Abstract: In order to study the influence of the rise and fall of the water table on the permeability coefficients of the water-filled goaf， the equivalent permeability coefficients in three main permeability directions with strain as parameters were derived according to the cubic law. FISH function was used to improve the unsaturated seepage calculation function of FLAC^3D based on the fluid-solid coupling calculation model， and the unsaturated element of the equivalent continuous medium fluid-solid coupling model of mining rock mass was modified to realize the simulation calculation of the seepage field and stress field of water-filled goaf. The influence of the seepage field on the stress field was reflected by the absolute value of the difference between principal permeability coefficient ratio and 1. By comparing the calculation results of pillar central unit before and after model modification， it could be seen that: the value increases with the rise of the water table. The effect of seepage field on stress field before model modification is greater than that after model modification. After model modification， the maximum and minimum principal strain curves show an inflection point when the saturation is 1. Since the parameters of the seepage model before modification are the same as those of saturated seepage， it can be verified that the modified model is more consistent with the unsaturated seepage theory. Finally， by comparing the data of the groundwater seepage flow in actual working conditions， the modified model is verified to be more consistent with the reality.

Key words: water-filled goaf; fluid-solid coupling; permeability coefficient; seepage model; FLAC^3D