In this thesis the first steps in the verification process of the new Thermo-Hydro-Mechanical (THM) kernel of PLAXIS are made. The proper implementation of the governing equations is verified by comparing model output with analytical solutions. Good agreement is obtained for thermo-mechanical problems. The governing equations for a full THM study are coupled and non-linear. Because of this analytical solutions are only available when approximations are made. An exact solution is presented for the advection-diffusion equation of temperature. The implementation of the vapor diffusion is investigated. The model CODE_BRIGHT developed at the University of Catalonia (UPC) has been matched with experimental results. By matching the model output of PLAXIS with CODE_BRIGHT it will be possible to obtain similar agreement with experimental results. Good agreement between PLAXIS and CODE_BRIGHT is demonstrated by doing a numerical comparison.