Study On Slope Safety Assessment And Hazard Warning Along Highway In Mountainous Area

Along with the dramatic increase in infrastructural investments, the pace of highway construction has considerably speeded up in recent years, and the grade of highways has been also improved. In the meantime, slope stability has become a concern in many cases. During the construction process, originally stable soil slopes are destroyed or disturbed more or less, and become new man-made slopes. Hence slope safety assessment and hazard warning for the slopes have become an important subject.Supported by Department of Transportation of City of Chongqing, through Project CQJ20060101: Safety Assessment, Monitoring, and Hazard Forecasting and Prevention of Highway High-Cutting Slopes, this dissertation focuses on the safety assessment and hazard warning of slopes along mountainous highways. Main conclusions and achievements are outlined as follows:1.The failure mechanism of four types of highway slopes, i.e., homogeneous slope, bedding rock slope, anti-inclined rocky slope and wedge slope, have been analyzed, and verified with typical cases. Complex characteristics of slope hazard of mountainous highways have been studied in terms of existence and evolution.2.A holistic safety assessment index system for highway slopes comprised of 25 indexes, which are grouped into six factors (topography and landform, geologic condition, weather condition, soil properties, earthquake, and construction process) has been established, and a coupled weighting method for determining safety assessment indexes based on simple correlation, analytic hierarchy process, and expert opinions has been developed.A matter-element assessment model for the slope of mountainous highways has been developed, and applied for the holistic safety assessment of the k88+680 slope and the k90+380 slope of Wushan-Wuxi Highway, the k23+560 slope of Wushan-Fengjie Highway, and the k16+670 slope of Pengshui-Wuchuan Highway in Chongqing.3.In the case study of k87+560~740 of Wushan-Wuxi Highway, the cutting process was modeled with ANSYS for analyzing the local slope stability during cutting.A mathematic model for the local slope stability of mountainous highways has been developed, by coupling the unified strength theory and the Lode stress parameters. Slope data were pre-processed and analyzed. Studied slopes were modeled with finite-element software, and thus nodal parameters were obtained. Numerical results were post-processed and visualized with ArcGIS9.3. Thus, a safety map for the studied slopes was obtained.4.The spatial zoning indexes of slope hazard warning and a related warning classification system have been initially established based on the study region of Chongqing. Data collection approaches for the indexes and major warning zoning processes have been analyzed in detail. Spatial zoning studies of slope hazard warning were undertaken for the 2km buffering zone of main highways in Chongqing.5.Based on the three-stage slope deformation evolution rule, the evolution stage of the Gushuwu slope of Shanghai-Chengdu Highway was identified, using the tangential angle of the cumulative displacements for slope deformation.Grey theory and Markov model have been coupled for forecasting slope deformation during highway cutting; that is, the grey GM(1,1) model takes account of the gray features of slope deformation, and dynamic Markov process takes account of the randomness of slope deformation due to various influences, particularly cutting process. Case studies indicate that the coupled model provides precise forecasting results for slope deformation during cutting, and accurately predicts the magnitude of slope deformation. Based on the analysis of highway slope deformation under phased cutting, a creep-spline coupling model has been developed for forecasting deformations subjected to intermittent excavation.6.The development of the information system of safety assessment and hazard warning for the slope of mountainous highways has been analyzed, in terms of design objectives, design principles, integration, and operating environment. Also, main functions of three subsystems, i.e., holistic safety assessment, local safety zoning, and hazard warning, have been designed. The implementation of importance ranking, weighting, correction, and slope safety classification for the subsystem of holistic safety assessment has been discussed.