Earthquake in Papua New Guinea Results in New Concept for Securing Pipelines in Ridgeline Right-of-Way: The Micropile Contiguous Wall

Abstract

Abstract On February 25 (UTC), 2018, the project, a combine of wellpads, gathering lines, transport pipelines and its facilities, sustained a Mw7.5 earthquake, and ca. 300 aftershocks, epicentered directly under the key facilities. Around 150 km of high-pressure gas and condensate pipelines were affected. A number of design and construction decisions protected the pipelines, and prevented serious damage. However, the earthquake disturbed several sections of the pipeline Right-of-Way (ROW), which subsequently required intervention and stabilization. The challenges associated with re-occupying the remotely-situated, mountainous and disturbed ROW, and safely installing stabilization structures, led to the development of a new pipeline stabilization concept: the contiguous Micropile-Wall system. The concept, leveraging tools and techniques from the tunneling industry, and practices from the Alpine region, consists of 139.7 mm micro piles, installed in 3 m joints, in rows along either side of the pipeline. Once installed, opposing rows of these micropiles are attached to each other at ground level with steel tendons. This new concept can be installed using light equipment with minimal vibration and ground disturbance. It is designed to sustain significant earthquake loads, does not retain groundwater, and is resistant to corrosion and third-party damage. This concept was developed and selected in order to repair parts of the damaged ROW and ensure pipe integrity. Future deterioration of the adjacent slopes was taken into account, but slope stabilization for several dozens of landslides was not looked into, as this would have been too large an effort considering the remoteness of the terrain, climatic conditions, safety considerations and other constraints.