Since 2000, the Deep Mixing is more and more applied for the construction of retaining structures. The working principle of a soil mix wall with a retaining function is mainly based on the development of an arching effect through the soil mix material to transmit the earth and water pressures, acting behind the retaining wall, to the steel beams inserted in the fresh soil mix material during execution. Example calculations of the arching effect in Plaxis 2D have recently been provided for soil mix rectangular panels in the BBRI/SBRCURnet Handbook - Soil mix walls, referred as the handbook in the present paper. A 2D analysis had been made in finite element calculations to verify the pattern of the arching effect. Based on a similar model, the authors analyze the development of such pressure arch in soil mix panels. The effect of the tensile resistance of the soil mix material is studied. The influences of the boundary conditions and the mesh refinement are also investigated. Finally, a comparison is made between the results of the numerical models and the analytical solutions proposed in the handbook for the structural verification of the soil mix walls with a retaining function according to the Eurocodes, the building codes for Europe.