The Study Of Slope Reliability Based On FLAC3D And Monte-Carlo

The slope reliability is an important issue of the Rock and Soil Mechanics Engineering. On the one hand, the slope stability factors are uncertain and the traditional safety factor cannot be very accurate to express the failure probability of the slope. Therefore, the reliability theory is introduced to slope stability analysis. The reliability expresses the stability of the slope by calculating the failure probability. On the other hand, rock and soil are complex mechanical medium and have their own constitutive characteristics. Moreover, because of the creep damage, the water content changes and the mechanical and chemical potential erosion or other reasons, the strength parameters and structural surface constitutive relation of geotechnical materials are gradually changed. The stability studies of slope should consider the time effect of stress-strain relation. The main purpose of this paper is to study the slope stability and reliability by considering the time effect.The main methods of the slope reliability are Monte-Carlo method, rosenblueth method, first-order second-moment method, stochastic finite method, the response surface method and the gradient optimization method, etc. Monte-Carlo method is a universal application and relatively precise of the three methods. Therefore, this paper intends to take the Monte-Carlo ideological into numerical calculation model and propose the reliability analysis method of slope which based on the FLAC3D and Monte-Carlo method. The main work can be summarized as follows:(1) This paper discusses the basic theory of geotechnical materials constitutive model and reliability calculations, and then statistical analysis the factors of slope destruction. The randomness of the internal friction and cohesion of rock and soils are mainly considered when establish the random model.(2) Then, this paper make a statistics of digital characteristics distribution of rock and soil material and determine that use Monte-Carlo random sampling for analysis which based on generate normally distributed.(3) At last, this paper proposes the calculation process of FLAC3D and Monte-Carlo method of slope stable reliability analysis and the programming of FLAC3D will also be prepared.(4) With the detailed survey information of Chongqing Daping landslide, this paper analyzed the stability and reliability of the Daping third landslide. During the analysis we assumed the cohesion and the angle of internal friction as random variable and the two parameters are independent. The paper uses the strain softening model to FLAC3D strength reduction method to get a series stability factor. And then, the paper received the frequency histogram of the uphill and downhill safety factor and finds the failure probability and reliability. At last, this paper compared the calculation results with the results of transfer" coefficient.The results show that, the stability of uphill and downhill of Daping third landslide are poor. The downhill is in a more dangerous state which because of the impact of ground water, and its reliability is only18%. Finally, the compared results show that the two methods are basically identical and they can authentication each other. The results also illustrates the method which proposed in the paper has a certain reliability. The median stability factor value which calculated by strength reduction method are smaller than the transfer coefficient method. The main reason is that FLAC3D do not need assume the transfer relationship between the bars and be able to take into account the deformation coordination between upper and lower soil so that it can be objectively reflects the slope real environment.