| As a dam-building country in the world,China ranks first in the world regardless of the scale and number of dams.Among more than 98,000 dams completed,more than 90%are earth-rock dams.According to statistics,in the dam accidents,the proportion of earth and rock dams is as high as 70.5%,and the flood and dam body instability of earth and rock dams are the two main causes of earth and rock dam accidents.Therefore,it is of great practical value to identify the earth-rock dam sliding rules in time,study the earth-rock dam slope instability,and then take corresponding measures to prevent the risk of earth-rock dams or reduce risk losses.For slope stability analysis,the accuracy of slope risk analysis results is affected by the probability distribution of the shear strength parameters of the soil.The shear strength parameters c and ? are important factors in slope stability analysis,and they are also sensitive random variables in slope risk analysis.At present,the analysis of the probability distribution characteristics of the shear strength parameters is mainly the fitting of the edge distribution of the shear strength parameters,and the uncertainty of the shear strength parameters has not sufficiently affected the slope stability analysis.Therefore,before studying the law of earth-rock dam sliding,the distribution of the shear strength index of the soil should be analyzed.In view of the superiority of the qualitative and quantitative bidirectional transformation cloud model in dealing with uncertainty,the following conclusions can be drawn:(1)Analyze the method and quantity of soil extraction,and synthesize the actual geological conditions of the soil extraction area,and use the grid sampling method in random sampling method to collect soil samples;perform indoor geotechnical tests on soil samples to control the soil samples.The maximum dry density and optimal moisture content are at the same level,which basically excludes the effects of poor gradation and non-uniformity on the shear strength parameters.(2)After the indoor direct shear test is completed,the distribution of the shear strength parameters of the soil is tested,and the hypothesis fitting test method is used to verify that the shear strength parameters obey both the normal distribution and the log-normal cloud distribution,and draw the distribution.Histogram;Based on the uncertainty cloud theory,using the indefinite reverse cloud algorithm to obtain the eigenvalues of the cloud,and draw the cloud diagram,which proves that the shear strength index of the soil obeys the logarithmic pan-normal cloud distribution.(3)Based on the measured data of an earth-rock dam,use the inverse cloud generator to obtain the characteristic digital expectations Ex,entropy En,and super-entropy He.Assuming that the shear strength index obeys the log-normal pan-normal cloud distribution,the forward cloud model is used to simulate random numbers,and the Monte Carlo method is used to calculate the probability of dam slope instability,and a risk analysis model based on cloud theory is established.Due to the complexity of the dam system,many input-output relationships can only be expressed as fuzzy relationships in reality recognition and from the data collection to the calculation results.There is a lot of ambiguity in the entire process.The objective reality of the system cannot be accurately described.There is a ambiguity of "one and the other." It cannot be described by 1-true or 0-false two-valued logic.Instead,multi-valued(or continuous)Value).The cloud theory is suitable for describing this kind of uncertainty in the system.Membership functions can be used to describe the transition problem of unclear boundaries and the uncertainty of complex systems affected by multiple factors.When conducting dam risk research,the randomness and ambiguity of each factor must be considered at the same time to carry out dam fuzzy risk analysis. |
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