In　underground　engineering,　faults　significantly　influence　the　excavation　stability,　yet　the　interactive　effects　of　fault　structure　and　stress　state　on　rockburst　and　failure　mechanisms　remain　poorly　understood.　This　study　constructs　sandstone　specimens　with　prefabricated　straight,　serrated,　and　wavy　faults,　aiming　to　clarify　how　these　structures　govern　surrounding　rock　mechanics　under　biaxial　and　true　triaxial　compression.　By　employing　synchronized　acoustic　emission　(AE)　and　digital　image　correlation　(DIC)　monitoring,　the　study　characterizes　damage　evolutions　and　energy　dissipation　processes.　It　is　revealed　that　fault　structure　and　stress　state　synergistically　dictate　failure　behaviors;　concretely,　under　biaxial　stress,　straight　faults　mitigate　rockburst　by　inhibiting　the　coalescence　of　opening-orientated　tensile　cracks,　whereas　serrated/wavy　faults　induce　complex　crack　networks　that　facilitate　gradual　energy　dissipation,　reducing　abrupt　strain　release.　In　contrast,　true　triaxial　compression　enhances　shear　failure　mechanism,　intensifying　rockburst　severity　and　shifting　failure　from　unilateral　particle　ejection　(biaxial)　to　bilateral,　high-frequency　debris　ejection　associated　with　extensive　local　instability　zones　formed　by　crack　coalescence.　Acousto-optical　data　further　show　that　biaxial　compression　generates　tensile-dominated　failure,　while　true　triaxial　compression　shifts　the　RA-AF　distribution　towards　higher　RA　values,　signaling　a　transition　to　shear-enhanced　mechanisms.　These　results　highlight　the　critical　roles　of　fault-stress　interactions　in　controlling　energy　dissipation　and　crack　development,　providing　important　insights　into　fault-related　instability　mechanisms　around　the　excavations　under　high　in-situ　stresses.　©　2025