埋地管线腐蚀模型及地震随机反应分析

埋地管线在使用过程中会出现不同程度的腐蚀现象。由于管线腐蚀受到周围土壤性质、输送介质等不确定因素的影响,其腐蚀状态会呈现随机性的特点。本文利用带吸收壁的齐次马尔可夫链理论,提出了管线腐蚀发生的离散状态模型,并根据管线腐蚀线性发展模型,推导给出了管线截面面积随时间变化的概率模型。在此基础上,利用弹性地基梁原理建立了管线地震反应的表达式,并利用M on te-C arlo随机模拟方法进行了模拟分析。实例分析表明,本文建立的腐蚀模型可以较好地模拟埋地管线的腐蚀现象,并能获得在地震激励下腐蚀管线的随机反应。

A Corrosion Model of Buried Pipeline and Stochastic Response of Pipeline under Earthquake

Corrosion will appear inside and outside of buried pipelines gradually as the service time increases. However, as the characteristics of the soil around the pipeline and the conveying material inside the pipeline are undetermined, the corrosion state of buried pipeline must be stochastic. In this paper, homo geneous Markov chain with absorbing barrier, an effect mathematics tool for simulating the evolution of system with discrete states, is used to simulate the occurrence of corrosion on the pipeline. Combined with linear corrosion development model, the probability distribution of the pipeline section area is derived. On the basis of above corrosion model of pipeline, elastic foundation beam method, a classical elastic method for analyzing the seismic response of pipeline subject to seismic wave propagation, is used to express the seismic displacement and stress of pipeline as the function of the random variable, pipe segments section areas. Then by use of Monte Carlo random simulation method, the mean and standard deviation of the seismic response of the pipeline are obtained. In order to validate the proposed model, a 100 meters long pipeline, whose diameter is 325 mm and thick is 16 mm, is investigated in detail. First, the probability distribution of the pipeline section area is obtained after it has served 50 years. Then, the mean and standard deviation of the pipeline displacement and stress are obtained subject to a real seismic wave. The resuits indicate that the proposed approach can efficiently simulate the corrosion state of the buried pipeline. Also, from the random seismic response of the pipeline, it is found that the variability of the pipeline section area is almost same as that of the pipeline seismic stress and that the corrosion has littlie effect on the variability of pipeline seismic displacement.