A Study on Damages of Lifeline Facilities due to Soil Liquefaction

在振动台试验和分析的基础上，研究了地震作用下土壤液化对生命线设施的破坏。回顾了1964年新泻地震和1983年日本集聚地震中土壤液化对生命线设施造成的破坏。据澄清，埋在地下的管道有可能破裂，这不仅是因为震动过程中的动态地面位移，而且也是因为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，了解了永久地面位移的发生机理。位移不发生在液化层和非液化层的交界处，而是在液化层上以恒定的剪切应变发生。由于液化，TIP的弹性模量下降到约1/1000。基于这些试验结果，提出了液化引起的永久地面位移的简化分析方法。为了解模型地埋管与地面之间的摩擦强度，进行了模型地埋管的拉拔试验。测量了不同超孔压比下的摩阻，在液化状态下摩阻达到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。讨论了管道损伤与地面动态位移和永久地面位移之间的关系。

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.