Seismic Response Analysis Of Longitudinal Stress Of Buried Water Pipelines

Buried water pipelines are extremely vulnerable to damage during the earthquake and can cause huge losses to people's lives and property.In the earthquake,the damage of the pipeline joint is the most common.When the longitudinal stress is too large,the joints will be pulled out or crushed,and even causes the ring fractures of the pipelines.There is the interaction of pipe-soil-water for buried water pipelines,and this interaction has a great influence on the dynamic response of the pipelines.In this paper,the longitudinal stress of the pipeline under static load is calculated.Then the dynamic equation of the pipeline under earthquake is established to calculate the longitudinal stress of the pipeline.The main research contents and conclusions are as follows:(1)Combining with the specifications,the longitudinal stress of the pipeline under the effects of ground loading,vertical earth pressure,working pressure,self-gravity,and water gravity is calculated,and the effects,buried depth,site type,pipe diameter,wall thickness and working pressure,for the longitudinal stress of buried pipelines are analyzed.(2)Based on the Hamilton principle,considering the interaction between pipe and soil,the dynamic equation of the pipeline without water under earthquake is established by combining finite element method.The longitudinal stress of the pipeline is calculated by programming with MATLAB,and the influences,buried depth,site type,pipe diameter,wall thickness,calculated length and seismic wave,on the the seismic response of the longitudinal stress are analyzed.The results showed that: the change of the longitudinal stress lags behind the change of the seismic displacement in different depths,site types,diameters,wall thicknesses,calculated lengths and seismic waves,and longitudinal stress peaks vary with above factors.(3)Based on the Hamilton principle,considering the interaction of pipe-soil-water,the dynamic equation of the pipeline with water under earthquake is established by combining finite element method.The longitudinal stress of the pipeline is calculated by programming with MATLAB,and the influences,buried depth,site type,pipe diameter,wall thickness,calculated lengths,working pressure,flow velocity and seismic wave,on the seismic response of the longitudinal stress are analyzed.The results showe that: the change of the longitudinal stress lags behind the change of the seismic displacement in different depths,site types,diameters,wall thicknesses,calculated lengths,working pressures,flow velocities and seismic waves,and longitudinal stress peaks vary with above factors;the peak value of the longitudinal stress in the upper part of the pipe decreases with the increase of the working pressure,and the peak value of the lower longitudinal stress increases with the increase of the working pressure;the influence,different flow velocities,on the seismic response of the longitudinal stress is small.(4)There is a comparative analysis about the longitudinal stress of pipelines with water and pipelines without water.For pipelines with water and pipelines without water,the bending stress peaks become smaller and the axial stress peaks are approximately equal.The reason is as follows: There is the interaction of pipe-water.This interaction will reduce the bending stress,but it has less influence on the axial stress.The above research methods and conclusions can provide references for related theoretical researchs or engineering applications,and can provide lessons for the further study on the seismic design of pressure pipelines,for example,buried oil pipelines and buried gas pipelines.