Research On Risk Assessment Of Urban Water Supply Pipeline Network Leakage Based On Unascertained Measure Theory

As one of the basic supply systems for maintaining the normal operation of the city,the water supply network is directly related to the stability of the society and the development of the economy,and is the lifeblood of the city.China is a country with a large amount of water resources but a relatively small amount of per capita possession.With the rapid development of the national economy in recent years,China's urbanization construction is advancing constantly.With this,the contradiction between water supply and demand has proliferated,and the issue of water supply security has become more and more important.How to reduce the leakage rate of the pipeline network and effectively control the leakage loss has become an urgent problem for the society and the water supply enterprise in the case of satisfying the user's demand for water quality and quantity and controlling the water supply cost within a certain range.Urban water supply pipe network leakage control is a systematic project,which involves design,construction,operation and other aspects.Leakage prediction is part of the leakage control and the focus is on preventing it.Studying the risk assessment of pipeline network leakage can improve the management level of water supply enterprises,standardize the collection and collation of pipeline network information,avoid the saturation inspection of pipeline network maintenance in the traditional sense,save manpower,material resources and resources,and make resource utilization efficient.It is of great significance to ensure the safety of water supply and improve the economic benefits of water supply enterprises.Based on the previous research results,this paper combines the water quality hydraulic simulation of EPANET software with the unascertained measure theory as the core,and evaluates the leakage risk of urban water supply pipe network.The main research results are as follows:(1)Analyzed the factors affecting the safety of urban water supply pipe network,and classified according to the influence factors and the positional relationship of the pipeline.The factors mainly include pipe type,pipe diameter,pipe laying time,burial depth,pipe interface form,temperature,soil quality,corrosion(electrochemistry,microbiology),construction water,water supply pressure,pipe network residual chlorine,water hammer and so on.The selection principle of the influencing factors in the evaluation model is determined,and the measurement method of the corresponding leakage rate of different factors is given.Combined with specific cases,it can be found that the smaller the pipe diameter,the larger the leakage rate,and vice versa;the leakage rate of various pipes is from large to small:galvanized steel pipe>gray cast iron pipe>asbestos cement pipe>reinforced concrete pipe>Plastic pipe(PE,PVC,etc.)>Ductile iron pipe;In the initial stage of pipe network construction,the leakage rate is high due to construction reasons,and then the leakage rate increases gradually with the increase of pipe age;The increase of leakage rate shows a trend of decreasing first and then increasing;the ratio of water supply pressure to pipeline pressure capacity is larger,the leakage rate of pipe network is larger;with the increase of residual chlorine content,the leakage rate increases first.The trend of reduction.(2)By establishing a single index measure function,information entropy weighting,calculating a single index measure evaluation matrix,multi-index measure evaluation vector,determining the evaluation level according to the confidence criterion,and calculating the unascertained importance vector to establish the urban water supply pipe network leak The damage evaluation model initially verified the feasibility of the method in a typical case.The method effectively avoids the problem that the weight determination in the fuzzy comprehensive evaluation is subjectively influenced by people;the primary and secondary influences of each factor on the pipe segment are clarified;and the ranking of the pipelines under the same evaluation level is refined.(3)Taking the second section of a city's water supply pipe network as an example of urban pipe network leakage damage,the district water supply pipe network was simplified and merged,and the water supply pipe network structure model was established by EPANET software.The hydraulic quality simulation of the second district pipe network was carried out,the contour map was drawn,the obtained data was verified for conformity,and the valid data was used for the established pipe network evaluation model.The results showed that the C1 grade pipe segment accounted for 3.9%;C2 grade pipe segment accounted for 14.4%;C3 grade pipe segment accounted for 49.7%;C4 grade pipe segment accounted for 20.9%;C5 grade pipe segment accounted for 11.1%,indicating that the overall operation of the pipe network is good,for the analysis of low-grade pipe segment analysis factors The entropy weight is the main influencing factor of tube age,pipe and pressure ratio.On this basis,maintenance measures are proposed.In addition,the S-zone pipe network is divided into four parts,and the leakage pipe sections of each section are counted,and the risk of leakage risk is given,which is consistent with the results of the leakage statistics in the past five years,and the evaluation is verified.The accuracy of the results.(4)Based on MATLAB R2016a,the software system for leakage assessment of urban water supply network was developed.The software analysis results were verified,and the correctness of the software system was proved.It was applied in the case analysis process.The development of the system software greatly saves the evaluation time,and at the same time reduces the mathematical requirements of the engineering personnel in the evaluation process,which facilitates the application and promotion of the evaluation model.