In the last twenty years, Deep Mixing has increasingly been used for the construction of retaining walls. This has become possible due to new developments in the field of mixing equipment and the composition of the injected binding agents allowing to achieve satisfactory strengths for the soil mix material. At the DFI Deep Mixing conference of San Francisco 2015, the works of the Belgian Building Research Institute (BBRI) to develop guidelines for that application were presented. This effort resulted in 2018 in the publication of the BBRI/SBRCURnet Handbook - Soil mix walls. The present keynote presents the design philosophy followed in this handbook for the realization of the soil mix walls. After presenting constructive aspects, the following design topics are particularly highlighted: the verification of the arching effect, the composite bending stiffness and the bending resistance according to the rules of the Eurocodes, the building codes for Europe. Finally, an example calculation of the moment capacity is also given.