Probabilistic study of slope stability under rainfall condition.

摘要

The primary objective of this research is to investigate slope stability under rainfall infiltration within a probabilistic framework. Using probabilistic approach, different types of uncertainties can be accounted for in a systematic and quantitative way. The stability of a slope can be represented by not only a safety factor but also a reliability index, which represents the probability of satisfactory performance of the slope. The information from various physical model tests can be utilized systematically to evaluate errors of prediction models by the Bayesian updating approach. In addition, reliability-based design can be conducted for the slopes.; Based on a nonlinear elastic coupled formulation for seepage and deformation of unsaturated soils, a coupled hydro-mechanical analysis program is developed. Numerical solutions to the coupled formulation are obtained using a finite element partial differential equation solver, FlexPDE. A finite element based slope stability program FESSA is also developed to calculate the safety factor of the slope based on stresses and pore-water pressure distributions obtained from the coupled numerical analysis. Coupled numerical modeling and slope stability analysis are conducted for two slopes. The first is the San Mau Ping slope, where a disastrous landslide occurred in 1976 after approximately 30 hours of heavy rainstorm. The second is the Kadoorie test slope where a field test was conducted to study the response of the instrumented nailed loose fill slope under artificial rainfall condition. Comparisons between the field measurements and the calculated results are made.; Essential soil properties that influence seepage and deformation in unsaturated soil slopes are identified.; A Bayesian framework is proposed to evaluate the model error of a prediction model using information from physical model tests.; As a special topic of slope stability under rainfall condition, the reliability of nailed soil slopes in Hong Kong is investigated. A spreadsheet for slope stability and reliability analysis of nailed slopes is programmed. Slope stability analysis and reliability analysis are conducted for three example nailed loose fill slopes. The effects of soil nails in loose fill are illustrated and discussed. Finally, the reliability-based design for nailed loose fill slopes is illustrated. (Abstract shortened by UMI.)