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Research On Limit State Design Of Railway Embankment Slope Considering Variation Level Of Geotechnical Parameter

Posted on:2019-04-02Degree:MasterType:Thesis
Country:ChinaCandidate:A LiFull Text:PDF
GTID:2322330569488572Subject:Road and Railway Engineering
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To make up for the lack of consideration of the variability of geotechnical parameters by traditional safety factor methods,the reliability design method based on probability and statistics was introduced into the field of geotechnical engineering and became the future development direction of slope stability analysis.However,currently the research on slope stability design mainly focuses on Monte Carlo.Law and other reliability direct design method,although these methods can get the reliability of the engineering structure,but the calculation process is more complex and cumbersome,is not conducive to practical engineering applications.Based on the reliability theory,the partial state factor limit method retains the form of the allowable stress method design expression.The partial coefficient is used to correlate the result of the calculation with the reliability,accurately reflecting the safety of the structure,and the calculation is simple and convenient.Structural engineering is widely used.However,due to the large variability of natural geotechnical materials,the practical reliability index of the project is highly discretized.Using only one component coeff-icient does not ensure that the reliability of the geostructure reaches the target reliability,so it is necessary to apply The limit state design method for slope engineering was studied to promote the application and development of the partial-factor limit state method in slope engineering.The main research work and achievements of the paper are as follows:(1)Based on the variability of geotechnical materials and the results of scholars at home and abroad,the statistical analysis of the coefficient of variation of coefficient of soil shear strength ?c and ?? was performed.The variability of c and ? was subdivided into The three grades are small,medium,and large to facilitate the stability design that adapts to the actual operating conditions.The two equations of the limit state equation of the slopes g=Fs-1 and g=R-S are compared and analyzed.Compared with the former,the simplification of the calculation process is more conducive to practical engineering applications.Considering that the calculation model is a simple slope,the g=R-S form slope limit state equation based on the Swedish segmentation theory is selected.(2)The statistical analysis of the partial factors needs to consider as many as possible possible slope conditions.The simulation of the working conditions is achieved by different combinations of the basic parameters of the slope.The sensitivity analysis of slope stability reliability was carried out,and the influence characteristics of various geotechnical parameters and geometric parameters on the stability of slope stability were discussed.The significant influence factors were selected as the basic parameters of the working conditions;the basic parameters were assigned and the working conditions were simulated.Based on the existing regulations,the slope section and safety factor of the roadbed slope are used as control indexes to establish a combination of various strength parameters and geometric parameters of the slope model.Reliability is calculated to calibrate the reliability of the railway embankment slope.The research shows that the average value of soil strength parameters is the most important factor influencing the stability of slope.The coefficient of variation of soil strength parameters,slope height and slope rate are all significant influencing factors,and the soil bulk density has no significant effect on the stability of slope stability.Therefore,the average parameters of soil strength parameters and coefficient of variation,slope height,and slope rate are selected as the basic parameters;the reliability indexes calculated under various operating conditions are statistically analyzed,and the target reliability index of the railway slope embankment slope is 2.3.(3)The design value of variables is determined by checking the calculation point method,and the average value of the variables is taken as the standard value.The sub-item coefficients of the basic parameters of the slope are calculated under various combinations of conditions,and the soil strength parameters and the geometric parameters of the slope are analyzed.The impact characteristics showed that the soil strength parameter variability is the dominant factor affecting the partial factors,followed by the soil strength parameter average and the slope height,and the slope slope effect on the partial factors is weak.(4)In order to achieve a consistent reliability of slopes with different variability of soil strength parameters,a value-based principle that the partial factors should be adapted to the parameter variation levels is proposed,and statistics are made on the coefficient of the score items calculated under each operating condition.Analysis and calibration,given the soil strength parameters in the small,medium and large variability level of the corresponding resistance and load item partial coefficient(?RI,?R2;?S)recommended values were(0.75,0.95;1.02),(0.55,0.90;1.06),(0.40,0.80;1.10);compared with the values of the current specification,when the soil strength parameters are medium and large variation levels,the specification recommended for the cohesion The item R1 variability is seriously under-considered and basically only applies to the slope design with small variations in soil strength parameters.
Keywords/Search Tags:stability analysis of slope, variation level of parameter, partial factor, target reliability index, design point method, sensibility analysis
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