This　work　proposes　a　theoretical　framework　for　the　permanent　deformation　calculation　of　unsaturated　granular　materials.　The　approach　is　based　on　the　separation　of　the　Soil　Water　Retention　Curve　(SWRC)　into　three　linear　phases.　This　representation　makes　unique　the　wetting　and　drying　paths　with　a　newly　defined　normalized　suction　s/s*.　The　same　unique　curves　of　permanent　deformations　with　the　normalized　suction　value　are　then　developed.　The　proposed　approach　is　initially　applied　to　reproduce　the　experimental　permanent　deformation　of　two　granular　materials　with　different　water　contents　on　the　wetting　and　drying　paths.　The　effect　of　the　deviatoric　stress　on　the　permanent　deformations　is　also　considered　in　the　multi-stage　loading　tests.　The　good　correspondence　between　the　predicted　and　experimental　results　confirms　the　good　capacity　of　the　proposed　approach.　Finally,　the　proposed　approach　is　injected　in　a　finite　difference　code　to　model　the　tests　performed　on　the　two　aforementioned　granular　materials.　The　numerical　simulations　show　that　both　modeling　concepts　with　variable　and　non-variable　suction　profile　predict　well　the　experimental　results　of　the　single-stage　and　multi-stage　tests.　The　maximum　deflection　of　a　typical　pavement　is　also　estimated　at　the　different　hydraulic　states,　giving　more　credits　to　the　proposed　approach.