The　trapdoor　test　has　been　widely　used　to　study　engineering　scenarios　where　pressure　calculation　methods　need　to　be　re-evaluated　due　to　relative　soil　displacements.　To　propose　a　more　reasonable　calculation　theory,　over　the　past　few　decades,　researchers　have　primarily　focused　on　understanding　soil　deformation　mechanisms　and　stress　evolution　on　the　surface　of　the　trapdoor.　However,　the　limited　availability　of　experimental　data　has　hindered　the　development　of　a　universally　accepted　theory.　In　contrast,　FEMs　offer　a　powerful　tool　for　capturing　more　comprehensive　and　precise　stress-strain　information.　In　this　study,　various　active　trapdoor　models　were　established,　each　with　a　width　of　2　m　and　differing　burial　depths,　using　the　FEM.　By　integrating　the　ground　reaction　curve,　the　normalized　stress　distribution　on　the　trapdoor　was　analyzed　to　reveal　significant　stages　in　soil　stress　evolution.　Additionally,　the　Mohr-Coulomb　failure　criterion　was　applied　to　differentiate　between　sliding　and　failure　surfaces,　shedding　light　on　the　evolution　trend　of　the　failure　surface.　Moreover,　three　lines　and　four　points　were　selected　to　monitor　the　evolution　of　principal　stresses　in　the　soil.　Drawing　on　principles　of　plane　strain　mechanics,　the　distributions　and　evolutions　of　the　three　principal　stresses　were　presented　in　the　xy-plane　using　vector　graphics.　Notably,　this　study　highlights　the　crucial　role　of　the　intermediate　principal　stress　in　soil　arch　calculation　theory.　©　2024　American　Society　of　Civil　Engineers.