Comprehensive Comparison And Analysis Of Green Support Scheme For Foundation Pit Engineering Of Railway Bridges In Northwest China

With the increasing function of railway bridge construction in the northwest region,the depth of the foundation pit of the bridge is continuously increasing,and the impact on society,economy and environment is also deepened.Although the foundation pit support is a temporary project,the buried member of the supporting member is destroyed.The original environment and the destruction of the natural soil environment have a negative impact on society,ecology and even the economy.There are many support schemes,and they are limited by the influence factors of the surrounding environment.The comparison of the foundation pit support scheme is a typical fuzzy multi-objective attribute decision-making problem.How to choose the appropriate green support scheme is especially important for decision-making.This paper firstly combs the domestic and international research results,analyzes the deficiency of traditional support and the difference with green support,combined with the unique geographical and geological environment in the northwest,based on the PSR framework model in the ecosystem,selects the pressure class and state.Three types of indicators,class and response,and construct a comparison analysis index system and mathematical model.Then use the triangular fuzzy number to calculate the index weight,which combines the interval number probability,gives the upper,middle and lower limits of the fuzzy interval,and reduces the omission of information in the analysis decision process.The FTOPSIS method is used to carry out comprehensive analysis and comparison of the schemes,calculate the relative approximation and rank the three alternative green support schemes.Considering the contingency of using the single comparison method to obtain the decision results,this paper uses the FTOPSIS expansion method A-FTOPSIS and F-FTOPSIS method to make the decision again,and gives the relative proximity to the confidence interval and the confidence interval of the relative proximity.The concept greatly reduces the loss of fuzzy decision information,reduces the randomness of decision results,and fully displays all calculation results,making the results of comparison decision more accurate and effective.Finally,three kinds of methods are used to compare and select the three foundation pit green support schemes of the Moguhe No.1 special bridge project.The order of the three schemes is calculated as follows: the assembled foundation pit steel support system> deep mixing Pile + composite soil nail wall support > Larsen steel sheet pile + cofferdam support,the best green support scheme is determined as the assembled foundation pit steel support system.In order to further study the accuracy of the comparison results,the sensitivity of each index is analyzed.The results show that F-FTOPSIS can more clearly reflect the decisionresults,and fully verify the validity of the method and the consistency of the conclusions.This paper studies the comprehensive comparison and selection of the green support scheme for the foundation pit of railway bridges in Northwest China,breaks through the research thinking of traditional foundation pit support,and provides ideas for the research of green support comprehensive comparison.