Cyclic behavior of clay during great earthquake and its consititutive model

液化已被认为是1995年日本南部地震引起的地面破坏的一个重要因素。众所周知，日本大阪市等城市周围都有软粘土沉积。为了准确地阐明地基的抗震能力，有必要弄清在日本南部7级地震等大地震作用下，软粘土地基的动力特性，为此，本文的研究重点是粘土的动力特性模拟。该模型既适用于1%左右的小应变，也适用于大于10%的大应变。为此，对粘土进行了循环三轴和扭转试验。在试验结果的基础上，采用非线性运动硬化准则建立了循环粘塑性本构模型。在研究中，新提出了一种粘弹-粘塑性模型来描述小应变下高频域的耗能特性。最后，通过对1995年日本地震中港岛的加速度观测记录的一维模拟，研究了粘土的粘弹和粘塑性对含粘土层的地基动力特性的影响。

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.