西昌MS5.1地震官地大坝实测动力响应特征分析

2018年10月31日16时29分四川西昌发生M_S5.1地震,震中距官地大坝26 km,官地大坝强震监测台阵完整地记录到了本次地震过程。基于官地大坝强震监测台阵记录到的西昌地震强震动数据,通过分析各测点的时程特征、频谱反应规律,研究官地大坝在西昌地震作用下的反应特征和规律。研究表明大坝各部位PGA范围在3.70～69.98 gal,仪器烈度值在1.8～5.2度之间,受西昌地震破裂方向影响,强震动三分向峰值及频谱特性随着高程的增加呈明显的方向性放大效应,总体表现为顺河向分量大于横河向和垂直向分量;此次地震反应周期小于大坝基岩场地特征周期,且西昌地震激励下大坝场地卓越周期与大坝自振周期相差较大,本次地震对大坝安全无影响。

Characteristics of the Measured Dynamic Response of GuandiDam during the MS5.1 Earthquake in Xichang

At 16:29 on October 31, 2018, an M_S5.1 earthquake occurred in Xichang, Sichuan Province. The epicenter of the earthquake was 26 km from Guandi Dam. The earthquake process was completely recorded by the strong motion station on Guandi Dam. On the basis of the recorded strong motion data, the dynamic response characteristics and law of Guandi Dam during the Xichang earthquake are investigated by analyzing the time history characteristics and frequency spectrum response law of each measuring point. Results show that the PGA ranges from 3.70 gal to 69.98 gal in various parts of the dam, and the instrument intensity ranges from 1.8 degree to 5.2 degree. Affected by the direction of the Xichang earthquake rupture, the three-component peak value and spectral characteristics of strong motion show an obvious directional amplification effect with the increase in elevation. Moreover, the overall performance indicates that the longitudinal component is larger than the transverse and vertical components. The response period of the earthquake is less than the characteristic period of the dam bedrock site, and the predominant period of the dam bedrock site under Xichang earthquake excitation is far from the natural vibration period of the dam, indicating that the earthquake has no impact on dam safety.