CSM/CNA UNO R&D Proposal Lee Petersen –CNA Consulting Engineers Mark Kuchta –Colorado School of Mines Requested budget: $200k/year for two years Cavern Design and Construction R&D

CSM/CNA UNO R&D Proposal With dimensions of 60m wide, 60m high, and 180m long, the proposed UNO excavation would be the largest underground civil structure ever constructed anywhere in the world. Before attempting such an ambitious project, it is imperative that a comprehensive research program be conducted regarding the design parameters, excavation procedure, support system, rock mass property requirements, and long-term stability issues that will be critical to the success of the UNO project.

Objective 1—Utilize Global Experience in Large Cavern Design and Construction at Great Depth 1. Conduct a comprehensive literature survey to include cavern size, cavern shape, site investigation, design methodology, construction methods, rock support and reinforcement, construction schedule, construction cost, and end use for similar large underground excavations that have been successfully completed (or attempted) throughout the world.

2. Convene a two-day workshop of academics, designers and constructors from around the world having fundamental knowledge or experience in the construction of large underground excavations. The purpose of the workshop will be primarily be to further develop the ideas discussed in task 1 as they relate to UNO construction. 3. Prepare a comprehensive technical report summarizing the results of the literature survey, design workshop, and identifying any critical topics requiring further research.

Objective 2—Define Rock Mass Characterization Issues for UNO 1.Investigate an document rock mass characterization and investigation methods that will be required for the proper design of the UNO cavern such a drilling, down-the-hole testing, remote sensing, horizontal and vertical stress determinations, etc. 2.Identify and investigate rock mass scale issues involved in scaling up from existing cavern sizes to the dimensions required for UNO. 3.Investigate the requirements for initial pilot excavations.

Objective 3—Identify Design Methodologies for UNO 1.Extend empirical design methods developed in objective 1 to UNO size and depth. 2.Investigate limitations (if any) of analytical methods for large cavern design using numerical modeling software such as the Universal Distinct Element Code (UDEC) and the Fast Lagrangian Analyses of Continua (FLAC) numerical codes.

Objective 4—Investigate Design and Construction Issues for UNO 1.Using analytical methods, analyze the stress concentrations and excavation stability as a function of the shape of the final excavation. It is possible that a large elliptical shaped excavation would be more stable at depth that a shoebox shaped cavern.

2. Develop three different strategies for the excavation of the UNO cavern. Using numerical methods, analyze the stress concentrations and excavation stability at various stages of the excavations in order to identify a preferred excavation sequence that will maximize overall stability during excavation, and minimize the potential undesired stability problems such as rock bursts. 3. Identify any significant limitations of materials, equipment, methods and personnel for each of the three excavation strategies.

Rock burst at the Gotthard Tunnel

Objective 5—Prepare Conceptual Design for UNO 1.Prepare Generic Site Description, including Rock Mass Characteristics, and Reasonable Ranges for Key Parameters 2.Prepare Conceptual Design Based on Empirical Design Methods 3.Prepare Conceptual Design Based on Modeling Methods 4.Investigate Influence of Depth, In Situ Stresses, Rock Mass Strength, Discontinuity Spacing, Cavern Shape 5.Investigate Outfitting Issues, Including Water Containment, Bulkheads

Objective 6—In-Service Performance 1.Interaction between Internal Structures, Water Containment Membranes and Ongoing Rock Movement 2.Design and Operation Requirements for Filling and Emptying the Cavern 3.Service Life Issues (Materials, Corrosion, Long-Term Rock Behavior)

Objective 7—Risk Management Strategies 1.Site Investigation, Site Selection, Design, Procurement, Construction, Operation

Results 1.The results of these investigations will be made available through a series of technical reports, and 2.through various documents to be made available through a dedicated UNO web page.