Modelling of unsaturated gas flow by Thebes code: Validation tests

This paper presents the simulations replicating two well-documented benchmarks on coupled gas-liquid flow in unsaturated soil. The results serve as validation and verification of the formulation of the gas flow in unsaturated geomaterials in the newly developed THMC coupled FEM code Thebes. The paper first discusses the basis of the compositional method and the role of the dry air mass balance equation in the theoretical framework. The fundamental constitutive assumptions related to gas flow, as adopted in the Thebes code, are also discussed in details. Afterwards, the paper discusses simulation of a two-phase infiltration test in unsaturated sand, as well as a one dimensional drainage test. The numerical results of these two examples show that the code is able to capture the main features associated with the gas flow in unsaturated soil. The possible future improvements, both related to the theoretical framework and the numerical implementation, are discussed at the closure of the paper.