Abstract: The Xiangxi Highway Bridge in the Three Gorges Reservoir Area is faced with prominent engineering geological problems as f1 and f2 faults and multiple free faces developed in the high bedding slope. On the basis of survey data and field investigation, we analyzed the geological background, and finely evaluated the parameters of dominant structural planes of the slope via site mechanical test. Moreover, we calculated the safety factor of the slope in different structural planes in different layers and slip surfaces with different lengths via the Sarma method. We further established the relations of support force and average thickness of sliding body against safety factor. Results demonstrated that for bedding slope with structural plane penetrating through to ground surface, the safety factor of sliding body on the structural plane is in a negative correlation with the average thickness of the sliding body, and in a weak correlation with the length of the sliding surface. The slope body can be divided into three sections according to the terrain: the locking section at slope foot, the main sliding section, and the pulling section at slope top. The sliding body on the f1 fault has insufficient safety reserve because of large thickness of rock layer and low strength of the sliding surface: the shear-off peak friction angle is 27.0°, the cohesive force is 0.07 MPa, the residual friction angle is 25.2°, and the residual cohesion is 0.05 MPa. An additional support force of 4 283 kN/m or unloading 32.6% of the slope volume is needed to meet the lower limit of stability standard. Due to huge work quantity, we recommend anti-slide pile design in combination with engineering excavation.

Key words: high bedding slope, fault, structural plane, direct shear test, stability evaluation, safety factor