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, szlatanic@hntb.com,
Patrick H.C. Chan, P.E., (M.ASCE), Senior Supervising Structural Engineer, Professional Associate, Parsons Brinckerhoff, One Penn Plaza, New York, NY 10119, USA, ChanP@pbworld.com,



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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