Spalling　failure　commonly　exists　during　the　progressive　excavation　of　underground　engineering,　and　the　stepped　excavation　of　underground　mining　stope　is　rarely　simulated　in　previous　studies.　Therefore,　the　biaxial　compression　test　is　finished　by　sandstone　samples　containing　rectangular　hole　(with　different　cavity　heights),　and　the　corresponding　numerical　simulation　is　conducted　by　the　discrete　element　method.　Based　on　the　mechanical,　optical　and　acoustic　data　captured　during　the　test,　the　main　results　and　conclusions　are　as　follows:　1)　There　are　two　paths　to　activate　the　typical　spalling　failure,　the　first　way　is　caused　by　the　rapid　energy　release　(manifested　as　sudden　AE　burst),　and　the　second　way　is　that　the　released　energy　accumulates　to　a　threshold　over　a　long　period　and　finally　causes　large-scale　damage.　2)　The　relatively　larger　cavity　height　delayed　the　initiation　of　central　tensile　failure　in　the　roof　&　bottom　surrounding　rocks　and　the　spalling　failure　in　sidewalls.　3)　The　relatively　larger　confining　pressure　contributes　to　the　early　construction　of　the　spalling　failure　and　limits　the　extension　of　the　central　tensile　crack　bands.　4)　The　construction　of　spalling　failure　is　very　fast,　the　ejected　rock　plates　are　caused　by　several　rounds　of　spalling　failure,　and　the　final　V-shaped　groove　is　built　by　the　spalling　failure　and　internal　crushing　failure.