Study On Expressway Asphalt Pavement Technical Conditions Analysis And Maintenance Decision Method For Cold And Arid Areas In Northwest China

With the rapid development of expressway in the cold and arid areas in northwest China,the expressway network system has been basically formed.However,due to the continuous growth of expressway mileage and traffic flow,most of the expressways have entered into the peak period of maintenance.Meanwhile,affected by the unique geographical location and high-cold climate,plateau permafrost,strong wind and drought,as well as the severe and diverse climatic conditions in the cold and arid areas in northwest China,the asphalt pavement diseases of expressway are progressively increasing and the causes are even more complicated.Using the data mining technology and intelligent algorithm,combined with the history of expressway asphalt pavement maintenance,the thorough analysis and research of asphalt pavement performance decay mechanism is performed,the technical condition evaluation and prediction model of asphalt pavement is studied and formulated,and an intelligent decision system of pavement maintenance is also built combined with maintenance funds and maintenance planning objectives.The present study not only provides important theoretical guidance to further improve the cold drought northwest science and timeliness of the expressway asphalt pavement maintenance decision-making,but also provides significant theoretical and technical support for China’s expressway asphalt pavement maintenance management.Based on the research of available literatures,and taking the maintenance decision of expressway asphalt pavement as the main line,the present thesis systematically studied the pavement maintenance decision and optimization of expressway asphalt pavement in northwest alpine region when investigating the problems of technical condition evaluation,performance prediction and pavement technical condition evaluation,pavement performance decay prediction,maintenance section determination and measure selection,maintenance cost allocation and optimization method of maintenance decision,which is conducted by using rough set,network analysis,interval number,fuzzy analysis,multidimensional connection coefficient and the other theories and quantitative and qualitative methods.(1)Through the systematic analysis of the connotation of highway asphalt pavement technical condition and the development course of its evaluation process,a multivariate complex system based on pavement technical condition is established,with emphasis on the relationship among the structural performance,functional performance,rutting performance,safety performance and structural bearing capacity of expressway asphalt pavement.And combining with the influence of the climate around,traffic flow,road age,construction and operation management and other factors on the technical status of highway pavement,an in-depth analysis is made and the types and expressive characteristics of asphalt pavement damage are also systematically summarized.Through the in-depth analysis of the general evaluation index system of asphalt pavement performance,the comprehensive evaluation index system of highway asphalt pavement technical condition is studied and established.(2)The thesis is based on the systematic and in-depth analysis of the generation mechanism and main types of highway asphalt pavement diseases in the cold and arid areas in northwest China,and combining with the fact that the fixed index weight in the traditional evaluation method is insufficient to reflect the actual road condition performance.The rough set knowledge granularity theory and network analysis are used to proceed from subjective and objective aspects.Based on the rough set knowledge granularity theory and ANP,a comprehensive evaluation index weight calibration method for expressway asphalt pavement is constructed.Meanwhile,combined with interval numbers theory,fuzzy evaluation method and incomplete information system based on rough set,the technical condition evaluation model of expressway asphalt pavement is established.Taking the highway under the jurisdiction of Gansu Province as the main research object,the feasibility and practicability of the model and method are further verified through the analysis of examples.(3)Through the prediction of influencing factors of asphalt pavement technical condition as well as the systematic summary and analysis of the traditional prediction methods,the technical condition prediction model of expressway asphalt pavement based on IFA-SVM is constructed associated with support vector machine and improved firefly algorithm.Field search and variable step strategy are introduced to overcome the random movement of fireflies with the increase of iteration times and to provide guidelines of the optimization selection of support vector machine model parameters.Then the corresponding performance index is selected to predict the technical condition of expressway asphalt pavement effectively.The validity of the model is verified and analyzed by examples.(4)Based on the analysis of the maintenance objectives of asphalt pavement of expressway,the main measurements of pavement maintenance and the corresponding technical schemes are combed further.According to the pavement technical condition and disease characteristics of expressway in the cold and arid areas in northwest China,the decision standard of pavement maintenance is established.The maintenance decision model which integrates the technical condition,road age,axis load of traffic flow,maintenance history,maintenance fund and maintenance planning goal of highway pavement is constructed,according to Specification for Maintenance Design of Highway Asphalt Pavement(JTG 5421/2018)and other standards.The division method of maintenance section and the decision and optimization technology of maintenance scheme are put forward.(5)According to the model and its corresponding methods and technologies,using big data processing technology and intelligent information processing algorithm,Web open framework Django of Python and its integrated plug-in are used.Combined with GIS technology platform and MySQL database technology management platform,an intelligent decision system for highway maintenance scheme based on B/S architecture is built.Combined with the example test and analysis,the effectiveness and feasibility of all kinds of theoretical methods proposed in this paper are further verified.