The storage and disposal of high-level nuclear waste has been an increasing concern of the public. The deep geological disposal of high-level nuclear waste is chosen as the most favourable disposal strategy.Various mock-up tests have been carried out to fully understand the engineering barrier behaviours under complex conditions in the near field.In this report, a small scale mock-up experimental study is introduced.This is an infiltration test with the Beishan granite boundary surrounding GMZ bentonite sample carried out in the geotechnical laboratory of Tongji University. The BBM model has been intensively used to simulate underground disposal of radioactive waste. It is combined with an appropriate retention curve for bentonite materials, and it has been incorporated in THM coupled formulations.To better describe the expansive clay materials, the double structure framework,the microstructure and the macrostructure, was put forward to describe the unsaturated expansive soil behaviour. In particular, the mechanical model Barcelona Expansive Model (BExM) has been developed in UPC. With the double structure method embedded in the finite element method software Code_Bright, the hydro-mechanical experiment was modelled. From simulations, hydraulic and mechanical results were obtained. For the hydraulic part, calculated suction and humidity results were compared with measured data. For the mechanical part, the axial swelling stress and the radial stress were obtained both as numerical calculation and measurements. The macro and micro-porosity evolutions were analysed to observe the changes of the double structure level during the hydration process. With the double structure model, the numerical modelling successfully described the hydro-mechanical behaviour of the GMZ bentonite confined in a granite boundary.