| The evaluation and prediction of landslide stability is the core content and precondition of landslide prevention and control, also a hot and difficult problem in the field of landslide research. Since the Saito model has been proposed, many scholars have made fruitful achievements and considerable progress on evaluation and prediction of landslide stability. However, from the perspective of the existing landslide prediction methods and models, it should be believed that whether they are the statistical methods based on the empirical or the mechanics analysis methods based limit equilibrium, they all have some disadvantages and limitations. The debris landslide is a kind of complex nonlinear system, the deformation evolution rule is complex, it is very difficult to achieve the purpose of prediction and control effectively by using of the traditional evaluation and prediction method of landslide. So it is urgent to put forward and establish a evaluation and prediction method of landside stability which will be more suitable for current knowledge level and the application practice to meet the needs of landslide prevention and remediation.Aimed at the above problems, on basis of analyzing the basic characteristics of the debris landslide and existing evaluation and prediction method of landslide stability, starting with the complexity and systemic of the landslide, with water as the power factor of the debris landslide deformation and failure, the landslide stability evaluation parameters and prediction method of Unload-Load Response Ratio based on coupling of system dynamics and displacement was put forward in this paper. On basis of systematically analyzing the connotation of Unload-Load Response Ratio and its feasibility for landslide stability evaluation and prediction, Unload-Load Response Ratio model based on changes of hydrodynamic was proposed. Through the numerical simulation and analysis of landslide unload-load response of reservoir water, rainfall and groundwater, corresponding Unload-Load Response Ratio numerical analysis model was established, the Unload-Load Response Ratio and stability coefficient of landslide at different stages were identified. It was found that the change tendency of Unload-Load Response Ratio was consistent with the stability coefficient of landslide, which showed that the Unload-load response ratio and the stability coefficient were the same, which could reflect the stability of the landslide effectively. On this basis, the thesis utilized fundamental theory of damage mechanics to establish the quantitative relationship of Unload-Load Response Ratio and slope safety factor, determined the stability planning standards based on Unload-Load Response Ratio combined with the engineering survey specifications, and put forward that the Unload-Load Response Ratio is a new kind of safety factor based on damage mechanics and reliability. And through the analysis of the evolution law of the stability of Xintan landslide, it was found that the Unload-Load Response Ratio calculated by using actual monitoring data was just as consistent in the actual landslide stability, the results indicated that using the Unload-Load Response Ratio to evaluate and predict landslide stability was effective and feasible to some extent. The main conclusions and results of this paper are as follows:(1) Through the Systematic research to the debris landslide formation geological conditions, the basic composition, the dynamic deformation mechanism and deformation characteristics, etc., often think of debris landside development at the water near the leading edge of the ramp or more open slopes, accumulated and formed by the secondary residues, colluvial sediments, slope deposits and alluvial deposits. The special material composition and structure of the slope determines the total displacement of this kind of landslide should be a comprehensive reflection of the whole deformation, water becomes the main reason for its failure and deformation.(2) The article proved and determines that complexity theory gave prediction and evaluation of landslide stability apocalypse of methodology. Landslide is complex, the complexity problems of the landslide need to be solved by complexity theory. "Old three" represented by system theory, cybernetics and information theory, and the "new three" represented by dissipative structure theory, synergetics and catastrophe theory, provided the new methodology for the exploring of landslide stability evaluation and prediction methods. Based on the basic theory of complexity theory, organic integrating systems theory and nonlinear dynamic theory, the mechanism and law of the nature and evolution of the complex open system were analyzed to explore the evaluation and prediction method of landslide stability.(3) The paper put forward the Unload-Loading Response Ratio prediction parameters and evaluation methods which was suitable for debris landside stability. Starting from the black-box method, to apply catastrophe theory and dissipative structure theory to analyze the changing process of the landslide structure during its material and energy exchange with the outside environment, with the research method that combing the dissipative structure theory and damage mechanics method, to define damage variable from the perspective of the relationship between dissipation energy and constitutive energy in the process of energy dissipation, the damage variable was converted to a method of representing relationship of contrast between the value of stress and strain variation, to describe and express the damage extent of landslide body and Unload-Load response ratio, which is scientific, reasonable and available for landslide stability evaluation and prediction.(4) The connotation of Unload-Load response ratio was described, the water dynamic action on debris landside was discussed, and Unload-Load response ratio evaluation model based on hydrodynamic(rainfall, reservoir water and ground water) was established, and the preliminary criterion for the analysis of landslide stability loss was proposed: when Y′< Yï¿ -s and Y′â†'0, the slope will lose stability. The accuracy and feasibility of the Unload-Load response ratio for landslide stability evaluation were verified by an example.(5) Bank wading landslide classification was proposed based on k/v ratio. Using Slope permeability coefficient k and reservoir water fluctuation rate v, the two most critical and contradictory elements which influence the change of seepage field, the bank wading landslide was divided into two categories of k/v>1 and k/v<1. This is a kind of dynamic classification method with the change of water environment conditions, in order to meet the need for evaluation and prediction of landslide stability based on mechanical mechanism.(6) The paper analyzed the reservoir water, rainfall, groundwater changes on the accumulation effect of the unload-Load response of the debris landslide through numerical simulation, and calculated the respective Unload-Loading Response Ratio and the stability coefficient of landslide, the results showed that the change trend and rule of time series of Unload-Load Response Ratio was consistent with stability coefficient’s, when the Unload-Load Response Ratio decreased, the stability coefficient of the slope was in reduced state, and when Unload-Load response ratio increased, the stability coefficient of the slope would increase also. It showed that the Unload-Load response ratio could better reflect the stability of the slope, which was proved to be effective and feasible to evaluate and predict the stability of the slope based on the mechanism.(7) The quantitative relationship between the Unload-Load Response Ratio and the safety factor was established. Based on the perspective of damage mechanics, the inoculation process of landslide was considered as the damage evolution process of the landslide, and the function relation between the Unload-Load response ratio and the damage variable was derived: Y -=Dï¿ 1. It showed the Unload-Load Response Ratio could quantitatively reflect the damage evolution process of landslide slope at the macro. The damage variable D described the degree of damage and deformation, and the variable Y ï¿ reflected the rest stability of the slope. By defining landslide stability factor as the ratio of limit damage and current damage, the quantitative relationship between Unload-Load Response Ratio and stability coefficient was establishing:Y’=1-1/F.(8) Combing the engineering survey of landslide prevention and control, design specification and related research literature, the state of landslide stability classification scheme based on Unload-Load Response Ratio was proposed to realize the landslide stability evaluation and prediction. When the Y′=0, the landslide stability lost; when 0<Y′<0.05, landslide is unstable or marginally stable; when 0.05≤Y′<0.13, landslide is basically stable or temporarily stable; when Y′≥0.13, the landslide is in steady state. Therefore, the Unload-Load response ratio can not only be used as a criterion for landslide stability, but also can be used for quantitative accurate evaluation of landslide stability.Through the calculation of Unload-Load Response Ratio of Xintan landslide, it was found that numerical value obtained, its corresponding landslide stable state and actual changes of landslide situation were in agreement, which is to say using Unload-Load Response Ratio in the design of prevention and treatment prevention and cure project is of great theoretical significance and practical application value.The research shows that, Unload-Load Response Ratio as a method of displacement dynamics, takes into account both the landslide system external characteristics change-Unload-Load response(displacement, displacement velocity, displacement acceleration, etc.) and the Unload-Load dynamic factors that causing these response(rainfall, reservoir water, groundwater changes), and embodies the landslide deformation mechanism and deformation process from the view of causality and input – output. It can not only be used as a criterion to predict landslide instability, but also can quantitatively evaluate landslide stability, which opens up a new idea and method for the stability evaluation and prediction of the landslide. |
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