoppage. Regarding pipelines running through mountainous areas, statistics show that landslides are the most common cause of pipeline rupture and as such the most significant operational risk. The Southern Gas Corridor covers all infrastructure projects involved in bringing natural gas from the Caspian Sea to Europe (Fully operational since 2020). Crossing seven countries and stretching across 3,500 kilometers, the Southern Gas Corridor is one of the most complex gas value chains ever developed consisting of 3 major Pipelines: South Caucasus Pipeline (SCPX) – Azerbaijan-Georgia, Trans Anatolian Pipeline (TANAP) – Turkey, Trans Adriatic Pipeline (TAP) – Greece-Albania-Italy. The European section of the pipeline that present the highest landslide geohazard susceptibility is located in the mountainous area in Albania where the pipeline crosses one of the ridges of the Pindus mountains with adverse geological conditions and the Right-of-Way (ROW) is exposed to soil instabilities which is worsened by the high seismic activity of the wider region, for a distance of 50km long. To minimize the risk caused by these geohazards, a program of identification and monitoring of those geohazards has been established using different techniques and methods. A Geotechnical Monitoring System (GTMS) using optical fiber was implemented and operational as early as 2020. The GTMS is composed of an interrogator installed in a Block Valve Station (BVS) which monitors strain and temperature. Data are uploaded to a server which processes the strain and temperature profiles for landslide and erosion detection, alarm generation and display on a Geographical Information System (GIS). A dedicated strain monitoring cable (SMC) was laid near Panarit area as the ROW goes through a section of extremely high susceptibility. It follows the surface slope contour at a depth of maximum 3 meters while the pipeline and the optical fiber communication cable (OFCC) were derived through a micro-tunnel built 30 m below the critical slope surface. Elsewhere the system uses the OFCC which is laid near the pipeline. The GTMS reported several events as early as the end of 2021 while none of the onsite visual inspections could confirm the findings. Particular attention was then brought to these events as the passed experienced gained with the GTMS in similar installation had demonstrated a high sensibility of the monitoring technique. Finally, in April 2022 the communication system that was taking advantage of the OFCC bandwidth started to flag signal quality degradation. A complete survey of the area including the micro-tunnel and using the GTMS was conducted to identify the problem and locate its position accurately. In addition to the events previously detected by the GTMS, a large strain event was spotted in the micro-tunnel entry shaft. Based on the observation, it was decided to conduct preventive maintenance works. The pipeline was not affected while the OFCC suffered a significant damage. The communication was then rerouted, the area completely reinstated, and the micro-tunnel included in the monitoring schedule of the GTMS.