The mechanical strength and water conduction characteristic of rock mass near the surface are mainly controlled by joints and fractures. The ubiquitous joint mechanical model and saturated-unsaturated equivalent continuum media seepage model are coupled by joint connectivity rate to simulate the leading role of the joints. Based on FLAC3D

the mechanism of seepage-mechanics coupling，treatment of rainfall boundary condition and connectivity rate evolution are elaborated

as well as new multi-group ubiquitous joint model is developed. Through analysis of seepage and mechanics fields in a platform slope of Hainan iron ore under rainfall

it is shown that rock near the surface is saturated rapidly with the formation of transient saturated zone due to the rainfall. As the rain continues

the negative water pressure region has further shrunk while the transient saturated zone is just on the contrary. After the rain

the transient saturated zone begins to decrease due to rapid water pressure dissipation. The simulation also indicates that the layer is fractured and its connectivity rate is changed as well because of the seepage in rainfall process. Therefore

the coupled model above is reasonable to analyze the influence of slope stability under rainfall condition.