Interpretation of Centrifuge Test Results of the Seismic Response of Temporary Braced Excavations near Tall Buildings

Jones, Christina Louise

Graduate Thesis Or Dissertation

Interpretation of Centrifuge Test Results of the Seismic Response of Temporary Braced Excavations near Tall Buildings Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/dz010q40s

Abstract

Underground structures such as cut-and-cover box structures and retaining wall systems have performed relatively well during past seismic events. However, notable cases such as the failure of the Daikai Subway Station during the 1994 Kobe Earthquake show the importance of the seismic design of these types of structures. Braced excavations are a type of underground structure used to provide space for the construction of cut-and-cover tunnels, basements, foundations, and other permanent underground structures. Even though temporary, braced excavations need to be designed to withstand seismic loads. Current seismic design of underground structures assumes the case of isolation with no adjacent buildings. In reality, underground structures such as braced excavations and subway systems are located in densely populated downtown areas, with adjacent buildings. This research aims to provide insight into the seismic response of braced excavations near tall buildings.Data from three dynamic centrifuge tests were analyzed to evaluate soil-structure-underground structure-interaction (SSUSI) near a temporary braced excavation. Dry, medium dense, Nevada sand was used as the test soil. The first test studied the braced excavation in isolation with no adjacent buildings. The second and third tests studied the same excavation with an adjacent midrise and highrise building, respectively. Various methods of measuring small-strain soil properties in the far-field are explored in this thesis and compared. The seismic response of the braced excavation are presented during the three centrifuge tests in terms of racking displacements, dynamic lateral earth pressures, and bending moments along the excavation walls as well as axial forces on struts to evaluate the seismic impact of an adjacent tall building on the performance of a braced excavation. The conclusions and observations presented in this thesis are preliminary and based on experimental results alone. Final, generalized design recommendations cannot be drawn from these observations. Results from numerical simulations currently being performed by the University of Illinois-Urbana under the direction of Professor Hashash will be used in addition to these experimental results to provide design recommendations in the future.

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