In　order　to　evaluate　the　quality　of　the　synchronous　grouting　of　shield　construction　and　to　propose　the　regulation　means　of　grouting　parameters,　taking　the　coastal　sandy　soil　stratum　as　the　target,　the　model　tests　on　shield　synchronous　grouting　are　designed　and　carried　out　to　obtain　the　slurry　diffusion　laws　at　various　locations　at　the　outside　of　a　tunnel.　On　the　basis　of　calibrating　the　contact　parameters　between　particles　in　the　discrete　element　model　with　the　help　of　the　test　results,　a　continuous-discrete　element　coupling　model　for　the　shield　synchronous　grouting　is　established　to　simulate　the　process　of　filling　and　penetration　of　the　slurry,　and　to　analyze　the　main　reasons　leading　to　the　difference　in　the　thickness　of　the　slurry　layer　in　comparison　with　the　test　results,　and　then　to　optimize　the　filling　effects　of　the　slurry　by　adjusting　the　grouting　parameters.　The　results　show　that　the　particle　migration　characteristics　of　the　discrete　element　simulation　model　can　effectively　display　the　filling　and　permeation　phenomena　of　the　slurry　in　the　excavation　gap　and　the　surrounding　soil　layer.　Affected　by　the　mobility,　the　slurry　is　easy　to　gather　in　the　grouting　hole,　and　if　the　grouting　pressure　is　insufficient,　it　will　lead　to　poor　homogeneity　of　the　slurry　layer　at　the　upper　and　lower　sides　of　the　tunnel　which　are　far　away　from　the　grouting　hole.　The　filling　effects　can　be　effectively　improved　by　adjusting　the　pressure　difference　between　the　grouting　holes　of　the　shield　machine.　Affected　by　the　pressure　of　the　soil　layer,　the　thickness　of　the　slurry　layer　at　the　upper　side　of　the　tunnel　is　relatively　thinner　compared　to　that　at　the　lower　side,　and　the　slurry　at　the　lateral　side　of　the　tunnel　will　deposit　under　the　action　of　its　own　gravity,　and　shows　a　distribution　of　＇thin　on　the　upper　part　and　thick　on　the　lower　part＇.　©　2024　Chinese　Society　of　Civil　Engineering.　All　rights　reserved.