| On the foundation of the seepage problem finite element method formula, two-dimension finite element calculation program of steady and unsteady seepage problem has been worked out. Compared to various kinds of calculating seepage free surface methods, on this basis proposes one new calculating method of the seepage free surface -- variable seepage coefficient method. Using the method to calculate seepage free surface which only one gridding is needed, the position of free surface can be calculated precisely through program iteration totally. The two examples show that variable seepage coefficient of element method and unsteady seepage program arecorrect.The program is utilized to calculate soil rocks dam free surface position variation and pore-water pressure distribution condition with time when the up water level position changed. The changing rule of the seepage field under the different dam type, permeate coefficient and different rising or falling speed of the water level is explored. Pore-water pressure distribution calculated by the program is used to slope limited equilibrium analysis, is synthetically analyzed with the fluctuation of the upper reach's water level ofdam and core-wall dam upper or down are analyzed synthetically when the upper water level changed.An attempt on the development and improvement of calculation seepage free surface methods is presented. Through the elaborate design and comparatively furthering analysis of the numerical examples, the laws of the seepage field distribution and the slope failure mechanism due to these are furthered to be recognized when water level changed. All these have the theoretical meaning and applicable value, and also present useful reference to the slope stability analysis, slope disaster prediction and slope control etc. under unstable seepage.
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