Nuclear waste problems start to rise up by the development of nuclear power plants. Many options were considered for disposal but finally it is discovered that deep repository method was feasible both for the human health and the nature. In order to avoid possible disasters, investigations have been initiated to deepen the understanding for the coupling processes of thermal, hydraulic, mechanical and chemical parameters at the near field of the waste. Numerical computation methods emerged to analyze the coupling processes then several software have been started to use. One of them is a GeoSys/RockFlow which is created to find numerical solutions for the cases of geo-system engineering. In this work, simulation results of Thermal, Hydraulic and Mechanic(THM) processes of a 2D axis-symmetric tunnel model with a heat source, are successfully obtained. Opalinus clay parameters were used to set the model inputs. Furthermore, theoretical background subjects such as coupling and radioactive waste disposal methods were mentioned too. Finally for the further usage of GeoSys/RockFlow, THM modelling manual were prepared and for the following academic works, benchmarks were generated.