The Finite Element Analysis For Mechanical Response Of Buried Thermal Pipeline In Liquefied Soil

As one of the main components of lifeline engineering,thermal pipelines have a great contribution to people's lives and industrial production.Once the thermal pipeline is destroyed,it will threaten urban safety and do harm to people's lives and properties.Seismic waves in the liquefaction site will have a horizontal and vertical loading on the buried pipeline,and at the same time the buried pipeline will deforme in vertical plane because of flotation response.The most serious situation is that the buried pipeline is exposed to the ground.The forces on the pipeline are very complicated when the thermal pipeline is in the liquefaction site,such as the pipe-soil contact,the flotation caused by the soil liquefaction and the thermodynamic coupling between the pipe and the internal heat medium.Therefore,it is extremely important to establish a model under multicoupling.An analytic model of pipe soil contact-soil spring-thermodynamic coupling for the mechanical response of buried pipeline in liquefied soil was established by using finite element analytical software ADINA.The flotation displacement,axial and circumferential stress and strain of the buried thermal pipe were analyzed under a variety of effects,especially the effect of thermodynamic coupling.Results show that flotation displacement of pipeline is larger under both floating effect of the liquefied soil and the thermodynamic coupling effect between the pipe and the internal heat medium.That is,the flotation displacement of the pipeline gradually increases with the increase of the internal temperature.So thermodynamic coupling can increase the flotation response of buried thermal pipeline,and make the pipeline more prone to damage.By analyzing the flotation displacement,axial and circumferential stress and strain of buried thermal pipeline,the flotation displacement is larger and the pipeline is easier to be damaged seriously with the larger diameter of pipe and density of liquefied soil,the smaller depth and thinner wall of buried pipeline.The location of the maximum stress on the pipe is at the interface between the liquefaction zone and the non-liquefied zone.