Research On Interest Coordination Mechanism Of PPP Project Of Utility Tunnel Based On SD-MOP Model

Urban underground utility tunnel is the lifeline of a city to ensure the safe operation of all kinds of municipal pipelines.In recent years,the importance of urban construction has been increasing with the advancement of new urbanization and the increase of urban population.The PPP mode of government and social capital cooperation is mostly used in its investment and construction operation mode.In the process of cooperation,the interests of the government,social capital and corridor pipeline units are different,and the economic interests of all parties are affected by the net present value of profits,financial subsidies and user fees collected during the concession period of the comprehensive corridor PPP project.Therefore,in the PPP model,the concession period of the project,user fees and the government's finance are imperative.Subsidies and other factors are decided or adjusted to achieve the coordination of the interests of all benefit factors.In order to solve the problem of how to coordinate the interests of all parties in the implementation of PPP project,this study first summarizes the benefit factors of the PPP project itself,classifies the participants according to the correlation between the interests of the participants and the interests of the project itself,and chooses the government,social capital and the pipeline units as the three core benefit factors.According to the relevance of interests,the project's own interest factors are corresponded with the core benefit factors to solve the problem of "who coordinates the interests" and "what coordinates the interests".Then,experts are used to score the importance of each benefit factor,and G1 subjective weighting method based on objective correction of standard deviation is used to calculate the index combination weight of each benefit factor,and then calculate the weight of each core benefit factor,that is,the weight of each objective function in the objective model of multi-objective programming,in order to distinguish the importance of the interests of all parties.Then the system dynamics model(SD)and the multi-objective programming model(MOP)are constructed respectively.Based on the system dynamics model of the net present value of income of the PPP project in the utility tunnel,the variable equation is compiled in Vensim DSS software to realize the quantitative calculation of the system dynamics model.Finally,empirical cases are selected to conduct a simulation study,and the inadequacies of the initial case plan in meeting the interests of all participants are found.Then,according to the adjustment relationship among the parameters of financial subsidy,reasonable profit margin,user payment and concession period,and the adjustment scope constrained by the multi-objective programming model,the adjustment schemes under the length of concession period are selected,and the membership functions of the adjustment schemes under the three indicators of total financial subsidy,net present value of project income and total user payment are calculated.The membership degree of each index of the scheme is weighted.Finally,the optimal adjustment scheme is selected to make the interests of the core benefit factors most coordinated.The sensitivity of the optimal adjustment scheme is analyzed,and the differences between the adjustment scheme and the initial scheme are compared,and the optimization of the adjustment scheme on the coordination of interests of all parties is analyzed.The purpose of this study is to provide a reference for the decision-making or adjustment of concession period,entrance pricing,financial subsidies and reasonable profit margin of the comprehensive corridor project,and to provide suggestions on optimizing decision-making for the coordination of interests among the participants who cooperate with PPP model.