This　study　investigates　the　segregation　processes　and　impact　response　of　binary　granular　mixtures　with　identical　densities　but　different　sizes　particles　subjected　to　gravity.　Deposition　was　compared　using　discrete　element　method　(DEM)　numerical　experiment　and　laboratory　experiment　to　determine　the　material　parameters　in　the　particle　flow　code　in　three　dimensions　(PFC3D).　With　proper　material　parameters,　many　numerical　experiments　were　performed　on　an　idealized　binary　granular　mixture　avalanche　to　reveal　its　kinetic　properties,　with　a　particular　focus　on　the　results　of　the　final　run-out　distance,　fluid　velocity,　and　impact　force　exerted　on　defending　structures.　The　simulation　results　show　that　the　energy　dissipation　in　granular　avalanches　is　higher　with　uniform　particle　sizes　than　with　mixed　particle　sizes,　indicating　lesser　energy　dissipation　in　segregation　processes.　Coarse　particles　also　play　an　important　role　in　determining　the　kinetic　properties　of　binary　granular　mixture　avalanches;　specifically,　they　obviously　affect　the　maximum　impact　force　when　the　storage　area　length　is　small.　On　the　other　hand,　fine　particles　play　an　important　role　when　the　storage　area　length　is　large.　These　results　suggest　that　the　effects　of　coarse　particles　in　granular　avalanches　containing　more　than　one　particle　size　may　be　at　least　as　important.