| The background of the dissertation was based on some research efforts on some typical slope disasters, such as research on a landslide reinforced by stability piles in Shang-san Highway, and research on K81 rock slope reinforced by pre-stressed cables in Jin-li-wen Highway, and research on rockfall disaster induced by irrational excavation in Wenzhou. By means of a series of research methods, like site geologic survey, field monitoring, indoor and outdoor testing and numerical analysis, the dissertation studied some aspects in the area of slope engineering disaster as follows:(1) Summarized the development mechanics of slope engineering disasters based on our group's former research achievements and literature survey results, analyzed the major influence factors of slope stability, discussed the slope collapsing and failure mechanics as well as mechanical principle, and classified the basic failure mode of slope disasters.(2) Studied the method of slope stability analysis based on finite element shear strength reduction method (SSR method). Dissertated a methodological system of modeling and parameter selection. Particularly discussed the failure criterion of SSR method. Then studied the calculation precision of SSR method affected by the change of various parameters. And compared the results calculated by method of SSR and method of limit equilibrium like Spencer method. Dissertated the advantage and characteristics of SSR method in slope stability analysis of Shang-san Highway No.6 landslide.(3) Studied the development rules of soil arching effects behind the stability piles. Revealed the rules of pile-soil interaction around piles. Analyzed the shape of the soil arch behind the piles and its major influence factors. An equation of the arch shape was derived by regression analysis based on numerical results. And according to the equation, the influence factors of soil arching effects as well as percent of residual load acting on soil between piles was discussed. As a result, a series of design proposal were presented in order to make use of soil arching effects.(4) Based on a case of crush rock slope reinforced by pre-stressed cables in Jin-li-wen Highway, the pre-stressed anchorage mechanism in crush rock slope were systematically analyzed by 3D FEM. First, according to the site tested relational curves of cable tension forces and rock deformation, the physical and mechanical properties of rock mass was evaluated using numerical back-analysis method. Then,an analytic mechanical model was developed. Combined with site tested data and laboratory research result, the stress dispersion manner of cable's pre-stress was analyzed, the distribution of slope stress and deformation varied with influence of rock mass properties, cable tension tonnage as well as different anchorage structures was discussed, the rule of slope stress and deformation response under pre-stressed anchorage forces was studied. Then the slope surface compression deformation and subsidiary stresses changes rule with different pre-stressed cables intervals as well as different frame beam depths were discussed. The long-term loss of cable's pre-stress and the optimum anchorage angle were also discussed at last.(5) Summarized the development mechanics of rockfall disaster. Based on an engineering case of rockfall in Wenzhou, the dissertation had picked out the major controlling factors of the trajectory and set up a series of calculation formulas on the view of the engineering utilities. Discussed the present main measures of rockfall prevention. According to site survey result and calculation conclusions and based on the site conditions, a comprehensive control idea of rockfall hazards prevention were presented.And the dissertation's main innovative results are:? Selection of failure criterion in SSR method was analyzed. The results showed that the failure criterion should be combined with proper iterative algorithms, strain mode assumption and plastic flow rule. When numerical calculation convergence criterion is employed, arc-length control iterative algorithms and small strain mode should be adopted. When slope surface displacement abruptly changing criterion is employed, large strain mode should be adopted in consideration of numerical convergence. Some calculation examples shows that SSR method can obtain almost the same results as Spencer method.(2) The method of slope stability using FEM was systematically dissertated. The core technology of method such as FE modeling and parameters selection was analyzed. Based on a typical landslide analysis in Shang-san Highway, the application of FEM used in slope analysis was fully discussed.(3) Analyzed the development principle of soil arching effects behind stability piles and pointed out the development of soil arch could be divided into three phases according to the p-S curve. And the stress distribution and deformation of the soil around the pile has different characters in different phases.? Shape equations of soil arch behind piles were derived by regression analysis of numerical results and based on these equations the mechanical reasons of arching effects affected by space between piles was an explained.(5) The anchorage mechanism of pre-stressed cables in crush rock slope was systematically discovered by the way of numerical simulation. The slope surface compression deformation and subsidiary stresses distribution were analyzed. And influence of changes with different pre-stressed cables intervals as well as different frame beam depths were also discussed. Some proposal was presented for designing purpose.(6) A series of calculation formula of rockfall trajectory were set up according to major controlling factors research on the view of engineering utilities. A comprehensive controlling idea of rockfall hazards was presented. The method shows great advantages in technology, economics and environmental protection compared with a single prevention measure. The ideals and the methods can be used to evaluate the rockfall trajectory and design the prevention structures of similar slope. |
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