Advancing the Capabilities of Adaptive Management Techniques in Geotechnics

自适应管理技术提供了一种手段，将传感器开发、信息技术和数值分析的进步结合到岩土工程中的各种问题上。如果一个人想要预测并随后评估设计的整体性能，观察法？Peck支持的是一个众所周知的框架，其中施工和设计程序和细节根据施工过程中的观察和测量进行调整。适应性管理技术使人们能够自动化观察方法，以便能够以足够及时的方式将量化信息分发给感兴趣的股东，以便在许多应用中使用。这种方法在将民用基础设施扩展到地下环境时有特别的应用。人口密度的增加，以及基础设施投资、国土安全、能源保护和可持续设计的新需求，将要求我们在更高效、更安全地创造地下空间的能力方面取得重大进展。影响开挖引起的地表移动的因素很多，包括地层、土壤性质、支撑系统细节、施工活动、合同安排和施工工艺。虽然在设计过程中分析开挖对地面的响应时，数值模拟已经变得越来越常见，但有限元预测包含与土壤属性、支撑系统细节和施工程序相关的不确定性。在将适应性管理方法应用于问题时，明确考虑了这些因素，尽管该方法有其随后讨论的局限性。在许多地方，监管机构或通过认识到过度地面移动的不利影响，对与深挖有关的允许地面移动施加了更严格的限制。一些城市地区的挖掘活动受到的限制甚至比5年前要小得多。例如，在西雅图地区，开挖引起的地面移动被限制在1英寸以下，深度为70英尺。芝加哥的挖掘要求现在的目标是最大地面移动1-1/2到2英寸，而十多年前只有4英寸。在芝加哥，这些问题变得更加复杂，因为现在正在进行的挖掘深度为75英尺，比通常的40英尺深得多。波士顿地区的许多挖掘活动仅限于1英寸的地面移动。鉴于波士顿和芝加哥的地下条件由相对较软的粘土组成，这些要求对开挖支撑设计和施工提出了挑战。因此，预测地面变形的最新技术已经达到了一个点，当移动被限制在如此小的量时，需要在实践中取得重大进展才能做出准确的设计评估。这些进展也需要使适应性管理方法适用于这些类型的问题。这项研究的目的是将适应性管理方法扩展到一系列必须限制地面变形以防止对邻近建筑物和其他基础设施造成损害的问题。特别是，提出了土的小应变非线性、墙体的非线性刚度和楼板的收缩对开挖变形的相对影响。这项研究将包括从芝加哥和波士顿的开挖中切割的块状样品的实验室试验，以表征土体的本构行为，重点是小应变响应，在深基坑中测量地面变形和支撑系统的结构响应并与现场施工活动相关的详细现场试验，以及基于现场观测的反分析的有限元模拟和事后适应性管理评估。

Adaptive management techniques provide a means to incorporate advances in sensor development, information technology, and numerical analyses to a variety of problems in geotechnical engineering. If one wants to predict and subsequently evaluate the overall performance of a design, the ?observational method? espoused by Peck is a well-known framework wherein construction and design procedures and details are adjusted based upon observations and measurements made as construction proceeds. Adaptive management techniques allow one to automate the observational approach so that quantitative information can be distributed to interested shareholders in a timely enough fashion to be of use in a number of applications. This methodology has particular application when extending civil infrastructure into the subsurface environment. The increase in population density, as well as new imperatives for infrastructure investment, homeland security, energy conservation and sustainable design, will require major advances in our ability to create underground space more efficiently and safely. Many factors affect the ground movements caused by excavations, including stratigraphy, soil properties, support system details, construction activities, contractual arrangements and workmanship. While numerical simulations have become more common when analyzing ground response to excavations as part of the design process, finite element predictions contain uncertainties related to soil properties, support system details, and construction procedures. These factors are explicitly considered when applying adaptive management methods to the problem, although the methodology has its limitations as subsequently discussed. Stricter limits on allowable ground movements associated with deep excavations are being imposed in many locales by either regulatory agencies or by recognition of adverse effects of excessive ground movements. Excavations in some urban areas are being subjected to movement limitations that are much smaller than even just 5 years ago. For example, excavation-induced ground movements in the Seattle area are limited to 1 inch for cuts at deep as 70 ft. Requirements for excavations in Chicago are now targeted for maximum ground movements of 1-1/2 to 2 inches, down from 4 inches just over a decade ago. These issues are compounded in Chicago by the fact that excavations now are being made to depths of 75 ft, much deeper than the typical depth of 40 ft. Many excavations in the Boston area are limited to 1 inch of ground movement. Given that the subsurface conditions at Boston and Chicago consist of relatively soft clays, these requirements present a challenge in excavation support design and construction. Consequently, the state-of-the-art of predicting ground deformations has reached a point where major advances in practice are required to make accurate design assessments when movements are limited to such small amounts. These advances also are needed to make the adaptive management approach applicable to these types of problems.The purpose of this research is to extend the adaptive management approach so that it applies to a range of problems where ground deformations must be limited to prevent damage to adjacent buildings and other infrastructure. In particular it is proposed to quantify the relative effects of small strain non-linearity of soils, non-linear stiffness of walls and shrinkage of floor slabs used in top-down construction on the deformations associated with excavations. This research will include laboratory experiments on block samples cut from excavations in Chicago and Boston to characterize the constitutive behavior of the soils with emphasis on the small strain responses, detailed field experiments at deep excavations where ground deformation and structural responses of the support system are measured and related to the construction activities at the site, and finite element simulations and after-the-fact adaptive management evaluations using inverse analysis based on observed field observations.