Balance　of　the　groundwater　and　ecology　is　crucial　for　controlled　discharge.　However,　regarding　the　segments　of　tunnel　boring　machines　(TBMs)　under　high　water　pressure,　the　stability　of　the　lining　structure　is　often　reduced　by　excessive　drain　holes　required　to　achieve　this　balance.　The　large　discharge　of　pinholes　can　easily　have　severe　consequences,　such　as　the　lowering　of　the　groundwater　table,　drying　of　springs,　and　vegetation　wilting.　Thus,　in　this　study,　according　to　the　fluid-structure　coupling　theory,　a　new　drainage　design　for　TBM　segments　was　developed　by　considering　a　mountain　tunnel　subject　to　a　high　water　pressure　as　a　case　study.　The　evolution　characteristics,　including　the　external　water　pressure　of　the　lining,　discharge　volume　of　the　segment,　and　groundwater-table　drawdown,　were　investigated　via　numerical　modeling　with　drain　holes　and　pinholes.　The　results　indicated　that　the　optimal　design　parameters　of　drainage　segments　for　the　project　case　were　as　follows:　a　circumferential　spacing　angle　and　longitudinal　number　on　one　side　of　a　single　ring　of　51°　and　2,　respectively,　for　the　drain　holes　and　an　inclination　angle　and　length　of　46.41°　and　0.25　times　the　grouting　thickness,　respectively,　for　the　pin　holes.