The　vulnerability　problem　of　expansion　joints　could　be　fundamentally　resolved　using　the　concept　of　jointless　bridges.　The　longitudinal　deformation　of　the　superstructure　can　be　transferred　to　the　backfill　by　using　the　approach　slab.　The　flat　buried　approach　slab　(FBAS)　has　been　used　in　many　jointless　bridges　in　European　countries.　In　order　to　understand　the　mechanical　performance　of　FBAS　and　soil　deformation,　a　finite　element　model　(FEM)　was　implemented　in　PLAXIS.　Considering　the　friction　between　the　FBAS　and　soil,　the　buried　depth,　the　FBAS　length　and　thickness　as　parameters,　a　parametric　analysis　was　carried　out.　According　to　the　obtained　results　and　in　order　to　reduce　the　soil　deformation　above　the　FBAS,　it　is　suggested　to　increase　the　friction　between　the　FBAS　and　sandy　soil,　and　the　buried　depth　of　FBAS.　Moreover,　it　should　be　paid　attention　to　the　vertical　soil　deformation　and　the　concrete　tensile　stress　of　FBAS　in　pulling　condition.　©　2021　IABSE　Congress,　Ghent　2021:　Structural　Engineering　for　Future　Societal　Needs.　All　rights　reserved.