After a period of heavy rainfall, the landslide of a mass of residual soil in the side slope to the Pipeline Range of PETROBRAS occurred, in which two oil pipelines and gas pipeline connecting a terminal to a refinery.
On the day following the event in field inspection performed by the TRANSPETRO team, it was found that due to the landslide, the gas pipeline was exposed, with a Section of approximately 8.0 meters apparent in a slope at risk of undergoing deformations with the movement of unstable soil.
In the course of the inspection several indications soil movement were observed, such as cracks in the ground, breaks and located cracks in reinforced concrete structures of the drainage system. Surge flow of water or soil saturation was not found, despite the high rate of rainfall during the period. Thus one ruled out the possibility of the presence of a high water table which could have caused sliding. It is assumed that this may have begun on lower slopes due to deficiencies in the surface drainage system, which caused the accumulation of rainwater and its collapse. Hence, ruptures allegedly have occurred progressively upstream until it reaches the side of the pipeline range.
To ensure the integrity of the gas pipeline and operational safety and prevent the evolution of the incidents with more serious consequences, a contingency group responsible for coordinating emergency actions to contain the slope and protecting the pipeline exposed was called.
The first actions consisted of protecting the slope using a plastic tarpaulin to prevent the infiltration of more rainwater, metal profile riveting to contain side soil movement to the pipelines and finally to the implementation of contention with soil nailing technique with shotcrete on the surface of the slope where the pipeline was exposed found. Repairs to the surface drainage system of the range and slopes, which had been damaged during landslide were made.
In parallel to emergency actions, a campaign of geotechnical surveys using Standard Penetration Test (SPT) aiming at providing grounds for stability studies for the preparation of final stabilization project of the slope.