地下管线的有效应力地震反应分析

Analysis of Seismic Response of Underground Pipelines in Terms of Effective Stress

地下管线的地震反应与管线周围土体的动力特性以及管土之间的相互作用密切相关。在地震作用下,孔隙水压力的发展会导致土体有效应力的降低,并且影响土体的动力特性。根据有效应力方法以及土体的非线性动力本构模型,可以研究孔隙水压力的增长与消散、有效应力的降低以及土动力特性的变化。在地下管线与周围土体之间引入接触单元,来模拟管土之间的接触传递问题;通过有限单元法,对地下管线的地震反应进行了全过程地震反应分析的数值模拟。计算结果表明:在地震作用下,孔隙水压力的增长造成了土体的软化,使得土体的动力特性发生变化,因此管线的地震响应也发生了相应的变化。

Because of remarkable nonlinear behavior and solid-liquid two-phase character of the soil under seismic loads, the soil dynamic properties will be changed significantly. The dynamic intensity and the deformation of soil are mostly depended on the development of pore water pressure. Both of them will influence the dynamic response of the soil-pipeline system. Therefore, the increase of vibrant pore water pressure and the reduction of effective stress should be taken into acount for their effects on soil dynamic properties. On the other hand, the coupling between the dissipation and the re-distribution of pore water pressure and the soil frame response should also be considered. In this paper, the soil surrounding the pipeline is regarded as a solid-liquid two-phase medium. The effective stress method and nonlinear constitutive relation model of soil are used to study the development and the dissipation of pore water pressure during a seismic process. At the same time, the contact interface model is adopted to simulate the interaction between the pipeline and the surrounding soil. Using the program SRUPFE based on the theory of this paper, a numerical simulation of the full-process analysis for an underground pipeline can be gained accurately. From the results of calculations, the development of the pore water pressure leads to the soil softening which causes the change of the soil dynamical characters, and the spectrum identities of soil-pipeline system are also changed. Under horizontal seismic loads, for the stress of pipeline, the axial stress is much more than the flexural stress. Moreover, the seismic response of soil-pipeline system changes with the variation of the soil softening level.