SGER: Geotechnical Site Characterization for Instrumented Excavation Sites

SGER：仪表挖掘场地的岩土工程特征

• 批准号: 0338445
• 负责人: Paul Mayne
• 金额: $ 3.89万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-01 至 2005-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0338445&HistoricalAwards=false
• 关键词: SGER; Geotechnical; Site; Characterization; Instrumented

In this SGER, a geotechnical site characterization program will be performed by Georgia Tech (GT) using in-situ seismic piezocone (SCPTu) and seismic flat plate dilatometer tests (SDMT) to capture the geostratigraphy, soil properties, and small-strain stiffness at three sites. Two sites involve specially-instrumented large excavations at the Ford Design Center on the Northwestern University campus and the Prentice Women's Hospital in downtown Chicago. The third site is the National Geotechnical Experimentation Site (NGES) on the western shore of Lake Michigan. These projects are selected in collaboration with a joint NSF project by Northwestern University (NU) and the University of Illinois at Urbana-Champaign (UIUC) to develop new integrated tools to predict, monitor and control ground movements associated with construction of supported excavations. Since September 2002, the NU-UIUC activities have focused on collecting and analyzing detailed field performance data at several excavations in the Chicago area, developing and evaluating new methods to track excavation progress, and developing numerical techniques to automatically update predictions of performance of the excavation support system. Block and piston samples have been collected for laboratory testing using internally-mounted local strain sensors to capture the nonlinear stress-strain-strength behavior of the soft clay soils. Of particular merit is the inclusion of the small-strain shear modulus (Gmax = G0) in the numerical scheme as a key initial state parameter in order to realistically model the induced strains and stresses within the soil mass surrounding the excavations. Current available commercial packages (e.g., PLAXIS, CRISP, FLAC, SV-Solid) do not include any built-in algorithms to start the constitutive nonlinear stress-strain-strength curves of the soil regions from the initial fundamental G0 stiffness. Yet, natural soil deposits and formations all originate from an initial state condition specified by their in-place void ratio (e0), vertical stress (svo), hydrostatic porewater pressure (uo), lateral stress coefficient (K0), and small-strain stiffness (G0 = rT Vs2). While laboratory tests such as resonant column and bender elements can provide evaluations of G0, only discrete values are obtained and sample disturbance issues often arise. Therefore, in-situ soil parameters and properties are desired, particularly using geophysical tests via the planned sets of SCPTu and SDMT soundings and derived shear wave velocity profiles. Since the Evanston NGES is located nearby, the GT team will calibrate their new true-interval downhole seismic array in a SDMT deployment with standardized test data already available and documented at the NGES. At each of the three test sites, a series of 3 to 6 SCPTu and SDMT soundings will be performed to optimize data field collection. Based on prior information, the sites are underlain by sand and/or fill overlying soft clayey silts, stiffer clays, and tills (Finno, 1989 GSP 23; 2000, GSP 93). At select soundings, detailed shear wave profiles can be obtained by frequent true-interval surveys. Working with Professor Rich Finno of NU and Professor Yousef Hashash of UIUC, the interpretation of relevant parameters ?e.g., g??f', su, OCR, K0, E', Eu) will be evaluated for input into the numerical modeling. In terms of Intellectual Merit, the intended goals involve the optimized collection of site-specific data using hybrid tests (SCPTu and SDMT) which combine penetration type probes with geophysical methods to ascertain multiple measurements in a single sounding. In-situ shear wave profiles will allow the utilization of small-strain stiffness for the initial portion of the stress-strain-strength curves of soil layers within the updated FEM algorithms by NU-UIUC. In terms of Broader Impacts, this SGER seeks to establish a collaborative effort between NU-UIUC-GT on a major initiative towards a fully-integrated system of laboratory and in-situ testing, numerical finite element simulation, and continued feedback from embedded-wireless field sensors within the controlled excavations during construction. The utilization of small-strain stiffness is paramount to reflecting the true anticipated response of the construction operations. The complementary nature of the laboratory testing and cone/dilatometer/shear wave testing in calibration with full-scale field performance of walls and supports during excavation and detailed modeling can benefit future urban projects and infrastructure redevelopments in the US. Finlaly, during field visits to the NU and UIUC campuses, the GT team will offer demonstrations of in-situ techniques to graduate students and interested parties.

在本SGER中，格鲁吉亚技术公司（GT）将使用现场地震压锥（SCPTU）和地震平板应变仪测试（SDMT）执行岩土工程场地表征计划，以获取三个场地的地质地层、土壤特性和小应变刚度。两个地点涉及在西北大学校园的福特设计中心和芝加哥市中心的普伦蒂斯妇女医院进行的特殊仪器大型挖掘。第三个地点是位于密歇根湖西岸海岸的国家岩土工程试验场。 这些项目是与西北大学（NU）和伊利诺伊大学厄巴纳-香槟分校（UIUC）的NSF联合项目合作选择的，以开发新的集成工具来预测，监测和控制与支持挖掘施工相关的地面运动。自2002年9月以来，NU-UIUC活动的重点是收集和分析详细的现场性能数据在几个挖掘在芝加哥地区，开发和评估新的方法来跟踪挖掘进度，并开发数值技术，自动更新的挖掘支撑系统的性能预测。 已收集的块和活塞样品进行实验室测试，使用内部安装的局部应变传感器，以捕捉非线性应力-应变-强度特性的软粘土。特别值得一提的是，在数值方案中将小应变剪切模量（Gmax = G 0）作为一个关键的初始状态参数，以便真实地模拟开挖周围土体中的诱导应变和应力。当前可用的商业软件包（例如，PLAXIS、CRISP、FLAC、SV-Solid）不包括任何内置算法，以从初始基本G 0刚度开始计算土壤区域的本构非线性应力-应变-强度曲线。然而，天然土壤沉积物和地层都起源于由其就地孔隙比（e0）、垂直应力（svo）、静水孔隙水压力（uo）、侧向应力系数（K 0）和小应变刚度（G 0 = rT Vs 2）指定的初始状态条件。虽然共振柱和弯曲元件等实验室测试可以提供G 0的评估，但只能获得离散值，并且经常出现样品干扰问题。因此，需要现场土壤参数和特性，特别是通过计划的SCPTU和SDMT探测集和导出的剪切波速度剖面进行地球物理测试。 由于埃文斯顿NGES位于附近，GT团队将校准他们的新的真间隔井下地震阵列在SDMT部署与标准化的测试数据已经提供和记录在NGES。在三个试验地点的每一个，将进行一系列3至6次SCPTU和SDMT探测，以优化数据现场收集。 根据先前的信息，这些场地下面是砂和/或填料，覆盖在软粘土质粉土、硬粘土和冰碛上（Finno，1989 GSP 23; 2000，GSP 93）。 在选定的水深处，可以通过频繁的真间隔测量获得详细的剪切波剖面。 与NU的Rich Finno教授和UIUC的Yousef Hashash教授合作，解释相关参数？例如，在一个实施方式中，g？？f '，su，OCR，K 0，E'，Eu）将被评估以输入到数值建模中。 在智力价值方面，预期目标涉及使用混合测试（SCPTU和SDMT）优化特定场地数据的收集，混合测试将联合收割机穿透型探头与地球物理方法结合起来，以确定在一次测深中的多个测量值。原位剪切波剖面将允许利用NU-UIUC更新的FEM算法中土层应力-应变-强度曲线的初始部分的小应变刚度。 在更广泛的影响方面，该SGER旨在建立NU-UIUC-GT之间的合作努力，主要致力于建立一个完全集成的系统，包括实验室和现场测试，数值有限元模拟，以及施工期间受控开挖中嵌入式无线现场传感器的持续反馈。 小应变刚度的利用对于反映施工操作的真实预期响应至关重要。在挖掘和详细建模期间，实验室测试和锥形/波速计/剪切波测试与墙和支撑的全尺寸现场性能校准的互补性可以使美国未来的城市项目和基础设施重建受益。最后，在对NU和UIUC校园的实地考察期间，GT团队将为研究生和感兴趣的各方提供现场技术演示。