(1. PLA University of Science and Technology，Nanjing，Jiangsu 210007，China；2. School of Earth Sciences and Engineering，Nanjing University，Nanjing，Jiangsu 210093，China)
Abstract：Three weak interlayers were found in the rock mass of Jiudingshan slope by outdoor investigation，which control the stability of the slope. The deformation characteristics of the slope rock mass are studied using numerical simulation. The results indicate that：(1) large relative slide will be induced by the direct excavation，and the maximum horizontal displacement，1.25 cm，happens on the slope surface where the weak interlayer P2 emerges；and (2) the relative deformation makes the strength of the weak interlayers reduce to be the residual one，which makes the slope more instable. The maximum shear stresses at the middle and front of the weak interlayers P1 and P2 are 239.0，172.4 kPa respectively. When the slope is strengthened by anchors，the axial force increases rapidly near the weak interlayers，which indicates that the anchors make the stability of the slope be improved. The stability coefficient of the slope after reinforcement calculated by strength reduction method is 1.65. It is shown that the numerical simulation can give the variation process of deformation and stress in the slope，and it is helpful for engineering optimization，informational design and construction.
