Evaluation of Aseismic Resistance of Pipeline Strucure Subjected to Large Ground Deformation

本研究的目的是阐明埋地管道在地面大变形作用下的非线性行为特征，评估管道在液化环境下的抗震抗力，以便建立有效的抗震设计模型。特别针对强地震动作用下土体液化引起的地面大变形，进行了液化土体地面大位移的室内试验，建立了埋地管道及其接头的地震反应分析方法。利用砂箱模型管道在振动台上进行了液化试验。根据剪切应变、孔压和加速度的计算结果，研究了土壤液化过程中管道-地面系统恢复力的非线性特征。并对土体液化引起的侧向流动进行了试验研究。建立了基于二维有限元地基势头法的液化侧向流分析方法，数值计算了几种表层模型的地面大位移量，以及含接缝的埋地管道在这种地面变形作用下的位移和内力响应，包括挤密砂桩和板桩的对策方法。通过将分析结果与实验或测量结果进行比较，证实了这些分析方法的准确性。对影响管道抗震设计的重要参数，如管道倾角与表层厚度、管道与接头参数、地基处理条件与地面大变形之间的关系进行了评价，得出了有益的结论。

Objects of this study are to clarify the non-linearly behavior characteristics of buried pipeline subjected to large ground deformations and to evaluate the aseismic resistent force of the pipelines during liquefaction environment for the effective aseismic design model. Particularly we focussed on the large ground deformations induced by soil liquefaction during strong ground motion and performmed laboratory test for the large ground displacement of liquefied soil and built up the analytical method for seismic response of buried pipeline including its joints. Liquefaction tests using the model pipeline in sand box on the shaking table are performed. From the results of shear strains, pore pressures and accelerations the non-linearly characteristics of restorning forces of pipeline-ground system during soil liquefaction are investigated. Experiment for the lateral flow induced by soil liquefaction is also performed. Analytical method for the lateral flow induced by liquefaction was developed based on the potential head method of the ground by 2 dimensional FEM.Numerical computations for the large ground displacements of the several surface layers models and the responses of the displacements and internal forces of the buried pipelines with joints subjected to such ground deformations are performed including the countermeasure method of the sand compaction piles and sheet piles. Accuracy of these analytical methods is confirmed by comparing the analytical results with the experimental or measured results. The relations between the important parameters for aseismic design of pipelines, such as the inclined angle and the thickness of the surface layer, the parameters of the pipeline and the joints, the conditions of the ground improvements and the large ground diformations, are evaluated and the useful results were obtained.