The　dynamic　behaviour　of　cross-tunnel　structures　under　the　wheel-rail　impact　forces　of　heavy-haul　trains　is　complicated.　This　paper　establishes　an　impact　force　excitation　input　model　to　simulate　the　wheel-rail　vertical　forces　of　rail　welded　joints.　The　calculated　results　of　the　correction　formula　of　wheel-rail　vertical　forces　for　seamless　rail　joints　are　in　good　agreement　with　the　measured　data　and　meet　the　accuracy　requirements.　The　present　paper　describes　a　1/50　scale　model　experiment　based　on　the　case　of　the　newly-built　Jing-Zhang　Railway　underneath　the　existing　Tang-Hu　Heavy　Haul　Railway.　Numerical　simulation　analysis　uses　FLAC3D　to　simulate　the　experiments　and　investigate　the　dynamic　soil　pressure　characteristics　under　different　factors.　The　test　and　numerical　results　showed　that　the　dynamic　responses　of　the　upper　tunnel　monitoring　points　are　stronger　than　the　lower　tunnel,　but　the　maximum　vertical　settlement　of　the　lower　tunnel　vault　is　bigger　and　prone　to　damage.　As　the　depth　increases,　the　stress　of　the　surrounding　rock　interlayer　at　each　monitoring　point　gradually　decreases.　In-depth,　the　surrounding　rock　stress　decreased　approximately　non-linearly　with　increasing　surrounding　rock　grade　and　surrounding　rock　interlayer　thickness.