Seismic Response Characteristics Of Buried Bends And Connectivity Of Water Supply Pipeline Network Based On Monitoring

Earthquake has been distracting the structures of cities.Now adays,numbers of pipeline damages are happiening in cities evey year due to ground shakings.Water supply,oil and natural gas pipelines,which carry materials are vital to the maintenance of life,and are usually called “lifelines”.The important feature of underground pipeline network is that it spans different geological units,which is more vulnerable to the threat of geological disasters.The relative movement between the pipeline network and the soil is usually small,and the transient and permanent ground deformation will affect the entire pipeline network.The study on seismic response of underground pipelines has always been the focus of lifeline seismic engineering research.Existing results show that the most direct cause of pipeline failure is the pipe-soil interaction,and this research can only be based on a single pipe section.Therefore,how to apply these research contents to the calculation of pipeline network connectivity,that is,to realize the analysis system of“node-network-application” three dimensions is the problem that this paper faces.In order to satisfy the previous underground buried pipeline network problems,the elbow and pipeline network under seismic action was chosen as a research topic in this paper.The law of pipe-soil interaction and response mechanism of elbows were systematically investigated.And the interaction analysis between the nodes of the pipeline network was carried out.Finally,the vulnerability calculation method of pipe section and the connectivity calculation method of pipeline network based on Copula function were proposed.The specific work carried out in this paper is as follows:1.Shaking table test of buried elbow and small scale pipeline network.In this test,the PVC-U pipe material was used,and the prototype pipeline was designed according to the similarity ratio conversion.And the influence factors of the soil properties,as well as the buried depth,pipe diameter,elbow angle,bending radius and seismic wave peak value were taken into consideration.Three different excellent frequency seismic waves were loaded.Earth pressure,strain,acceleration and shear box displacement response were collected.The accuracy of the test results was demonstrated by using the elastic foundation beam theory.2.Pipe-soil interaction simulation and test results analysis of multiple types of pipe sections.Firstly,this study combed and summarized the research results of scholars on pipe-soil interaction,and explored the optimal contact theory to describe pipe-soil interaction,the empirical formula recommended by the ASCE guidelines.Then,three numerical contact models were established,and compared with the test results.The model that was most suitable for describing the pipe-soil contact was summarized.According to the most practical contact model,the changes of earth pressure,friction,strain and relative displacement with depth were studied.According to the shaking table test of elbows and tees,the earth pressure under different buried depths,pipe diameters,bend angles,seismic waves and peaks was studied;the earth pressure at the elbow and the earth pressure of the straight pipe were fitted,and the empirical fitting formula for the earth pressure at the elbow was obtained.And the change trend of the earth pressure of the elbow was summarized,and the influence coefficient of the earth pressure of the elbow based on the earth pressure of straight pipe was obtained.Then,in the same way,the variation of earth pressure of the tee was studied.Subsequently,the fitting formula of the pipe-soil deformation transfer coefficient at the elbow was studied.This formula comprehensively considered the bending angle,buried depth,pipe diameter,wall thickness and other factors of the elbow.Then,on the basis of the fitting formula of the deformation transfer coefficient at the elbow,the fitting formula of the deformation transfer coefficient at the tee was studied.Finally,the earth pressure and deformation transfer coefficient were simulated by two numerical contact elements,which verifies the applicability of Goodman contact element to elbows and tees without separation between pipe and soil.3.The interaction analysis of pipeline network nodes under the seismic action.Firstly,the axial strain along the vibration direction of seismic wave was used to analyze the friction force,bending deformation,deformation amplification coefficient and pipe-soil relative displacement.Then,the axial deformation and relative displacement of the pipeline were analyzed according to the earth pressure and acceleration of the scaled pipeline network,which was compared with the analysis results based on strain.Then,the results of scale pipeline network were compared with the axial strain,earth pressure and acceleration test results of H-shaped and Z-shaped pipes respectively.Finally,the regularities of mutual influence among pipeline network nodes were obtained.The increase of elbow or tee for pipeline network will aggravate the deformation incoordination at the pipeline network nodes,making the joints more prone to damage.4.Research on vulnerability analysis based on series-parallel system of Copula function and connectivity decision evaluation of pipeline networks.Firstly,the deformation amplification coefficient of the pipes through the basic data obtained from the shaking table test was calculated,and based on the two-parameter log-normal distribution function,the probability seismic demand of the pipes was obtained.Then,the theoretical seismic vulnerability curve of the scale pipeline network was established.In this study,Copula function technology was introduced to simulate the correlation between components,and the seismic connectivity analysis method of pipeline network system based on series-parallel combination system was proposed.For the connectivity decision evaluation of actual large-scale complex pipeline network,firstly,based on the results of shaking table test,the initial reliability of various types of pipe sections and nodes was determined,and the reliability adjustment rules of pipe sections under the Copula function and the reliability adjustment strategy based on earth pressure and deformation transfer coefficient were proposed.Then,based on previous calculation methods of pipeline network connectivity,the minimum path recursive decomposition algorithm considering nodes such as elbows and tees was derived,and the adjustment strategy of network connectivity and reliability was proposed,which laid the foundation for further accurate calculation of pipeline network connectivity.5.Case calculation and development of decision-making platform for pipeline network connectivity.Firstly,normalized the data table format,spatial elements and operation management data of pipe network system.Then the research on the basic database of safe operation of water supply and drainage pipeline network and the decision-making implementation plan of pipeline network system connectivity were carried out.Based on this plan,the connectivity of buried water supply pipeline network system in Suzhou Industrial Park was calculated more accurately.It provides a basis for the key monitoring of most potential failure probabilities of pipeline network.Finally,a water supply and drainage system technology platform for connectivity decision-making and intelligent monitoring under earthquake disaster was established based on GIS.