GAP　model　will　be　modified　and　programmed　by　FISH　language,　which　can　be　used　in　FLAC2D　programs.　The　modified　GAP　model　is　used　to　study　the　variation　of　surface　settlement　shape　with　depth,　the　variation　of　the　maximum　settlement　value　with　depth,　and　the　variation　of　settlement　gradient　with　depth.　The　results　show　that:　the　settlement　shape　is　narrow　and　deep　with　the　conditions　of　shallow　buried　depth　of　tunnel;　on　the　contrary,　the　settlement　shape　is　wide　and　shallow;　When　the　tunnel　depth　is　less　than　the　critical　value,　the　tunnel　depth　and　the　maximum　surface　settlement　is　approximately　linear;　when　the　tunnel　depth　is　greater　than　the　critical　value,　the　curve　of　maximum　surface　settlement　value　with　depth　becomes　flat　and　with　the　increase　of　the　tunnel,　the　surface　settlement　gradient　gradually　decreases　and　eventually　tends　to　zero.　It　is　more　reasonable　to　assess　the　influence　of　tunnel　excavation　near　adjacent　buildings,　using　the　maximum　surface　settlement　and　the　settlement　gradient　as　a　control　standard.