Study On The Effect Of Site Subsidence On Buried Pipeline

A lot of buried pipelines have been destructed by the stratum subsidence, which is caused by the earthquake. In order to guarantee its'security and normal service, It is significant to study the influence of settlement region to the buried-pipeline.The buried-pipeline in the settlement region has been simulated by the finite element software ANSYS. Nonlinear analysis is considered, geometric gross distortion nonlinear, material nonlinear and contact nonlinear. The following points are discussed in this thesis:1. Some seismic research achievements of buried pipeline are summarized and the research status on response analysis of buried pipeline in settlement region is introduced. Based on this idea, the research method and research target is put forward.2. The advantages and disadvantages of theories on various numerical models are analyzed. Based on the analysis, D-P model is used for soil body, shell model is used for pipeline, contiguity model is used for pipe-soil interaction and three-dimensional models are used for the system which is composed of soil and pipeline.3. The basic ideas of numerical simulation by the finite element software ANSYS is introduced. The realization of nonlinear in ANSYS,the choose of element type,the effective calculation area,the method of confirming boundary conditions and the establishment of pipe-soil interaction model are included. The settlement region is realized by such method in this research: The soil under a certain area is dug hollow, and the response of soil under self weight is simulated. The funnel-shaped effect of ground settlement which is caused by earthquake is realized, and the deformation of soil is continuous. Though simulation and trial calculation, the effects of ground settlement is in accord with the fact.4. The response of pipeline is influenced by a series of conditions, which include material properties, amount of seismic subsidence, dimension of settlement area, the depth of pipeline buried, the same and the different diameter-thickness ratio. The effects of a series of model parameters to the response of pipeline are studied, and some meaningful results have been obtained. 1)The different responses of pipeline in settlement region are showed because of different soil property. 2)The more amount of seismic subsidence,the larger response of pipeline is. But when the amount of seismic subsidence is at a certain value, the change of response of pipeline is very little.3)When the dimension of settlement area is at an appropriate range, destruction influence to the pipeline is largest. 4)The more shallow the pipeline buried, the larger the additional stress and additional strain is. 6)The destruction influence of settlement region to the pipeline is increased with the larger diameter-thickness ratio. 6)The destruction influence of settlement region to the pipeline is increased with the smaller diameter, when the diameter-thickness ratio is in the same size.5. The study is summarized and analyzed, and the research need to be done next is presented.The important reference value for seismic design of pipeline in settlement region is provided by the research results.