Post-mining risk management in France and multi-hazard approaches for coal mines

Abstract

After centuries of intensive exploitation of its mineral resources, French mining sites have gradually closed. However, after mine-closure and during the "post-mining" phase, numerous residual hazards can occursometimes as soon as mining works stop, or later, such as: ground movement phenomena (subsidence, collapses), rising gas, irreversible disruptions in underground water circulation induced by mining can potentially cause disturbances, both in terms of water circulation (flooding in low areas, disruption of waterway flows) and water quality (pollution).To manage hazards and risks associated with these undesirable events, the French State has several technical and regulatory tools at its disposal. These tools make it possible to compile the available knowledge on residual mining risks related to former mining sites for a given territory, to delimit the affected areas and to define the conditions of construction, occupation, and use of land as well as measures relating to the organization, use or exploitation of existing assets in a context of a sustainable land planning management. This paper presents the methodology to assess the post-mining hazards assessment. The paper also focuses on the development of new methodology for multi-hazards analysis regarding post-mining, natural and technologic hazards. The methodology analyses the hazards interactions and consequences on the environment. The multi-hazards assessment methodology consists of three steps: the identification of the singles hazards, the identification of the hazard interactions and finally the identification of the level and the consequences of the interactions. The matrix tool and interaction organigrams are used to identify the potential interactions. Three levels of interaction are considered: simple interaction, double interaction and dominos or cascading interactions. The natural and mining flooding hazard seems as the main hazard that can trigger several mining hazards: such as ground movement (subsidence, landslide, gas production, etc.).