Study On Selection And Optimization Of Ruling Grade In Capacity Expansion And Reconstruction Project Of Existing Railway Based On Multi-objective Decision Theory

In recent years,with the changes in the focus of China ’s railway development in the future,the construction investment for the expansion and reconstruction of existing railway lines is gradually increasing.At the same time,the passenger and freight volume of China’s railways is also increasing rapidly following the social and economic development.However,many existing railways have been built earlier,and its technical standards and transportation capacity can no longer satisfy the demand of railway development.Therefore,it is necessary to expand the existing railway’s capacity.However,the main technical standards of the existing line are relatively low,so it is unavoidable to take into account the problems such as excessively large ruling grade of the existing line profile.In the reconstruction design of existing railway lines,ruling grade is a major technical standard for railways that affects the overall situation.Whether the value is reasonable or not has a very important significance for saving railway construction investment,improving transportation capacity,and reducing operational risks.Therefore,in this paper,when studying the problem of ruling grade decision for the existing railway capacity expansion and reconstruction project.This paper proposes the use of multiobjective decision theory to implement the auxiliary decision-making.Through the optimization and combination of different mathematical models,the ruling grade comparison and selection’s matrix of the rebuilt railway based on the multi-objective decision theory is established,and the model is uesed in the actual case of the project.Firstly,by analyzing the necessity and importance of capacity expansion and reconstruction of the existing railway in China,this paper summarizes the technical characteristics and design steps of such projects,generalize the commonly used transmission capacity strengthening methods and selection principles,refine the connotation and general principles of the reconstruction design of the existing railway,and research on decision-making issues of major technical standards.Then,by analyzing the importance of the ruling grade value in the existing railway reconstruction design,and discussing the definition and design principles of the ruling grade,considering the factors influencing the decision-making of ruling grade from five aspects of:engineering conditions,engineering economy,engineering risk,road network coordination,and transportation organization,and then the analytic hierarchy process(AHP)is used to establish the ruling grade evaluation index system based on the existing railway reconstruction design.Secondly,by summing up the advantages,the disadvantages and the scope of application of common indicator weight determination methods,the weight of evaluation indicators is calculated by using the association of objective and subjective weight method based on the entropy weight method and weighted least-square method.By analyzing and comparing a variety of multi-objective decision-making evaluation methods,the optimization research is selected on the basis of the traditional mathematical model.This paper constructs two kinds of decision-making models for the ruling grade of the rebuilt railway based on grey-fuzzy comprehensive appraisal and based on the TOPSIS and grey correlation analysis.Finally,a multi-objective decision optimization model based on the ruling grade of the rebuilt railway is used to calculate the existing Haicheng to Xiuyan railway.Through comparing and analyzing several ruling grade route schemes,the final recommended scheme is obtained,which not only verifies the applicability of the decision-making theory and improves the scientificity of the decision-making of the route design scheme,but also provides a reasonable and feasible solution for similar decision-making problems in the future.