An　integrated　model　of　an　offshore　wind　turbine　(OWT)　which　incorporates　wind　turbine-water-pile-soil　interactions　and　cyclic/dynamic　behaviour　of　saturated　clays　with　pore　fluid　pressure　is　introduced　to　study　the　dynamic　behaviour　of　OWT　monopiles　in　clay.　Based　on　the　integrated　model,　the　influences　of　threedimensional　(3D)　seawater　modelling　and　operational　conditions　on　monopiles　are　investigated.　The　analysis　results　show　that　under　wind-wave　loads,　the　significant　accumulation　of　excess　pore　pressure　can　be　observed　in　the　seabed　soil,　and　use　of　the　effective　stress　method　involving　excess　pore　pressure　in　integrated　dynamic　analyses　of　OWTs　is　essential.　Compared　to　conventional　added　mass　methods,　the　consideration　of　the　3D　feature　of　the　seawater　leads　to　more　intense　dynamic　responses,　such　as　cumulative　displacement,　soil　damping　and　pore　pressure,　and　neglecting　the　3D　nature　of　seawater　is　non-conservative　for　the　design　of　OWT　monopile　foundations.　Furthermore,　the　value　of　the　soil　damping　is　affected　by　the　actual　effective　stress　state　of　soil　and　operational　conditions,　and　using　an　empirical　constant　to　determine　the　value　of　soil　damping　is　questionable　for　the　dynamic　analysis　of　OWTs.