Collaborative Research: Bridging the In-situ and Elemental Cyclic Response of Transitional Soils

合作研究：弥合过渡性土壤的原位和元素循环响应

基本信息

批准号：
1663531
负责人：
Kenneth Stokoe
金额：
$ 48.84万
依托单位：
University of Texas at Austin
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-07-01 至 2021-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1663531&HistoricalAwards=false
关键词：
Collaborative Research Bridging situ Elemental

项目摘要

The consequences of earthquake-induced liquefaction are not trivial; for example, $15B of damage was attributed to soil liquefaction resulting from the recent Canterbury Earthquake Sequence in New Zealand. Large portions of the United States, from Alaska to California and eastward to the New Madrid Seismic Zone and coastal South Carolina and north to the St. Lawrence Seaway, are prone to the impacts from earthquakes. Earthquakes such as those in New Zealand and others have raised awareness about limitations in our understanding of the cyclic response of natural soil deposits. These limitations have arisen through continued use of the traditional practice of simplifying geotechnical analyses by considering two main soil types: drained sands and undrained clays. Design methodologies for nearly all geotechnical systems have developed along these two distinct lines. However, many natural soil deposits do not fit into these simple categories; transitional silty soils, the subject of this research, are an example. This study aims to answer pertinent questions concerning the cyclic response of transitional silty soils through systematic and coordinated field and laboratory studies that will improve our understanding of the potential for large deformations and loss of life and property during large earthquakes. The findings of this research will have broad application across the nation and globe. Furthermore, this research will have a parallel objective of inspiring the next generation of STEM leaders. Collaboration with the Hatfield Marine Science Center (HMSC) in Newport, Oregon will allow our outreach efforts to reach 150,000 visitors and 40,000 K-12 students and teachers per year, through: (1) public demonstrations of liquefaction and in-situ cyclic tests with a large mobile shaker truck, (2) a compilation of video demonstrations, data, and interviews with the researchers into a permanent interactive exhibit, and (3) development of instructional modules for HMSC staff to help their established outreach effort expand instruction to include coastal hazards such as the Cascadia Subduction Zone and associated tsunami. The demonstrations will be leveraged to form permanent exhibits and instructional modules, which will greatly extend this outreach effort.This research will improve our understanding of the in-situ and laboratory cyclic response of silt soils including nonlinearity, degradation of stiffness, triggering of destabilizing excess pore pressures, and the corresponding post-shaking consequences. Specifically, this study will: (1) narrow the threshold fines content and plasticity separating "sand-like" and "clay-like" responses to cyclic shear stresses/strains and identify critical threshold states; (2) compare the in-situ, uniaxial and biaxial cyclic response of transitional soils to understand how changes in strong ground motion directionality impacts generation of pore pressure and volumetric strain; (3) determine the effect of soil fabric, stress history, and degree of saturation on the cyclic and post-cyclic response of transitional soils; (4) link the regional findings from this work to previous efforts on transitional soils; and (5) inspire future seismologists, geologists, earthquake engineers, and natural hazard and resilience planners through a long-lived, coordinated outreach program. This work concentrates on experiments that target small-to-large shear strains, using techniques that range from in-situ cyclic loading from large mobile shakers and blast liquefaction, to specialized and coordinated laboratory tests, allowing the development of an unprecedented dataset critical for improving the understanding of the in-situ and elemental level cyclic response to be bridged.

地震引起的液化的后果并不小。例如，新西兰坎特伯雷地震序列最近造成的土壤液化归因于15b损失。从阿拉斯加到加利福尼亚州，向东到新的马德里地震地区和南卡罗来纳州沿海地区，再到圣劳伦斯海道，美国的大部分地区都容易受到地震的影响。诸如新西兰和其他人等地震已经提高了人们对我们对天然土壤沉积物循环反应的局限性的认识。通过继续使用两种主要土壤类型来简化岩土分析的传统实践，从而产生了这些局限性：排水沙子和未排水的粘土。几乎所有岩土技术系统的设计方法都沿着这两条不同的线条开发。但是，许多天然土壤沉积不适合这些简单类别。这项研究的主题是过渡性粉质土壤。这项研究旨在通过系统和协调的现场和实验室研究来回答有关过渡性粉质土壤循环反应的相关问题，这将提高我们对大地震期间大变形以及生命和财产丧失的潜力的理解。这项研究的发现将在全国和地球上广泛应用。此外，这项研究将具有启发下一代STEM领导者的平行目标。与俄勒冈州纽波特的Hatfield海洋科学中心（HMSC）合作，我们的宣传工作每年可以吸引15万名访客和40,000 k-12的学生和老师，通过以下方式：（1）公开演示液化和液化环境测试，并与大型移动振动器卡车一起进行液化和式循环测试，（2）与视频示范的介绍（3）进行了研究（2）研究（2）研究（2）研究（3）研究（3），研究（3）研究（3）研究（3）研究（3）研究（3），研究（3）研究（3）研究（3）研究（3）研究（3）研究（3）研究（3）研究（3）研究（2）研究（3）研究（3）研究（3）研究，以及研究（3）研究，研究（3）研究（3），研究（3）访问的研究（3） HMSC工作人员的模块，以帮助他们既定的外展工作扩大指导，包括沿海危害，例如卡斯卡迪亚俯冲区和相关的海啸。这些演示将被杠杆化以形成永久性的展览和教学模块，这将极大地扩展这项外展工作。这项研究将提高我们对粉砂土壤的原地和实验室循环响应的理解，包括非线性，僵硬的降解，触发不稳定的多余孔压力以及相应的后果后的后果。具体而言，这项研究将：（1）缩小阈值罚款含量和可塑性，将“类似沙子”和“粘土状”的反应分开，对环状剪切应力/菌株的反应并识别关键的阈值；（2）比较过渡土壤的原位，单轴和双轴循环反应，以了解强层运动方向性的变化如何影响孔隙压力和体积应变的产生；（3）确定土壤织物，应力病史和饱和程度对过渡土壤的环状和循环后反应的影响；（4）将这项工作的区域发现与以前在过渡土壤上的努力联系起来；（5）通过长期寿命，协调的外展计划激发未来的地震学家，地质学家，地震工程师以及自然危害和弹性计划者。这项工作集中于针对小型至一大剪切菌株的实验，使用的技术范围从静坐周期性负载（从大型移动振动器和爆炸液化）到专门和协调的实验室测试，从而使前所未有的数据集的发展至关重要，以提高对内在和元素级别的响应的理解，再到构成元素的响应。