Automated sensing and three-dimensional analysis of internally braced excavations.

摘要

Design of deep supported excavations in urban environments requires an accurate prediction of soil, support system, and adjacent structure response to construction activities. Current empirical and numerical design methods are limited by soil parameter determination, due to soil variability and disturbance effects, and geometric simplifications. Observational and inverse analysis methods have been developed for deep excavation analysis to allow adaptation of excavation support design based on support system performance at early stages of construction. Manual collection and processing of the performance monitoring data, required for adaptive design methods, is often too time consuming for successful implementation of these methods. However, development of automated, remote-access geotechnical and structural instrumentation techniques allow timely data transfer and successful implementation of adaptive design methods.; In addition to soil parameter variability, finite element methods for excavation support design are often limited by simplifications of construction procedures and geometry to allow for two-dimensional (2D) plane-strain analysis. A number of case histories and numerical analyses have demonstrated that deep excavation geometry is greatly influenced by excavation sequence and three-dimensional (3D) corner restraining effects.; A combination of developing and traditional geotechnical and structural monitoring instrumentation was implemented on the Ford Engineering Design Center (FEDC) excavation site, on the Northwestern University campus, in Evanston, Illinois. This dissertation describes development and deployment of an automated, remote-access optical survey station and remote-access tiltmeters which allowed for monitoring and analysis of soil and structure response to the FEDC excavation in 'real-time'. A method of determining thermal and earth loading of internal bracing members from 'real-time' strain gage observations is developed and proposed herein.; This dissertation also investigated the influence of excavation sequence and three-dimensional geometry on finite element calculation of soil and support system response to deep excavations. FEDC slope inclinometer and internal bracing load data were compared to soil and support responses calculated with 3D finite element models to demonstrate the influence of excavation sequence on soil and support system response. Lastly, a 3D finite element parametric analysis was conducted and is described herein, which illustrates influence of soil stratigraphy, support system stiffness and excavation geometry on the three-dimensional restraining effects.