Recycling of TBM-Excavated Materials of the Paris Basin into Technosol: A Numerical Assessment of Its Hydrological Transfer Functions

Abstract

The new face of Paris will emerge by the Grand Paris Express, a new mass transit network as part of the broader Grand Paris urban renewal and agglomeration initiative. However, this project will generate more than 45 million tons of excavated materials, still legally considered as wastes. This study is based on a scientific solution suggested for recycling those geological materials which will be excavated mainly by tunnel boring machines. The concept is to transform them into new soil called “Technosol” in the World Reference Base for soil Resources or “Anthroposol” in the French Pedology Referential. With a dedicated mode of implementation, those technosols should have interesting hydraulic, thermal, geotechnical and pedological properties. Technosols will allow to re-vegetate and minimize heat island effect and flooding hazard in urban areas, and this will bring new life to the urban ecosystem. In this study, to explore some properties of a patented technosol, COMSOL Multiphysics software is used to couple a soil hydraulic model with a thermal model of a porous medium in unsaturated state. The main result of running transfer functions through “dry” soil is production of realistic initial conditions of temperature and humidity profiles. Knowing these initial conditions and ensuring numerical stability of the model are requested for future hydrological simulations (runoff, infiltration, recharge of the saturated zone) with real material, rainfall and atmospheric temperature data.