Preliminary Investigation and Implications of Improved Ground Performance during the 1999 Turkey Earthquakes

CMS 0085281标题：“1999年土耳其地震期间改进地面性能的初步调查和影响“PI：J. MartinInstitution：Virginia Polytechnic Institute and State UniversityAbstract：在世界各地，许多大城市都在低洼，相对平坦的海滨地区发展，这些地区的基础是河流，湖泊或海湾沉积的软弱，柔软的沉积物。就组成而言，这些沉积物通常含有软粘土和/或被高地下水位饱和的松散砂。特别令人关切的是，在这些地区建造的设施和生命线的安全性和完整性，以防止未来可能发生的大地震。如最近的大地震（加利福尼亚州旧金山弗朗西斯科、日本科比和土耳其伊斯坦布尔）所示，这些环境经常是土壤破坏（如过度沉降和大的横向移动）造成的严重基础设施损坏的地点。最近的经验表明，在这些环境中的潜在损害可以减少使用地面改良技术。因此，正在开发各种地基改造方法来加强和加固软弱土壤。这些技术包括压实、密实化、排水、置换、添加化学混合物以及其他措施，这些措施可以增加震动过程中对地面破坏的抵抗力。虽然这些技术被越来越多的人接受，但仍然缺乏性能数据来证实这些方法在实际地震荷载下的有效性（目前用于减轻地震破坏的土壤改良方法主要基于实验室和计算机研究）。 现场数据对于改进当前的设计程序和完善改进技术至关重要。在土耳其最近地震的受灾地区出现了一些改良土壤遗址，这为在实地条件下研究这些遗址提供了独特的机会。在1999年8月科贾埃利地震（M=7.4）和重大余震之后，PI在受影响地区进行了调查，以记录岩土现场性能。这些研究的重点是调查改良土壤的地点。确定了六个地点，并进行了实地勘察和初步分析。这些地点代表了一系列土壤条件和地面改良技术。 五个地点位于工业/商业环境中，含有松散砂和软粘土的混合物，采用振动密实、石柱和/或喷射灌浆进行处理。 其余的场地是一个由钢带和压实颗粒回填建造的加筋土墙。这些地点受到的地面运动范围约为0.10 g至0.35 g。初步观察结果显示，地基处理工程大致上能有效减轻地震造成的损害，特别是相对于附近未经处理的土地所造成的损害而言。 加筋土挡墙尽管承受了较大的地面位移，但也表现良好。 在勘察期间，对每个地点都进行了仔细研究和记录。虽然获得了大多数调查地点的一些底土数据和施工细节，但没有足够的数据来描述仔细详细研究所需规模的土壤条件。 特别令人关切的是，完全缺乏与主要研究地点相邻的未经处理的地点的岩土工程数据。未经处理的网站提供了一个重要的基础性能比较。提交本建议书是为了获得必要的数据，以便对这10个地点进行病例历史分析。 拟议的工作包括收集现有土壤数据（如有）、标准贯入试验（SPT）、圆锥贯入试验（CPT）、现场剪切波速度测量以及实验室指数和强度测试（在土耳其）。在这一阶段，工作的其余部分将用于对土耳其场址的初步案例分析。随后将提交一份提案，对改善的基础进行更全面的研究，其中将包括土耳其、台湾、日本和美国的案例，沿着数值模型和离心机数据。该项目将依赖于弗吉尼亚理工大学和土耳其研究人员之间的密切合作。 PI与Zetas工程公司和Bogazici大学的工程师和研究人员有着长期的密切关系。此外，弗吉尼亚理工大学和瑞士联邦理工学院最近成立了世界灾害风险管理研究所（DRM）。 瑞士政府、瑞士再保险和世界银行都支持DRM。 瑞士联邦理工学院、苏黎世（ETH）、弗吉尼亚理工大学、博阿齐奇大学和横滨国立大学最近通过DRM提出了一项合作建议，“减轻地震风险的小区划”。“该项目的瑞士部分由瑞士发展与合作署资助。目前正在与土耳其阿达帕扎里的Sakarya大学合作。目前的提案将在弗吉尼亚理工大学参与该项目中发挥不可或缺的作用。

CMS0085281Title: "Preliminary Investigation and Implications of Improved Ground Performance during the 1999 Turkey Earthquakes"PI: J. MartinInstitution: Virginia Polytechnic Institute and State UniversityAbstract:Across the world, many large cities have developed over low-lying, relatively flat waterfront areas underlain by weak, soft sediments deposited by rivers, lakes, or bays. In terms of make-up, these deposits typically contain soft clays and/or loose sands saturated by a high water table. Of particular concern is the safety and integrity of constructed facilities and lifelines in these areas against large earthquakes expected in the future. As illustrated by recent large earthquakes (San Francisco, CA; Kobe, Japan; and Istanbul, Turkey), these settings are frequently the site of heavy infrastructure damage from soil failures such as excessive settlement and large lateral movements. Recent experience indicates that damage potential in these environments can be reduced using ground improvement techniques. As a result, a variety of ground modification methods are being developed to strengthen and stiffen weak soils. These techniques involve compaction, densification, drainage, replacement, adding of chemical mixtures, and other measures that increase the resistance to ground failure during shaking. Although these techniques are seeing increased acceptance, there remains a lack of performance data to confirm the effectiveness of the methods under actual earthquake loadings (current soil improvement methods for earthquake damage mitigation are based primarily on laboratory and computer studies). Field data are crucial for improving current design procedures and refining improvement techniques. The presence of a number of improved soil sites in the affected region of the recent earthquakes in Turkey provides the unique opportunity to study such sites under field conditions. Following the August 1999 Kocaeli Earthquake (M=7.4) and significant aftershocks, the PIs performed investigations in the affected area to document geotechnical field performance. These studies focused on investigating improved soil sites. Six sites were identified, and field reconnaissance and preliminary analyses were conducted. The sites represented a range of soil conditions and ground improvement techniques. Five sites were located in industrial/commercial settings and contained mixtures of loose sands and soft clays that were treated using vibro-densification, stone columns, and/or jet grouting. The remaining site was a reinforced earth wall constructed of steel strips and compacted granular backfill. The sites were subjected to ground motions ranging from about 0.10g to 0.35g. The site locations ranged from 0 to 35 km from the zone of energy release.Preliminary observations showed that ground treatment was generally effective in mitigating earthquake-related damages, especially relative to damages observed at nearby sites of untreated ground. The reinforced earth wall also performed well despite being subjected to large ground displacements. Each site was carefully studied and documented during the reconnaissance. Although some subsoil data and construction details were obtained for most of the sites investigated, there were inadequate data to characterize soil conditions at the scale needed for careful, detailed study. Of particular concern is the complete lack of geotechnical data for untreated sites located adjacent to the main study sites. The untreated sites provide an important basis for performance comparisons. This proposal is submitted to obtain the data needed to make possible case history analysis of the ten sites. The proposed work involves collection of existing soil data where available, Standard Penetration Testing (SPT), Cone Penetration Testing (CPT), insitu shear wave velocity measurements, and laboratory index and strength testing (in Turkey). The balance of the effort during this phase will be directed toward preliminary case analysis of the Turkish sites. A subsequent proposal will be submitted to perform a more general study of improved ground that will include cases from Turkey, Taiwan, Japan, and the U.S., along with numerical modeling and centrifuge data.This project will rely on close collaboration between Virginia Tech and Turkish researchers. The PIs have a long-standing close relationship with engineers and researchers at Zetas Engineering Company and Bogazici University. Also, Virginia Tech and the Swiss Federal Institute of Technology recently established the World Institute for Disaster Risk Management (DRM). The Swiss government, Swiss Re, and the World Bank support DRM. The Swiss Federal Institute of Technology, Zurich (ETH), Virginia Tech, Bogazici University, and Yokohama National University through DRM recently developed a collaborative proposal, "Microzonation for Earthquake Risk Mitigation." The Swiss component of the project has been funded by the Swiss Agency for Development and Cooperation. Work with Sakarya University in Adapazari, Turkey is underway. The current proposal would play an integral role in Virginia Tech's involvement in this project.