NEESR-II: Study of Surface Wave Methods for Deep Shear Wave Velocity Profiling Applied to the Deep Sediments of the Mississippi Embayment

摘要本课题的主要目的是研究低频表面波非侵入式测量极深沉积物横波速度剖面的测试方法。表面波方法已成为现场响应研究中表征土壤沉积物的公认方法，并且与已建立的钻孔方法相比效果良好。目前存在几种有源表面波方法，它们具有不同程度的复杂程度和效率。然而，这些方法都没有被研究应用于沉积物的极深剖面（300米或更深）问题。在过去的20年里，大多数研究都集中在30米的顶部，很少有研究延伸到100米以外的深度。随着地震工程模拟网络（NEES）大型现场振动筛的出现，现在可以主动产生低频能量（低至1.0 Hz），这是非常深的土壤剖面所需要的。将在美国中部的几个地点进行实地研究，使用各种数据收集和数据处理方法。这项工作的发现将适用于全国各地地震活跃地区的其他深层土壤地点，包括犹他州的盐湖城、加利福尼亚州的洛杉矶和南卡罗来纳州的查尔斯顿。从这些研究中得出的深部VS剖面将填补密西西比海湾深部土壤刚度结构知识现状的空白，从而提供额外的好处。预测这个地震活跃地区的地面反应需要了解深层沉积物结构，在某些地区，这种结构可以延伸到1000米深。由于缺乏对深层土体刚度结构的认识，近年来对该地区地基响应的研究受到限制。虽然近地表沉积物（顶部30米）通常具有很好的特征，但对超过100米的深度进行的测量很少。在这些研究中所测得的VS剖面，将成为研究该地区地盘反应的重要输入参数。这项工作的发现将通过同行评审的出版物传播给工程界。此外，数据集将被放置在NEES存储库中，并将成为该领域其他研究人员的宝贵资源。教育领域模块，展示重要的概念，如场地共振和土壤液化，将由本科生开发。这些实地教育模块将包括在向美国中部农村和少数民族K-12学生演示这种最先进的实地测试设备中。

ABSTRACTThe primary objective of this research project is to study testing methodologies for non-intrusively measuring shear wave velocity (VS) profiles of very deep sediments using low-frequency surface waves. Surface wave methods have become an accepted means to characterize soil deposits for site response studies and have compared well to established borehole methods. Several active-source surface wave methodologies, having varying degrees of sophistication and efficiency, currently exist. None of these methods, however, has been studied for application to the problem of very deep profiling (300 m and greater) of sediments. Most studies in the last 20 years have focused on the top 30 m with very few studies extending beyond a depth of 100 m. With the advent of the Network for Earthquake Engineering Simulation (NEES) large-scale field shakers, it is now possible to actively generate the low-frequency energy (down to 1.0 Hz) that is required for very deep soil profiling. Field studies will be conducted at several sites in the Central United States using a variety of data collection and data processing methodologies. The findings from this work will be applicable at other deep soil sites in seismically active regions around the country, including Salt Lake City, Utah, Los Angeles, California, and Charleston, South Carolina. The deep VS profiles derived from these studies will provide an additional benefit by filling a gap in the current state of knowledge of the stiffness structure of the deep soils of the Mississippi Embayment. Predicting the ground response in this seismically active region requires knowledge of the deep sediment structure, which extends to depths of 1000 m in some areas. Recent studies of the ground response in this region have been limited by a lack of knowledge of the deep soil stiffness structure. While the near-surface sediments (top 30 m) are generally well characterized, very few measurements have been performed to depths greater than 100 m. The VS profiles measured during these studies will be important input parameters for site response studies in this region. The findings from this work will be disseminated to the engineering community through peer-reviewed publications. Also, data sets will be placed on the NEES repository and will be a valuable resource for other researchers in this field. Educational field modules, demonstrating important concepts such as site resonance and soil liquefaction, will be developed by undergraduate students. These field educational modules will be included in demonstrations of this state-of-the-art field testing equipment to rural and minority K-12 students in the Central United States.