Deformation Based Design Methodology for Excavation Support Systems

基于变形的开挖支护系统设计方法

• 批准号: 0650911
• 负责人: Lindsey Bryson
• 金额: $ 7.85万
• 依托单位: University of Kentucky Research Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-10-01 至 2009-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0650911&HistoricalAwards=false
• 关键词: Deformation; Based; Design; Methodology; Excavation

Abstract:Underground construction and rehabilitation projects are prevalent in many urban areas across the country. Space for construction activities is usually limited at these project sites because of the close proximity of adjacent infrastructure. A major concern for projects involving deep excavations is the impact of excavation-related ground movements on adjacent buildings and utilities. Excessive lateral movements at the edge of the excavated area can lead to significant displacements and rotations in adjacent structures. Consequently, control of lateral displacements is a major design consideration for excavation support systems. In many urban areas, the project site is underlain by soft clays. This requires additional considerations because of the contributions from consolidation and creep of the soil. Strict deformation control is often required to minimize damage to adjacent structures for many urban projects. Control of deformations is typically achieved with stiff excavation support systems. Traditionally, excavation support systems are designed using apparent earth pressure diagrams. Using this approach, the support system design becomes a function of the maximum anticipated earth pressure and is governed by overall structural stability as opposed to maximum allowable horizontal or vertical deformation. This approach produces a support system that is adequate with regard to preventing structural failure, but may result in excessive wall deformations and ground movements. Existing methods that do consider deformations relate lateral wall movements to excavation support system stiffness and basal stability. However, these were developed using a limited number of wall types and configurations, and do not include considerations for differing materials of an excavation support system; the three-dimensional effects of the wall construction; the effects of different support types; the influences of the excavation geometry and sequencing; or complex site geology. Due to the complexity of the excavation support system and the excavation process, it is easily concluded that for a realistic analysis of the interaction between the soil and the excavation support system, a three-dimensional finite element model is required. The intellectual merit of this research is that the most recent studies have shown that excavation-induced ground movements and the complicated soil-structure interactions of the excavation support system are three-dimensional in nature. However, to date limited data has been reported in the literature that presents a fully three-dimensional finite element analysis of a deep excavation. In addition, no one has presented a design methodology for excavation support systems that incorporate the three-dimensional influences of constructing the support wall and installing the support system; the three-dimensional influences of excavating and backfilling the site (including time delays for infrastructure construction); and the influences of three-dimensional ground deformations. This research will provide the three-dimensional finite element analysis of three case histories and will develop a deformation-based design methodology. The broader impact of this research is that a deformation-based designed methodology will potentially save millions of dollars typically expended for repairs and mitigation of excavation-induced damage to adjacent infrastructure. In addition, the results of this research will directly and indirectly be applicable to tunnel design, design of earth retaining walls, cofferdam design, and deep foundations design (eg. drilled shafts, auger-cast piles, cassions, etc.). It is also envisioned that these research results will be extended to evaluating structure response to ground movements resulting from construction activities such pipe jacking and construction dewatering. Another logical extension of this research is evaluating the building and utility response to dynamic loading-induced ground movements such as blast loads, construction vibrations, and earthquake loading. This research will also facilitate participation of undergraduate researchers, with special emphasis on participation of underrepresented groups.

翻译后摘要：地下建筑和修复工程在全国许多城市地区普遍存在。 由于邻近基础设施的距离很近，这些项目工地的建筑活动空间通常有限。 涉及深开挖的项目的一个主要问题是与开挖有关的地面运动对邻近建筑物和公用设施的影响。 开挖区域边缘的过度横向移动会导致相邻结构的显著位移和旋转。 因此，控制侧向位移是开挖支护系统的主要设计考虑因素。 在许多城市地区，项目场地下面是软粘土。 这需要额外的考虑，因为来自土壤的固结和蠕变的贡献。 在许多城市工程中，为了尽量减少对邻近结构的破坏，往往需要进行严格的变形控制。 变形的控制通常通过刚性挖掘支撑系统来实现。 传统上，开挖支护系统的设计使用表观土压力图。 使用这种方法，支撑系统设计成为最大预期土压力的函数，并受整体结构稳定性的控制，而不是最大允许水平或垂直变形。 这种方法产生的支撑系统足以防止结构破坏，但可能导致过度的墙体变形和地面移动。 考虑变形的现有方法将侧壁移动与开挖支撑系统刚度和基底稳定性联系起来。 然而，这些是使用有限数量的墙类型和配置开发的，并且不包括对挖掘支撑系统的不同材料的考虑;墙结构的三维效果;不同支撑类型的效果;挖掘几何形状和顺序的影响;或复杂的现场地质。 由于开挖支护系统和开挖过程的复杂性，很容易得出结论，为了真实分析土壤和开挖支护系统之间的相互作用，需要三维有限元模型。 这项研究的智力价值是，最新的研究表明，挖掘引起的地面运动和复杂的土-结构相互作用的挖掘支撑系统是三维的性质。 然而，到目前为止，有限的数据已在文献中报道，提出了一个完整的三维有限元分析的深基坑。 此外，还没有人提出一种用于开挖支撑系统的设计方法，该设计方法包括建造支撑墙和安装支撑系统的三维影响;开挖和加固现场的三维影响（包括基础设施建设的时间延迟）;以及三维地面变形的影响。 本研究将提供三个案例的三维有限元分析，并将开发一个基于变形的设计方法。 这项研究的更广泛的影响是，基于变形的设计方法可能会节省数百万美元，通常用于维修和减轻挖掘引起的对邻近基础设施的损害。 此外，本文的研究成果将直接或间接地应用于隧道设计、挡土墙设计、围堰设计和深基础设计（如：钻孔竖井、螺旋灌注桩、套管等）。 还可以设想，这些研究成果将扩展到评估结构对施工活动（如顶管和施工降水）引起的地面运动的响应。 本研究的另一个逻辑延伸是评估建筑物和公用设施对动态荷载引起的地面运动（如爆炸荷载、建筑振动和地震荷载）的响应。 这项研究还将促进本科研究人员的参与，特别强调代表性不足的群体的参与。