||Ontext of a feasibility study for geological disposal of nuclear waste, an in situ heating experiment was performed in order to study the thermo-hydro-mechanical responses of a geological barrier to variation of temperature. The experiment was carried out at the Mont Terri underground research laboratory in Switzerland. This paper presents the numerical modelling of the experiment. An elasto-plastic damage model has been used to describe the mechanical behaviour of the geological formation (a mudstone). The constitutive model is extended to the description of the thermo-poro-mechanical behaviour of saturated porous media. A finite element method with fully coupled algorithm has been employed for the numerical solution of boundary value problems. Variations of temperature, pore pressure and deformation during heating phases have been evaluated and compared with in situ measurements. The numerical modelling allows the interpretation of coupled phenomena observed in the experiment.