Abstract: Determining sliding surface and reliable shear strength parameters are crucial issues in evaluating slope stability. A new method based on numerical simulation technology is proposed to obtain reliable strength parameters without presuming the sliding surface. The relationship between heights and widths of thirty loess slopes at limit state in Lanzhou region were found to be linear,and the fitting degree was high. According to the obtained regression equation,FLAC was applied to establish the slope model, and strength reduction method was used to inverse the strength parameters of slope at limit state. Furthermore, the parameter inversion curves of four adjacent high slopes were drawn in the unified coordinate system, and the comprehensive strength parameters of the segment were acquired. The inversion results show that with the increase of slope height,the cohesive force of loess increases gradually but internal friction angle decreases. According to the calculation results,the comprehensive inversion curves of strength parameters of slope with heights from 60 m to 120 m are drawn. The method could directly evaluate the stability of high loess slope,improve the working efficiency,and also provides reliable data to support the geometry design of high loess slope.

Key words: high loess slope, FLAC, strength reduction method, parameters inversion, safety factor, Lanzhou region