Cyclic behavior of clay during great earthquake and its consititutive model

液化已被认为是1995年小府南部地震造成地面破坏的重要因素。众所周知，在大阪等日本城市周边地区有大量软粘土沉积物。为了准确地厘清地基的抗震能力，有必要厘清小府南部7级地震等强震作用下软粘土沉积的动力行为。因此，本研究的重点是建立粘土的动力特性模型。该模型既适用于1%左右的小应变，也适用于10%以上的大应变。为此，在粘土上进行了循环三轴和扭转试验。在试验结果的基础上，利用非线性运动硬化规律建立了循环粘塑性本构模型。为了描述小应变下高频域的能量耗散特性，本文提出了粘弹性-粘塑性模型。最后，利用1995年小古根-南部地震在港岛观测到的加速度记录进行一维模拟，研究了粘土的粘弹性和粘塑性特性对含粘土层的地基动力性能的影响。

Liquefaction has been recognized as an important factor of ground damage due to 1995 Hyogoken Nambu Earthquake. It is well known that soft clay sediment are deposited around Japanese urban area such as Osaka city. In order to accurately clarify the ability of the earthquake resistance of ground, it is necessary to clarify the dynamic behavior of soft clay deposit due to the great earthquake such as Hyogoken Nambu Earthquake which is magnitude 7 in Richter scale.For this reason, the present study focuses on the modeling of dynamic behavior of clay. The model proposed is applicable to the behaviors both at small strain around 1% and at the large strain more than 10%. For this purpose, cyclic triaxial and torsional tests have been performed on clay. Based on the experimental results, a cyclic viscoplastic constitutive model has been developed using the non-linear kinematic hardening rule. In the study, a viscoelastic- viscoplastic model has been newly proposed in order to describe energy dissipation chracteristics in high frequency domain at a small strain. Finally, by the one-dimensional simulation with the observed acceleration records at Port Island during the 1995 Hyogoken-Nambu Earthquake, the effect of viscoelastic and viscoplastic property of clay on the of dynamic behavior of ground including clay layers is studied.