The problem of solving the seepage field with complicated boundaries frequently involves rainfall infiltration boundary as well as densely-distributed drainage hole boundary. This is in general an unsaturated seepage problem

and therefore

the traditional steady saturated drainage substructure model is not applicable any more. In this paper

according to the two classified drainage holes

typical subdividing modes for the two types of drainage holes are offered and a hydraulic model for unsaturated drainage substructure is presented correspondingly. Additionally

other boundaries like rainfall infiltration boundary which are not considered in traditional model are introduced

making the model more comprehensive and improved.