A Study on Damages of Lifeline Facilities due to Soil Liquefaction

基于振动台试验和分析，研究了地震中土壤液化对生命线设施的破坏。回顾了1964年新泻地震和1983年日本海地震中土壤液化对生命线设施造成的破坏。澄清的是，埋地管道有可能被破坏，不仅是由于震动期间的动态地面位移，而且是由于液化后发生的永久性地面位移。通过振动台试验和室内循环剪切试验，了解地基永久位移的发生机理。位移不发生在液化层与非液化层的交界处，而是在液化层剪切应变恒定的情况下发生。由于液化作用，弹性模量下降到1/1000左右。基于这些试验结果，提出了一种简化的液化永久地基位移分析方法。通过模型埋管在模型地基中的拔管试验，了解了模型埋管与地基的摩擦强度。对不同超孔压比下的摩擦进行了测量，在液化状态下达到了LIP Lo 1/20。结合试验结果，采用“响应位移法”对各种埋地管道的变形和应力进行了数值分析。然后讨论了管道损伤与动力地面位移和永久地面位移的关系。

Damages of lifeline facilities during earthquakes due to soil liquefaction were studied based on shaking table tests and analyses.1. Damages of lifeline facilities caused by soil liquefaction during the 1964 Niigata Earthquake and the 1983 Nihonkai-chtibu Earthquake were reviewed. It was clarified that buried pipelines had possibilities to be broken not only due to dynamic ground displacements during shaking but also due to permanent ground displacements which occur after liquefaction.2. Shaking table tests and laboratory cyclic shear tests were conducted to know the mechanism of occurrence of the permanent ground displacements. The displacements did not occur at the boundary between the liquefied layer and the non-liquefied layer, but occurred with a constant shear strain on liquefied layer. And, the elastic modulus decreased tip to about 1/1000 due to liquefaction. Based on these test results, a simplified procedure for the analysis of the permanent ground displacement due to liquefaction was proposed.3. Pull out tests of a model buried pipe in the model ground were conduct to know the friction strength between the pipe and the ground. The friction was measured under various excess pore pressure ratio, and reached LIP Lo 1/20 in liquefied state.4. The deformation and stress of various kinds of buried pipes was analyzed by using a numerical method, the "response displacement method", considering the test results. Then the relationships between the damage of pipes and the dynamic ground displacements and the permanent ground displacements were discussed.