Development of Liquefaction Detective Sensor Installing with Strong Ground Motion Accerelometer

本研究的重点是监测地面运动，以检测液化。1995年日本兵库县南部大地震后，人们认识到监测系统在生命线地震工程中的重要性。生命线地震工程的监测系统分为两个方面。一个是生命线设施的监测，另一个是地面运动和地面破坏的监测。本研究的重点是利用地震动监测来检测液化，尝试利用强震记录来检测液化。首先，研究了强震记录的幅值特性。根据液化区和非液化区地表的反应加速度记录，计算了竖向地面加速度与水平地面加速度之比的时程。如果在每个时间步计算垂直地面加速度与水平地面加速度的比值，当水平地面加速度瞬时接近零时，该比值明显较大。因此，为了避免瞬时大值，根据每0.3秒的最大加速度计算比率。其次，研究了响应加速度记录的频率特性。计算了强震的平均卓越频率和卓越频率的下降率。最后，利用1999年台湾集集地震和2000年西武鸟取县地震等100多个地面反应加速度记录对这些指标进行了验证。

The present study is focusing on the monitoring of ground motion in order to detect liquefaction. The importance of monitoring system was recognized in the lifeline earthquake engineering after the 1995 Hyogoken Nambu earthquake in Japan. The monitoring system in the lifeline earthquake engineering is classified into two aspects. One is the monitoring of lifeline facilities and the other is the monitoring of ground motion and ground failure. The present study is focusing on the monitoring of the ground motion in order to detect liquefaction.The study tries to use the strong ground motion records for detection of liquefaction. First, amplitude characteristics of strong ground motion records were investigated. Time histories of ratio of vertical ground acceleration to the horizontal one was calculated from response acceleration records at ground surface in liquefied and non-liquefied areas. If the ratio of vertical ground acceleration to the horizontal one is calculated at each time step, the ratio is remarkably great when the horizontal ground acceleration is close to zero instantaneously. Therefore, the ratio was calculated from the maximum accelerations for every 0.3 seconds in order to avoid the instantaneous great value. Next, frequency characteristics of the response acceleration records were studied. The average predominant frequency of the strong motion and decrease rate of the predominant frequency was calculated. Finally these indices were verified by using more than one hundred response acceleration records at ground surface including the 1999 Ji-Ji Earthquake in Taiwan and 2000 Tottoriken Seibu Earthquake.