The Research Of Seismic Reliability And Isolation Technology For Buried Pipelines Subjected To The Settlement

With the increasing development of the national economy, accelerating the construction of urban modernization,lifeline plays more and more important role in people's daily life,buried pipelines are important component of the lifeline. When earthquake occurs,the ground uneven settlememt lead to the damage of buried pipelines,bring enormous loss of city property and personnel.Therefore,it is necessary to analyze the reliability of buired pipelines to large ground settlement.Mean first-order second moment method,Monte Carlo method-, Response Surface method and Single-factor analysis method are used to calculate the reliability of buired pipelines subjected to the settlement.they will be a base theory for the seismic design and post-reinforcement of buried pipelines subjected to the settlement.Last,isolation technology is to be researched for buried pipeline subjected to the settlement.The main work of this thesis is to deal with the following topics:Boundary condition plays an important role in the calculation of process,good boundary can get accurate results. Firstly, an equivalent spring boundary is brought to analyze the response of buired pipelines subjected to the settlement.Through analyzing an example,get the largest axial stress,the results are very close to the results of fixed boundary condition,it is said that it is reasonable to use the equivalent spring boundary model for analyzing,and also reach the change condition of stress and strain.Then,The First-Order Second-Moment Method and Monte-Carlo Method are used to approximate reliability of buried pipeline, considering the random variables, i.e., displacement of ground settlement, material parameters and internal pressure.By calculating, we obtain that internal pressure has important impact on the axial stress of pipeline,the failure probability is great larger and the reliability coefficient is great smaller which consider internal pressure and the variability of settlement dispalcement has important impact on the reliability of buried pipeline which subjected to the settlement.On both sides of 5 meter department of the interface have a connector in the settlement area and unsettlement area,axial and bend spring are used to simulate pipeline interface material,the equivalent spring boundary is used to analyze the response of four kinds of interface material pipeline which subjected to the settlement.Through the stress-strain curves of pipeline showed that pipeline interface has greater stress and strain concentration phenomenon and due to the presence of pipeline interface,the maximum stress is significantly lower.Firstly,Response Surface method is used to creat the mean and variance of the maximum relative displacement,considering the random variables,i.e., displacement of ground settlement,material parameters and axial spring strength.Then,Single-factor analysis method is used to calculate the reliability of four kinds of interface material pipeline.The results obtained by reliability analysis show that the probability of serious damage of self-stressing cement interface material is the greatest,but the probability of serious damage of aprons asbestos dust interface material.Therefore,the aprons asbestos dust interface material is conducive to anti-seismic for the uncontinuously buried pipeline subjected to the settlement.On both side of the maximum stress and strain point and the point distance 4 meter from the maximum stress and strain point of settlement and unsettlement area set lead rubber bearing which play a role of isolation effect to buried pipeline,it can reduce the earthquake effect of buried pipelin,establish finite element model to calculate.By calculating,we obtain that the maximum compressive stress which set lead rubber bearing is lower 17.24 percent than the maximum compressive stress which not set lead rubber bearing, the maximum compressive strain is lower 13.79 percent. Therefore,it is feasible to use lead rubber bearing to resist seismic for buried pipeline.