Analysis and Measure of Housing Land Deformation Caused by Hyogo-ken Nanbu Earthquake

由于1995年发生兵库-肯南部地震，六面山系统脚下约5 100个地点的住房用地遭到破坏，据评估，5 100个地点中有2 400个地点出于安全原因需要采取一些措施。在本课题中，通过动力响应分析研究了住宅用地变形破坏的原因。首先选择了出现在住房用地上的破损和未破损的地块。在住房用地上，地震后进行了钻探，以了解地下情况。然后，采用反射法进行地震勘探，掌握近地表结构，了解受损场地和未受损场地的剪切波速。结果表明，表层和基岩两层结构为近地表结构，损伤部位的充填体厚度大于未损伤部位。损伤场地的横波速度为130m/S，未损伤场地的横波速度为140m/S。利用输入数据和基于地震勘探确定的边界条件进行了地震响应分析。在本项目中，使用了二维有限元程序Super Flush进行地震反应分析。得到的结果是：1)损伤和未损伤位置的响应加速度相差不大；2)未损伤位置的响应剪应变小于损伤位置的响应剪应变。由此推断，损伤部位可能会产生较大的剪切应变，从而产生变形损伤。

Housing land was damaged at about 5,100 locations in the foot of the Rokko Mountain system due to Hyogo-ken Nanbu Earthquake appeared in 1995, and it was evaluated that 2,400 out of 5,100 locations require some measures for the safety reason. In this project, the cause of deformation-induced damage of housing land is investigated through a dynamic response analysis. Damaged and undamaged sites appeared in a housing land were first chosen. In the housing land, a boring exploration was performed after the quake to know the underground condition. Then, seismic prospecting was carried out with reflection method to grasp the near-surface ground structure, and to know the shear wave velocity for damaged and undamaged sites. As the results, two-layr system, surface layr and base rock, was defined as a near-surface ground structure, and fill was thicher in the damaged site than the undamaged one. The shear wave velocity was obtained as 130m/s for the damaged site and 140m/s for the undamaged site. A seismic response analysis was performed using the input data and boundary condition determined based on the seismic prospecting. In the project, "Super FLUSH" which is a program for two dimensional FEM was used as a seismic response analysis. The results obtained were ; 1) the response acceleration was not so different between damaged and undamaged locations ; and 2) the response shear strain for undamaged location is small in comparison with that for damaged locations. Then, it was deduced that larger shear strain could develop in the damaged locations and that, as a result, deformation-induced damage occurred.