Post event site investigation, monitoring, stability analysis and modeling of a gas pipeline explosion

This paper describes the results of site investigations, monitoring, stability analyses and soil-pipe interaction modeling of a built-up slope located near Pineto (Abruzzo Province, Central Italy) where a gas pipeline exploded on March 6th, 2015 due to heavy rains inducing slope movements. The slope is formed by OC clay, covered with an upper 10-14 m thick clayey-sandy silt colluvial layer. The explosion in the upper portion of the slope caused extensive damage to existing buildings and threatened human lives. Soon after the event, a site investigation and monitoring program was carried out. A detailed topographic survey and hydrological data were analyzed in order to characterize possible critical rainfall events. The stability of the slope was analyzed both in pre- and in post-explosion conditions. The profiles of the DMT horizontal stress index KD helped to identify multiple slip surface. Then, the results of the site investigation and stability analyses were used to implement a simplified finite element model aimed to describe the soil-pipeline interaction, taking into account the role of the observed wrinkle in the pipeline. The numerical simulations reveal the crucial role played by the slope movements, and by the wrinkle as well, in inducing the collapse of the pipe.