Construire sur le pergélisol. Guide pratique
The successful realization of construction projects in mountain permafrost areas is a technical and logistic challenge for all parties involved. The site selection and the structure design are of central importance. The former must be based on a detailed preliminary study which investigates whether the site is located in permafrost terrain and determines the substrate characteristics. If the site is located in ice-rich terrain, a change of location or complete renouncement should be considered. Timely observations and appropriate monitoring instrumentation at a potential construction site deliver useful information on ground temperature, ice content and deformation characteristics.
Loading conditions taking into account potential changes to the permafrost substrate must be considered for the structure design. The influences of climate change, construction activity and the use of the infrastructure can lead to permafrost degradation and for example induce differential settlement and creep. The potential evolution of the permafrost during the service life of the structure must be forecasted and the substrate characteristics chosen accordingly. Infrastructure in exposed locations can additionally be affected by natural hazards originating in permafrost areas. These must be accounted for in the hazard analyses and the residual risk determined according to the serviceability of the infrastructure. The residual risks, consisting for example of excessive loads, natural hazards and other potential risks should be communicated to the constructors. A robust, reliable bearing structure with an appropriate foundation or anchor concept and planned redundancies is essential to avoid restrictions of use during the service life of the infrastructure. Monitoring systems can be used to detect and avoid problems or hazards, thus increasing safety during all project phases. The systematic recording and analysis of measurement data can also be used as an early warning system.
This practical guideline is subdivided into three main parts. In the first part, permafrost is defined, its characteristics described and practically applicable permafrost detection techniques are presented. The central part describes a recommended project schedule. The importance of a detailed preliminary study and of an integral monitoring system during all project phases is emphasized here. In a third part, various technical solutions for foundations, anchors, excavations, flexible systems, substrate improvement, tunnels and insulation techniques are enumerated. In addition, the specific handling of building materials for infrastructure in permafrost is discussed.
Every construction project in mountain permafrost is unique and requires specially adapted solutions in order to account for the many exceptional situations which can be encountered. Due to their complexity, it is not appropriate to develop general, all-encompassing 'recipes' for sustainable construction in permafrost. These guidelines nevertheless describe various challenges and solutions, which are based on the current practical and scientific state-of-the-art regarding permafrost infrastructure, but do not claim to be exhaustive.