NEESR: Reduction of Seismic Shaking Intensity on Soft Soil Sites Using Stiff Ground Reinforcement

NEESR：利用刚性地基加固降低软土场地的地震震动强度

• 批准号: 1208117
• 负责人: Guney Olgun
• 金额: $ 92.55万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-10-01 至 2015-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1208117&HistoricalAwards=false
• 关键词: NEESR; Reduction; Seismic; Shaking; Intensity

The primary objective of this project is to develop a new seismic design concept for reinforced ground that can be used to reduce the intensity of strong ground shaking on soft sites. The study involves centrifuge and shake table testing as well as numerical modeling to demonstrate that stiff soil-mix panels, installed in lattice-type grids, can reduce the amplification of seismic energy up through soft soil profiles. In most cases, such ground reinforcement is used to increase bearing support, limit permanent deformations, and/or reduce liquefaction potential. Additional benefits, such as favorably altering the dynamic transfer function of the soil profile and thereby reducing the shaking levels input into the superstructure are not considered in current design provisions. Such reductions in ground shaking can lead to safer and more economical designs. This detailed study utilizes model testing with the centrifuge facility at the University of California Davis and a shake table at California State University Fullerton to demonstrate the effects of reinforcement geometry and layout, stiffness ratio, layering and properties of the soil profile, and other factors. Advanced three-dimensional nonlinear finite element modeling will be used to extrapolate the model test results to a wide range of field and site conditions so that design curves can be developed. This work represents an unprecedented approach to design ground improvement to reduce surface ground motions and base input into structures at seismically vulnerable soil sites. Data from this project will be archived and made available to the public through the NEES Project Warehouse/data repository (http://www.nees.org).The mitigation of the earthquake damage potential of soft soil sites remains one of the leading challenges in earthquake engineering. It is well-established through observations of earthquake damage patterns that structural damage is strongly correlated with local geological and soil conditions. Soft, weak sites generally fare worse than stiff sites. This is because soft sites tend to amplify the intensity of ground shaking and often undergo large deformations that can cause major structural damage. Earthquake damage potential can be significantly reduced by reinforcing and effectively stiffening such sites. Preliminary studies suggest that mixing cement with the soft soils to form stiff soil-cement panels in the ground (i.e., ?deep soil mixing?) can be an effective ground reinforcement technique for such purposes. Therefore soft soil sites can be transformed to behave like stiff sites, thereby greatly reducing earthquake vulnerability. The project is organized around an integrated plan of physical and analytical modeling to investigate and validate the effectiveness of various ground reinforcement techniques and develop a practical, economical design approach. This work has the potential to improve building performance, increase safety margins, and reduce development costs in earthquake prone regions. The findings will have implications not only for the engineering community, but also for business owners, developers, communities, and other stakeholders. As such, there is a well-developed plan for transferring knowledge into practice through partnership with the National Institute of Building Sciences (NIBS), the Deep Foundations Institute (DFI), and soil improvement contractors who are collaborating on this research. Results will be also be disseminated via conferences, journals, the project website, and incorporated into academic courses and professional shortcourses for groups such as American Society of Civil Engineers (ASCE), Federal Emergency Management Agency (FEMA), Federal Energy Regulatory Commission (FERC), and U.S. Army Corps of Engineers. There is also an aggressive outreach plan for the involvement of students from a predominantly undergraduate and minority serving institution, as well as from area K-12 schools. This award is part of the National Earthquake Hazard Reduction Program (NEHRP).

该项目的主要目标是开发一种新的加固地基抗震设计概念，可用于降低软土地基上强烈地面震动的强度。 该研究涉及离心和振动台测试以及数值模拟，以证明安装在网格型网格中的刚性土壤混合板可以减少通过软土剖面的地震能量放大。 在大多数情况下，这种地基加固用于增加轴承支撑、限制永久变形和/或降低液化可能性。 在当前的设计规定中，没有考虑额外的好处，例如有利地改变土壤剖面的动态传递函数，从而减少输入上部结构的震动水平。 这种地面震动的减少可以导致更安全和更经济的设计。 这项详细的研究利用加州戴维斯大学的离心机设施和加州州立大学富勒顿分校的振动台进行模型测试，以证明钢筋几何形状和布局、刚度比、分层和土壤剖面性质的影响，以及其他因素。 先进的三维非线性有限元建模将用于将模型试验结果外推到广泛的现场和现场条件，以便可以开发设计曲线。 这项工作代表了一个前所未有的方法来设计地面改善，以减少地面运动和基础输入到结构在地震脆弱的土壤网站。 该项目的数据将通过NEES项目仓库/数据库（http：//www.example.com）存档并向公众提供。减轻软土场地的地震破坏潜力仍然是地震工程的主要挑战之一。www.nees.org 通过对地震破坏模式的观察，人们已经确定，结构破坏与当地地质和土壤条件密切相关。软、弱的网站通常比硬网站更糟糕。 这是因为松软的场地往往会放大地面震动的强度，并且经常会发生可能导致重大结构破坏的大变形。 通过加强和有效加固这些场地，可以大大降低地震破坏的可能性。 初步研究表明，将水泥与软土混合，在地面上形成坚硬的水泥土面板（即，?深层土壤搅拌？）可以是用于这种目的的有效地基加固技术。 因此，软土场地可以转化为刚性场地，从而大大降低地震易损性。该项目围绕物理和分析建模的综合计划进行组织，以调查和验证各种地基加固技术的有效性，并开发实用，经济的设计方法。 这项工作有可能提高建筑性能，增加安全裕度，并降低地震多发地区的开发成本。 这些发现不仅对工程界有影响，而且对企业主、开发商、社区和其他利益相关者也有影响。因此，通过与国家建筑科学研究所（NIBS），深层地基研究所（DFI）和合作开展这项研究的土壤改良承包商合作，制定了一项将知识转化为实践的完善计划。 研究结果还将通过会议、期刊、项目网站进行传播，并纳入美国土木工程师协会（ASCE）、联邦应急管理局（FEMA）、联邦能源管理委员会（FERC）和美国陆军工程兵团等团体的学术课程和专业短期课程。还有一个积极的推广计划，让主要是本科生和少数民族服务机构的学生以及地区K-12学校的学生参与。该奖项是国家减少地震灾害计划（NEHRP）的一部分。