Damage Evaluation System of Soils in Subsurface Layers of Ground Using Identification Method

本研究的目的是提出一个将识别方法与剪切应变计算相结合的地面沉积层土壤震害评估的系统程序。本文提出了一种新的沉积层频率相关品质因数模型Q(F)，Q(F)=Qo/(1+a exp(-b(f-fo)^2))，其中Qo、a、b和fo是品质因数的频率依赖性参数，f是频率。将品质因数模型引入到地下各层S波速和品质因数的识别程序中。对以往使用的识别程序进行了改进，以考虑地下地基各层品质因数的频率相关性。编制了利用垂直台阵记录确定的S波速和品质因数计算地下各层剪切应变的程序。将识别程序与剪切应变计算程序连接起来，构建了各层土体震害评估的系统程序。利用日本9个测点的垂直台阵记录进行了数值分析，结果表明，软土中的最大剪应变约为5×10~(-4)，记录的最大加速度为100 cm/s^2。

The objective of this study is to present a system program for evaluating the earthquake damage of soils in sedimentary layers of ground, in which identification method and calculation of shear strain are connected. In this study, a new model of frequency-dependent quality factor in sedimentary layers, Q(f), is presented as follows.Q(f) = Qo / (1 + a exp(-b(f-fo)^2))where Qo, a, b and fo are the parameters which prescribe the frequency-dependency of quality factor, and f is frequency. The model of quality factor is introduced into identification program for S-wave velocity and quality factor of each layer in subsurface ground.The results in this study are summarized as follows.1. The identification program, which was used previously, has been improved, in order to consider the frequency dependency of quality factor of each layer in subsurface ground.2. The program has been developed for calculating the shear strain in each layer of subsurface ground, using the S-wave velocity and quality factor identified from vertical array records. The system program for evaluating the earthquake damage of soils in each layer has been constructed by connecting the identification program and the program for calculating shear strain.3. The numerical analyses are carried out using vertical array records at 9 sites in Japan, which show that the maximum shear strain is about 5_x10^<-4> in soft soil, where the maximum acceleration of record is 100cm/sec^2.