In　many　engineering　applications,　repeated　wetting　and　drying　is　one　of　the　most　destructive　processes　which　can　lead　to　continuous　damage　to　in　situ　rocks.　Worse　still,　the　situation　is　exacerbated　if　the　action　is　coupled　with　flowing　water　conditions.　In　this　work,　the　effects　of　wetting-drying　(W-D)　cycles　on　the　failure　characteristics　of　tunnels　excavated　in　the　gypsiferous　strata　were　investigated　by　using　the　particle　flow　code.　The　meso-mechanical　parameters　of　gypsiferous　rock　models　under　different　W-D　cycles　at　different　flow　rates　(0,　10,　and　20　l/h)　were　determined　by　the　trial-and-error　method.　A　two-dimensional　1/180　scale　model　of　the　tunnel　was　established　based　on　the　working　principle　of　centrifuge.　The　evolution　characteristics　of　force　chains　and　fractures　in　the　excavation　disturbance　zone　(EDZ)　under　different　conditions　of　W-D　cycles　and　flow　rates　were　analyzed.　Furthermore,　the　formation　mechanism　of　the　problems　in　the　South　Lvliang　Mountain　Tunnel　was　discussed,　and　some　prevention　measures　were　suggested.　The　results　showed　that　with　increasing　W-D　cycles　and　flow　rates,　the　fractures　and　disappearance　zones　of　force　chains　in　the　EDZ　gradually　increase,　while　the　influence　of　flow　rates　on　their　distribution　becomes　significant.　With　increasing　W-D　cycles　and　flow　rates,　under　the　unsupported　condition,　the　development　characteristics　of　growth　curves　of　fractures　will　gradually　transition　from　＂rapid　growth　to　stability＂　to　＂rapid　growth　to　slow　growth.＂　Under　the　support　condition,　the　development　characteristics　of　growth　curves　of　fractures　will　gradually　transition　from　＂rapid　growth　to　stability＂　to　＂rapid　growth　to　fluctuating　growth,　and　then　stability,＂　and　then　to　＂rapid　growth　to　slow　growth,　and　then　rapid　fluctuating　growth.＂　The　flow　rates　will　greatly　accelerate　the　deterioration　of　surrounding　rocks　caused　by　the　action　of　W-D　cycles,　thus　causing　the　lining　damage　in　a　shorter　time.