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

摘要：在世界范围内，许多大城市都是在地势低洼、相对平坦的滨水地区发展起来的，这些滨水地区是由河流、湖泊或海湾沉积的软弱沉积物所覆盖的。就构成而言，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。特别值得关注的是这些地区建筑设施和生命线的安全性和完整性，以抵御未来可能发生的大地震。正如最近发生的大地震（加州旧金山、日本神户和土耳其伊斯坦布尔）所表明的那样，这些地区往往是土壤破坏（如过度沉降和大规模横向移动）导致基础设施严重受损的地点。最近的经验表明，使用地面改善技术可以减少这些环境中的潜在损害。因此，人们正在开发各种地基改造方法来加固和加固软弱土壤。这些技术包括压实、致密化、排水、更换、添加化学混合物和其他措施，以增加震动时地面破坏的抵抗力。虽然越来越多的人接受这些技术，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（目前减轻地震损害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改进技术至关重要。在土耳其最近发生地震的受影响地区存在一些改良的土壤地点，这为在实地条件下研究这些地点提供了独特的机会。在1999年8月Kocaeli地震（M=7.4）和重大余震之后，PIs在受灾地区进行了调查，以记录岩土领域的表现。这些研究的重点是调查改良的土壤地点。确定了六个场址，并进行了实地侦察和初步分析。这些地点代表了一系列的土壤条件和地面改善技术。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，使用振冲密实、石柱和/或喷射注浆进行处理。剩余的场地是由钢带和压实颗粒回填体构成的加筋土墙。这些地点受到约0.10g至0.35g的地面运动。这些地点距离能量释放区0至35公里。初步观测表明，地面处理在减轻地震相关损害方面总体上是有效的，特别是相对于在附近未经处理的地面观测到的损害而言。加筋土墙在较大的地面位移作用下也表现良好。在侦察期间，对每个地点都进行了仔细的研究和记录。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、详细研究所需的土壤条件。特别令人关切的是，主要研究地点附近未经处理的地点完全缺乏岩土工程数据。未经处理的站点为性能比较提供了重要的基础。提出这一建议是为了获得对这十个地点进行病例历史分析所需的数据。拟议的工作包括收集现有土壤数据（如有）、标准贯入测试（SPT）、锥贯入测试（CPT）、原位剪切波速测量以及实验室指数和强度测试（在土耳其）。这一阶段的剩余工作将用于对土耳其遗址进行初步个案分析。随后将提交一份提案，对改良地基进行更全面的研究，其中将包括来自土耳其、台湾、日本和美国的案例，以及数值模拟和离心机数据。这个项目将依靠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密切的关系。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、瑞士再保险公司和世界银行都支持DRM。瑞士联邦理工学院、苏黎世（ETH）、弗吉尼亚理工大学、Bogazici大学和横滨国立大学最近通过DRM开发了一项合作提案，“减轻地震风险的微分区”。该项目的瑞士部分由瑞士发展与合作署提供资金。与土耳其阿达帕扎里的萨卡里亚大学的合作正在进行中。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.