Experimental Study On Mechanical Behavior Of Rubber Gasketed Joint With Ductile Cast Iron Pipe

With the rapid economic development and continuous urbanization process, theunderground pipe network is playing an increasingly important role. However, buriedpipelines may be easily damaged under the actions of earthquakes or other natural disastersand then caused a variety of serious secondary disasters which would bring severely hazardsto citizens’ lives and property. These hidden troubles have become demanding promptsolution problems in disaster prevention and mitigation research field and critically restrict thesustainable development of cities. While in China, most underground pipes do not haveformal seismic design, especially the seismic design of pipeline flexible interface, onlyconsidering a single axial tensile failure mode, but not other kinds of failure modes of thecoupling and the scale effect of pipe diameter. Compared with ground building theory ofseismic design, this design is lagging behind, which is obviously incompatible with theimportant status of the lifeline project of underground pipes. Therefore, strengthening thebasic theoretical study of underground pipelines’ seismic and carrying out study on themechanical property of rubber gasketed joints in segmented pipeline has the importantpractical significances and application values.Based on the comprehensive analysis of present research situation at home and abroadand taking our common water supply system pipe flexible joint ductile iron apron as abreakthrough point, coupled lateral bending test was taken under the action of internalpressure. This paper analyzes failure modes and failure mechanisms of rubber gasketedjoints.The main research work carried out as the following：1. The domestic and international research status of buried pipeline was summarized, acomprehensive analysis of the underground pipeline damage characteristics and seismiceffects was made and the various failure modes and failure mechanisms of flexible pipes weredescribed.2. Directing at currently frequently-used iron pipes, its basic mechanical properties ofmaterials, interface type and using characteristics were summarized and analyzed; theimportance of sealing rubber ring interface was discussed. Meanwhile, the basic mechanicalproperties of rubber materials had been studied. 3. Internal pressure coupled full-scale test for the flexible joint of DN150, DN200,DN300ductile iron apron, which are normally used in public works, was taken; the interfaceunder lateral load force model, failure criteria and a variety of limit state were studied; theinterface and the tube bending stress, axial displacement relationship were analyzed.4. Based on the least squares method, the test data was sorted out and analyzed and thebending pipe interface mechanical model was established. This model is simple and practical,which can be used to estimate the bending force of the pipe interface and to diagnose thesituation of pipe interface on active duty services.5. Depending on the experimental data and based on elastic foundation as a model, aflexible pipe interface nonlinear stiffness matrix equation was established. Thereby, technicalsupport is provided for the numerical simulation of flexible pipes interface.