This　study　experimentally　analyzed　the　influence　of　shear　processes　on　nonlinear　flow　behavior　through　3D　rough-walled　rock　fractures.　A　high-precision　apparatus　was　developed　to　perform　stress-dependent　fluid　flow　tests　of　fractured　rocks.　Then,　water　flow　tests　on　rough-walled　fractures　with　different　mechanical　displacements　were　conducted.　At　each　shear　level,　the　hydraulic　pressure　ranged　from　0　to　0.6　MPa,　and　the　normal　load　varied　from　7　to　35　kN.　The　results　show　that　(i)　the　relationship　between　the　volumetric　flow　rate　and　hydraulic　gradient　of　rough-walled　fractures　can　be　well　fit　using　Forchheimer＇s　law.　Notably,　both　the　linear　and　nonlinear　coefficients　in　Forchheimer＇s　law　decrease　during　shearing;　(ii)　a　sixth-order　polynomial　function　is　used　to　evaluate　the　transmissivity　based　on　the　Reynolds　number　of　fractures　during　shearing.　The　transmissivity　exhibits　a　decreasing　trend　as　the　Reynolds　number　increases　and　an　increasing　trend　as　the　shear　displacement　increases;　(iii)　the　critical　hydraulic　gradient,　critical　Reynolds　number　and　equivalent　hydraulic　aperture　of　the　rock　fractures　all　increase　as　the　shear　displacement　increases.　When　the　shear　displacement　varies　from　0　to　15　mm,　the　critical　hydraulic　gradient　ranges　from　0.3　to　2.2　for　a　normal　load　of　7　kN　and　increases　to　1.8-8.6　for　a　normal　load　of　35　kN;　and　(iv)　the　Forchheimer　law　results　are　evaluated　by　plotting　the　normalized　transmissivity　of　the　fractures　during　shearing　against　the　Reynolds　number.　An　increase　in　the　normal　load　shifts　the　fitted　curves　downward.　Additionally,　the　Forchheimer　coefficient　beta　decreases　with　the　shear　displacement　but　increases　with　the　applied　normal　load.　(C)　2017　Elsevier　B.V.　All　rights　reserved.