| Slope instability is an important issue in hydraulic engineering.It has become a global geological hazard,considering the billions of dollars economic losses caused by it each year.Slope stability analysis and instability risk assessment are paid on more attention to recently.Slopes in hydraulic projects are generally natural slope,involving significant heterogeneity.Heterogeneity of the slope characters will affect the slope stability analysis and instability risk assessment using using the traditional methods.Unlike the conventional risk sources(e.g.construction methods,personnel quality,etc.),the heterogeneity and the spatial variability of parameters have not been paid enough attention in the analyses of the slope failure risk.In order to improve the accuracy of risk assessment of high slope in hydraulic projects,this paper carries out the study of heterogeneous slope stability,relying on the key project of Chongqing Municipal Science and Technology Commission of Science and Technology(cstc2015jcyj BX0039).And the main content of this research is as follows:1.Analysis method of the stability of the heterogeneous slope.In this paper,we analyze the sources of the uncertainties and spatial variability of parameters of slopes.And the approaches to generate the random parameter fields with the distribution function,the autocorrelation and cross correlation are also studied.A method to obtain the failure probability of the slopes is proposed on the basis of the Monte Carlo simulation.With a one-dimensional infinite long slope as an example,the influences of the randomness of the parameters on the statistical law of slope safety factor are explored.The results show that the probability of one-dimensional infinite slope instability is related to the variance,the mean value,the correlation scale,the cross-correlation coefficient of parameters and so on.The potential sliding surface of the heterogeneous slope is not necessarily the bedrock surface,and the frequency of the sliding surface appears to increase with the depth.2.Influence of spatial variability of parameters on slope instability.The principle of strength reduction of slope stability is expounded.Using the proposed random field generation method,the slope stability under different random parameter fields is analyzed.The relations between the statistical law and the correlation scale,the variance,the anisotropy of the parameters are revealed.And a risk assessment method of slope instability considering the probability of instability is proposed.The results show that the spatial variability of the parameters has remarkable influences on the slope safety factor and the position of the potential slip surfaces.And the higher the parameter autocorrelation is,the higher the probability of slope instability is.Under the same conditions,the risk of destabilization of soil slope is higher than that of a vertical slope.3.Study on the instability risk of a high rock slope in Chongqing.The stability of the high rock slope is studied by limit equilibrium method and strength reduction method under deterministic parameters.The safety factors under different working conditions are calculated and compared.The influences of the parameter measurement uncertainty and the parameter spatial variability on slope stability analysis are studied.And the risk of slope instability is evaluated based on the probability of instability.The results show that the parameter uncertainty will cause the slope safety factor dispersion and the changing of the location of the sliding surface.If the parameter heterogeneity is not accurately described,the slope stability analysis results are also imprecise,resulting in misjudge of the slope stability in analyses.Under the given spatial variation of the parameters,the risk of instability of the slope is relatively higher,on the basis of the assessing method mentioned above.The protection work is strongly recommended in the process of slope excavation,construction and later operation and management. |
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