Design of Large-Span Caverns in Rock under Shallow Cover

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by Sanja Zlatanic, P.E., (M.ASCE), Vice President; Chief Tunneling Engineer, HNTB, Five Penn Plaza, New York, NY 10001, USA,,
Patrick H.C. Chan, P.E., (M.ASCE), Senior Supervising Structural Engineer, Professional Associate, Parsons Brinckerhoff, One Penn Plaza, New York, NY 10119, USA,,

Document Type: Proceeding Paper

Part of: GeoCongress 2012: State of the Art and Practice in Geotechnical Engineering

Abstract: Amid lack of a national code for tunnel design, this paper presents a comprehensive and systematic approach in designing large-span caverns in rock under shallow cover beneath dense urban environment. Important considerations including issues concerning fire protection and water-tightness of major underground structures are addressed. Structural design criteria encompassing the rationale in determining structural `loads', load factors, load combinations, Capacity/Demand (C/D) ratios and serviceability check are presented and explained via flowchart. A practical and efficient design of the cavern liner and interior structures for major openings excavated in rock requires implementation of practical choices for numerical analyses and design; hence, a most efficient use of two-dimensional and three-dimensional continuum/discontinuum analyses in combination with structural analyses incorporating ground-structure interaction is described. These analyses include considerations of impacts from the future high-rise overbuild on these large openings excavated in rock under relatively shallow cover. An example is presented illustrating procedures to determine configuration of overbuild `load plates', formed to reflect a major future development, and to incorporate the resulting forces in design of the large underground structures. Design and analytical complexities arising from cavern/tunnel intersections are also addressed. Similar design and analytical methodology has been implemented successfully on major works in New York metropolitan area.

Subject Headings: Rocks | Load factors | Tunnels | Three-dimensional analysis | Two-dimensional analysis | Underground structures | Load combinations | North America | United States | New York

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