Study On Slope Stability Analysis Based On Interval Displacement Back Analysis Method

The accuracy of the numerical calculation results of geotechnical engineering depends on the selection of the constitutive model and the input parameters.At present,various geotechnical constitutive models have been established,including those with clear physical meaning,rigorous mathematical logic,and reasonable test verification.Various uncertainties in geotechnical engineering problems lead to a certain difference between the deformation characteristics of those constitutive models and the relection in actual engineerings.Although the geotechnical parameters that are relatively in line with the actual engineering can be obtained through the displacement back analysis method,which depends on the accuracy of the obtained monitoring displacement itself,and the actual monitoring is inevitably affected by factors of the geotechnical media itself,environment,the man-made and measuring instruments,which caused some inevitable errors in the actual application of the displacement back analysis method based on the traditional "point" deformation monitoring information.Traditional solutions to uncertain problems often require a lot of known information,while the interval analysis method requires less known information(such as the upper and lower bounds of monitoring displacement errors)to comprehensively consider the overall uncertainty in geotechnical engineering.Finally,the result of the inversion parameter is represented by an interval set containing the "true value" parameter.In view of the above-mentioned problems,this article introduces the interval analysis method on the basis of the displacement back analysis method to form an uncertain inversion method,and realizes it by programming in Matlab.Finally,through a landslide example,a preliminary construction of the slope "interval back analysis + stability forward analysis".The specific research work and results of this article are as follows:(1)Analysis and research of errors in deformation monitoring data.The influence of monitoring data error on slope engineering and its transmission process are analyzed through two aspects of stability forward analysis and displacement back analysis;the interval value method of deformation monitoring data is summarized on the basis of previous results and the calculation method of measurement uncertainty in modern error,the interval value method of deformation monitoring datas is summarized.(2)The objective function and optimization algorithm improvement of interval displacement back analysis method.The macroscopic mathematical model formula of the interval displacement back analysis method is given;the ranking interval numbers of order relation is introduced based on the "apperoximation" principle of traditional least squares,while referring to ideas and formula expressions of ranking interval numbers of possibility degree,the target function suitable for interval displacement back analysis method is proposed——an improved objective function based on the ranking interval numbers of order relation;According to the characteristics of the program interval displacement back analysis compiled in this paper,an improved optimization algorithm is proposed—an improved optimization algorithm based on Global Search-particleswarm.(3)Programming of interval displacement back analysis method and verification of calculation examples.Using Matlab as the carrier program,using the INTLAB toolbox to realize interval logic calculations,and using FEATool Multiphysics as the FEA calculation module,the program of interval displacement back analysis is compiled.The program is verified by a slope calculation example.The results demonstrate that the differences of inversion results are all within 3.5%,and as the errors of monitoring data increases,the accuracy of interval back analysis decreases,and the interval range of the back analysis parameters increases.In actual engineering,the accuracy of interval back analysis can be improved by improving the monitoring accuracy to obtain the solution of interval parameter of smaller and closer to the "true value".(4)Example application of landslide engineering.Through the design of orthogonal test obtained the interval stability coefficients under different comprehensive errors: the interval stability coefficients of landslide of 0.5 mm and 1.0 mm were [1.023,1.079] and[1.019,1.080] respectively.The results demonstrate that the landslide was basically in an under-stable state,and the larger the error,the range of final stability coefficient increases.In actual engineering,the accuracy of the stability coefficient can be further improved by improving the accuracy of the monitoring instrument;the midpoint value of the interval parameter is taken as an example to analyze the whole precess of instability damage of landslide under strength reduction FEM,which are three stages of slow growth of displacement-plastic zone beginning to develop,rapid growth of displacement-rapid development of plastic zone and dramatic growth of displacement-overall penetration of plastic zone.Finally,the middle and rear edges of the landslide become unstable and the landslide is destroyed as a whole.Through the landslide example,the interval displacement back analysis-stability forward analysis process was completed,which proved the rationality of the system of interval back analysis and stability forward analysis of slope designed in this paper,and also confirmed that the transfer process of errors monitoring displacement.The final interval stability coefficient obtained by comparison with the results of the existing literature shows that the significance of the interval value is not only the result of the initial error transfer,but also can include stability analysis results of different working conditions.interval analysis presents these as an interval value.