液化土中管道随机地震响应分析与可靠度评价研究

Stochastic seismic response analysis and reliability evaluation of pipelines in liquefied soil

地震作用下饱和砂土液化会导致埋地管道上浮,引起系统功能失效。为探究液化场地中埋地管道的地震响应和可靠度水平,充分考虑地震动的随机性和非平稳性,提出了基于概率密度演化法和等价极值分布的概率分析方法,从超孔隙水压力、加速度和结构位移变形三方面对埋地管道进行随机动力分析和可靠度评价。结果表明:地震动的随机性对埋地管道的动力响应有显著影响,传统的确定性分析方法可能会低估管道的地震响应,提出的分析方法能较全面地研究管道的上浮机理和可靠度水平;地震作用下,孔隙水压力上升,导致土壤有效应力下降,进而发生土壤液化是管道上浮的主要原因;两侧土壤向管道底部的挤压和指向管底的渗流压力进一步加剧了管道的抬升。最后,基于成灾机理研究了U型碎石排水对埋地管道的减灾效果和机理。提出的随机概率分析方法,可以对管道的上浮机理和可靠度做出较为准确的分析。

The liquefaction of saturated sand under the action of earthquakes can cause the buried pipeline to float up and the system failure.To investigate the seismic response and reliability level of buried pipelines in liquefaction sites,a probabilistic analysis method based on the probability density evolution method and equivalent extreme value distribution is proposed to fully consider the randomness and non-stationarity of ground shaking.According to the excess pore water pressure,acceleration and displacement of structures,the random dynamic analysis and reliability assessment of the buried pipeline are carried out.The results show that the randomness of ground motion has a significant effect on the dynamic response of buried pipelines,and the traditional deterministic analysis methods may underestimate the seismic response of pipelines.The proposed method can be use to comprehensively study the floating mechanism and reliability level of buried pipelines.Under the action of earthquakes,the pore water pressure increases,which leads to a decrease in the effective soil stress,and then liquefaction of the soil occurs,causing the pipe to float up.The compression of soil at both sides towards the bottom of the pipe and the seepage pressure towards the bottom of the pipe further aggravate the uplift of the pipe.Finally,the disaster mitigation effect and mechanism of U-shaped gravel drainage on buried pipelines are studied based on disaster mechanism.The proposed stochastic probability analysis method can be employed to accurately evaluate the buoyancy mechanism and reliability of pipelines.