Landslide Progressive Failure Reliability Analysis Based On Fuzzy Stochastic Theory

The landslide is not only a natural disaster, but also a kind of serious engineering geological disaster, its occurrence and development is limited to the geological condition and natural forces, at the same time,which is also influenced by the human activity. The large landslides,which are in large scale, and the mechanism of them are complicated, the large potential energy is formed when they separate themselves from the parent rocks, they often cause a series of complex geological disasters, produce the chain reaction, and the typical disasters which are included of collapse, slide and debris flow. So, the landslide disaster seriously affected the people’s life and the security of property, they bring heavy casualties and losses to the whole socity. Therefore, the landslide stability and reliability analysis of the landslide engineering is all, and must be a key problems in the geotechnical engineering.In the field of the landslide stability reliability analysis, there are several severe problems:(1) The landslide stability analysis methods (such as single value stability coefficient method, traditional reliability analysis), which are all based on the traditional limit equilibrium theory, in the calculation of the landslide stability, the emphasis to the landslide stability are the single value solution of the whole index, the commonly used index to evaluate the landslide stability,such as overall stability coefficient Fs, the whole probability Pf and overall reliability indexes landslide β, etc. In the solving process of these indicators, we also assumed that sliding surface damage occurred a continuous whole sliding, the local index and the overall stability are the same index, they are not changing along the slide surface, this kind of thought, in practice, separates the internal evolution rule,which includes the landslide’s breed, deformation and failure,this is to say, the progressive damage evolution model in the landslide.(2) The traditional method of landslide to evaluate the stability of landslide, ignoring the fuzziness of landslide system, always based on the simplified calculation model subjectively, in creating a stable function between the reliability, function involves the stability up only the main controlling parameter, through calculation stability coefficient functions, when the function is0obtained corresponding numerical solution, use them to the landslide stability evaluation, this kind of practice, obviously is not proper, its evaluation results human factors is bigger, different people the results of the evaluation of the difference is very big, so the use of these accurate calculation method usually is not appropriate. Further research proof:fuzziness embodies the uncertainty than its randomness, more deeply, more of general significance.(3) Based on binary logic reliability concept based, it reflects people’s precise thinking mode, the fuzzy complex system reliability problems, simply be seen as the accurate mathematical problems and can’t truly reflect the objective reality, especially in geotechnical engineering, not all the uncertainty are random, based on cognitive incomplete information cause uncertainty cannot use probability theory to deal with. Accuracy and complexity mutual g principle indicated that, with the complexity of the landslide system of the constantly increasing, the people to make the stability of accurate and meaningful ability also reduced, until a certain threshold tends to, once more than the value, we make precise and meaningful judgment present a large degree of reactive characteristics. So, for such a complex system like the landslide, using the pure reliability theory to evaluate its stability is not enough, it is necessary to develop a method which is considered the random theory and also the fuzzy evaluation, this is the fuzzy reliability analysis method.In view of the problems mentioned above, this paper studies the progressive damage landslide form time and space development characteristics, using the fuzzy random theory which is different from the theory of reliability, taking the Baihe landslide, which is located at province song county, as an example, through establishing the surface crack development deformation characteristic of landslide,researching the partition deformation characteristics of Baihe landslide, judging its progressive damage model; analyzing the basic features of Baihe landslide, the characteristics slide soil and the progressive damage influence factors of the landslide, to illustrate the mechanism of progressive damage model; using random fuzzy processing method to determine--calculation model of fuzzy random variable, Based on the spatial variation in geotechnical engineering, consider the correlation of parameters to the fuzzy random variables as basic variable establish landslide progressive damage of fuzzy limit state equation; Through membership function of geotechnical engineering selection principle of different types, the application of the membership function is discussed, the selection of accord with the membership functions of the landslide deformation characteristics of progressive damage limit state equations are fuzzed, establish a2d progressive damage fuzzy random reliability model to analysis the landslide; On the basis of these, researching the occurance and extend of the local damage to progressive process of the landslide; by means of numerical simulation method, combined with the discrete particle flow code software to verify the rationality of fuzzy progressive stochastic reliability analysis, recreating the progressive damage process of Baihe landslide. Through a series of analysis mentioned above, the conclusion that:(1) Based on force characteristic and the progressive damage mode analysis of the landslide, the progressive damage model is divided into three typical mode:this is,the progressive going on type landslide, the progressive incremental traction type landslide, the progressive translation type landslide. Combined with the actual geological characteristics of the landslide area, in order to make a reasonable and reliable recognition to landslide progressive damage model quickly and easily, on the basis of previous studies, from the crack types, the stress of the crack surface features, summarizing the progressive damage surface crack development characteristics of two kinds of landslide deformation. Based on these, according to the geological background of the landslide and its stability influence factors, this paper analyzes the basic characteristics of Baihe landslide, from the investigation results of the earth’s surface crack development situation and progressive damage time evolution and space evolution rule, and also taking the fracture analysis of characteristics as foothold in each stage of the development, analysing the progressive going-on damage mechanism of Baihe landslide.(2) Combined the reliability. theory with the fuzzy mathematics, and researching combining site of them, in order to establish a unification reliability analysis method with stochastic theory and fuzzy theory. The description of geotechnical fuzziness when using the fuzzy mathematical, one of the core questions is the determination of subordinate function. By the analysis, this paper discusses the form membership functions when the fuzzy stochastic theory is applied in landslide engineering, the of basic construction principle of the membership functions, the instructions of different membership functions, and also the membership functions to landslide stability factor and engineering geotechnical parameter (mean and variance and covariance) is given in this paper.(3) To the limitation of the reliability analysis of landslide,such a complex system, using the pure reliability theory to evaluate its stability is far enough, we should carry out the evaluation method which not only considering the randomness, but also the fuzziness, this is the fuzzy reliability analysis method. Discussing the fuzzy factors in mechanics parameters of rock soil and limit state equation in the reliability analysis of the landslide, and putting forward geotechnical mechanical parameters and limit state equation of the basic means the fuzziness processing respectively. In landslide engineering,the explicit function and implicit function of landslide stability are researched, some common fuzzy reliability calculation method are introduced in this paper, some new ways to resolve the analysis the reliability of landslide are proposed based on implicit functions.(4) Considering the natural conditions, the pore water pressure condition and rainfall condition to landslide, different function expression of calculation methods to the safety allowance are deduced. According to a train of thought to the local damage fuzzy probability calculation and extended fuzzy probability calculation and damage progressive damage fuzzy probability calculation,the progressive damage fuzzy reliability analysis of Baihe landslide is analyzed. From the damage spread matrix in progressive failure of landslide, we can Draw The Following Conclusions:①The deformation of landslide begins in the back margins and forward after the failure mode of transmission development;②When the slice1is damaged, the gradual damage is probability transferring to its neighboring regions, the failure probability of landslide is even more likely. Overall, it seems that, spread probability from slice16to slice20, the failure probability of them are more likely than other slices, this shows that, the most dangerous part of the landslide located at16to20slices, therefore, the anti-sliding support structure should installed here in first consideration.③In different rainfall condition, the probability between same slices, with the increase of rainfall, the spread probability is increasing, so the possibility of damage are becoming more and more.④With the increase of rainfall time and precipitation, the one-time progressive scale of the destruction is the largest, but the transfer path of progressive damage are the same. The transfer path the of largest damage is:1-2-3-6-7-8to9-11-13-14-15-06) and (17)-(18)-(19)-(20)-21-24; Once the size of the progressive damage were94.3314m,114.6842m,131.6087m,149.2111m and153.6924m. respectively.(5) From incremental landslide deformation evolution characteristics, in view of the earth-rock aggregate landslide, the particle flow PFC program, emersion the Baihe landslide and the whole process of development and destruction. Numerical simulation results and simulation of random fuzzy reliability analysis by each other, and concludes that the progressive damage type landslide Baihe goes on the mechanical process.The above research results and conclusions, which provides some new ideas and methods to the landslide risk evaluation theory. Through the reasonable grasp of landslide deformation, it not only including its occurrence, development to the whole process of destruction,, it not only has very important practical significance to the prevention and mitigation landslide disaster of the landslide disaster, but also provides the theoretic basis and the technical support to the landslide forecasting and predicting.