A　novel　spatial　soil　arching　(SSA)　effect　and　the　arching　mechanisms　and　characteristics　of　a　steep-slope　high　embankment　in　a　double-V　narrowing　gully　(DVNG)　were　investigated.　First,　the　consistency　between　the　results　obtained　via　a　lab-scale　experiment　and　the　three-dimensional　finite-element　model　(FEM3D)　confirmed　the　existence　of　SSA　in　the　DVNG　(DVNG-SSA)　and　validated　the　numerical　model　feasibility.　The　enlarged　FEM3D　revealed　that　the　DVNG-SSA　was　generated　by　stress　redistribution　caused　by　uneven　soil　displacement.　Moreover,　the　DVNG-SSA　could　generally　be　divided　into　horizontal　(H-)　and　vertical　(V-)　DVNG-SSAs,　which　could　interact　with　each　other　to　form　large-scale　spatial　soil　arches　at　the　front　and　bottom　of　the　embankment.　Parameter　sensitivity　analysis　revealed　that　increasing　the　Poisson＇s　ratio　of　the　soil　negatively　affected　both　arches.　The　H-DVNG-SSA　only　had　side　banks　acting　as　arch　feet,　while　the　V-DVNG-SSA　had　an　additional　ditch　bottom.　Compared　with　H-DVNG-SSA,　V-DVNG-SSA　had　a　broader　range,　flatter　shape,　longer　length,　deeper　thickness,　lower　height,　and　smaller　maximum　rise-span　ratio.　Finally,　the　strength　of　the　DVNG-SSA　was　lower　than　that　of　the　conventional　pile-soil　SSA　despite　its　extensive　coverage,　which　could　considerably　impact　the　overall　embankment　stability.　©　2023　American　Society　of　Civil　Engineers.