Abstract: Both movement characteristics of the roof strata belonging to underground mining and slope stability of open pit when the remaining coal resources of open pit slope are recovered by underground mining in Antaibao open pit are studied by numerical simulation software FLAC3D.The results show that the evolution law of the compressive stress and compressive strain of open pit slope are shown by nonlinear decreasing trend as the different distance away from the ground stop line of open pit.Stress concentration of the roof is shown by asymmetric and compressive strain of the roof is reduced by nonlinear trend as the continuous underground mining.Tensile stress zone obviously biased the free end direction of open pit slope will be produced.Both the extrusion and movement caused by overlying rock and soil of open pit slope and the deterioration effect on the bottom rock mass of open pit slope caused by mining are the key factors leading to the open pit slope slip.There is a theoretical size for underground mining which can maintain the open pit slope safe and make the coal be recovered as much as possible.

Key words: Open pit, Underground mining, Stability, Numerical simulation