Study On The Mechanical Behaviors Of Buried Water Supply Pipelines Under The Coupling Effect Of Nonuniform Settlement And Corrosion

The accidents caused by the water supply pipeline occur frequently,which has a great impact on the safe and stable operation of a city.The water supply pipelines are usually laid underground,and their safety is affected by many factors.However,the current research on the mechanical behaviors of buried water supply pipelines focuses on the influence of a single factor,and there are few studies on the mechanical behaviors of buried water supply pipelines under the coupling of multiple factors.Nonuniform settlement and corrosion are the important factors leading to water supply pipeline accidents.Therefore,the study on the mechanical behaviors of buried water supply pipelines under the coupling effect of nonuniform settlement and corrosion is helpful to improve the active prevention and control capabilities of safety accidents caused by the buried water supply pipelines and ensure the safe operation of urban municipal water supply system.Firstly,the current status of urban water supply system in China is investigated from four aspects of pipe material,pipe diameter,water pressure and buried depth.At the same time,urban tunnel construction and erosion void are selected as the factors that cause the nonuniform settlement of buried water supply pipeline.Secondly,based on the Winkler elastic foundation beam theory,comprehensively considering the influence range of the tunnel construction on the buried pipelines and the law of stratum movement during the construction of the twin tunnels,a new method is proposed to solve the mechanical behaviors of buried pipelines under the construction condition of single or twin tunnels,which is suitable for the calculation of the angle,bending moment and shear force of buried pipelines.And based on the stress state of the pipeline,a method for evaluating the safety status of buried pipelines in the vicinity of urban tunnels is proposed.Thirdly,based on the software ABAQUS,taking buried carbon steel pipes and ductile iron pipes as research objects,the full-circumferential foundation spring model of the buried water supply pipelines is established,which can consider the constraints of the surrounding strata on the pipelines and the erosion void around the pipelines.Then,based on the above numerical model,the influence of the size of the erosion void,the diameter of the pipelines,the wall thickness of the pipelines,the internal pressure of the pipelines,the buried depth of the pipelines,surface load and soil type on the mechanical behaviors of pipelines is analyzed.The results show that erosion void is an important factor affecting the safety performance of buried water supply pipelines.And when the length of the erosion void increases to a certain extent,the axial stress of the pipelines caused by the erosion void will be greater than the hoop stress,and this stress will become the main stress that the pipelines bear.The thickness of pipe wall has a significant effect on the safety performance of buried water supply pipelines.And it is helpful to reduce the safety accidents caused by buried water supply pipelines by increasing the wall thickness of the pipeline and strengthening the anticorrosion measures in the design.Fourthly,taking the buried carbon steel water supply pipelines as the research object,the numerical analysis model of the buried water supply pipelines with corrosion defects is established.And using the above model,the mechanical behaviors of buried water supply pipelines under the coupling effect of nonuniform settlement and corrosion is studied.The failure paths of DN300,DN600 and DN1000 pipelines under different internal pressure,temperature change and corrosion degree are given through the research.The results show that under the coupling action of erosion void and corrosion,the displacement growth rate and stress growth rate of the low internal pressure pipeline are faster.The mechanical behaviors of the above pipelines are different from that under the single action of the erosion void.The pipelines with low internal pressure and high corrosion,and high internal pressure and high corrosion are two types of buried water supply pipelines that are more prone to safety accidents.Finally,based on the above theory,the practical engineering application of municipal water supply network in one park is carried out.The safety status of buried water supply pipelines under the influence of adjacent tunnel construction and erosion cavity and corrosion coupling is evaluated.Some suggestions are put forward for the tunnel construction and the management of urban water supply system in the park.