Development of a simplified geophysical exploration system for seismic hazard evaluations

开发用于地震危险性评估的简化地球物理勘探系统

基本信息

批准号：
02555125
负责人：
TOKIMATSU Kohji
金额：
$ 3.2万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-02555125/
关键词：
Rayleigh wave Geophysical exploration Seismic hazard evaluation Shear wave velocity Earthquake Liquefaction Surface wave 被害予測地盤災害予測

项目摘要

An improved version of Rayleigh wave method is presented for the determination of shear wave velocity (V_s) profiles of near surface soils. A dispersion curve and particle orbits of Rayleigh waves can readily be determined in the field through measurements of ground motions induced by an exciter using sensors placed on the ground surface. To determine Vs-profile from the dispersion curve, an inverse analysis is presented in which higher modes and amplitude ratios of particle orbits of Rayleigh waves are taken into account. To increase the effectiveness of the proposed method, desirable distances among the exciter and sensors are indicated. Comparative field tests are made at several sites using the proposed method and the conventional down hole method. The V_s-profiles from the two methods are in good agreement with each other, indicating the effectiveness of the proposed method.Undrained cyclic triaxial tests are conducted using various sands under different confining pressures, to establish a relation between liquefaction resistance and shear wave velocity or elastic shear modulus. The test results together with those of previous studies indicate that the correlation depends on such factors as soil type and confining pressure. Elastic shear modulus is normalized with respect to minimum void ratio and confining pressure, and the test results are re-examined with this value. The normalized shear modulus has a good correlation with liquefaction resistance, irrespective of soil type and confining pressure.Based on the above findings a simplified method is presented for evaluation liquefaction potential of sand deposits using shear wave velocity. Effectiveness of the proposed method is evaluated through field tests at various sites where field performance during earthquakes is known. The estimated results are reasonably consistent with the actual field behavior during the earthquakes, indicating that the proposed method is effective.

提出了一种改进的瑞利波法，以确定近表面土壤的剪切波速度（V_S）轮廓。通过使用放置在地面上的传感器诱导的兴奋剂诱导的地面运动，可以轻松地在现场确定雷利波的分散曲线和粒子轨道。为了确定分散曲线的VS-prolile，提出了反向分析，其中考虑了较高的模式和雷利波颗粒轨道的振幅比。为了提高所提出方法的有效性，指示了激发器和传感器之间的理想距离。使用该方法和常规的下孔方法在多个站点进行比较现场测试。来自两种方法的V_S profiles彼此吻合，表明所提出的方法的有效性。未用的循环三轴测试是使用不同限制压力下的各种砂子进行的，以建立液化耐药性与剪切波速度或弹性剪切模量之间的关系。测试结果以及先前的研究结果表明，相关性取决于土壤类型和限制压力等因素。弹性剪切模量相对于最小空隙比和限制压力进行了归一化，并用该值重新检查了测试结果。归一化剪切模量与液化耐药性具有良好的相关性，无论土壤类型和限制压力如何。基于上述发现，提出了一种简化的方法，用于评估使用剪切波速度的沙子沉积物的液化潜力。通过在地震期间现场性能的各个地点进行现场测试来评估所提出方法的有效性。估计的结果与地震期间的实际现场行为相当一致，表明所提出的方法有效。