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Appendix D Geotechnical Design Reports, Rock Tunnels and Earth Tunnels The Designer shall prepare Geotechnical design reports for each rock and/ or earth tunneling construction contract. The reports are to provide the Authority, the Authority's General Consultants, and the Board of En- gineering Consultants with the Geotechnical basis of the design and of the construction specifications for their assessment of the recommended design. Further, the reports will be issued to bidders, will become part of the Construction Contract Documents, and will be reference information for the Engineer acting for the Authority during con- struction. It is intended that the reports will be based on and present the most current subsurface information pertaining to the Design Section and each particular construction contract. On that account, where appli- cable, the reports are to be prepared in successive stages as follows: Stage 1, for presentation to the General Engineering Consultant at the preliminary review stage of design. The Designer's Geotechnical Design Report is to describe the basis of their design and the provisions to be made in the de- sign and specifications for the geological conditions. Con- siderations with respect to requirements for additional sub- surface investigations and proposals regarding other major design and construction aspects are to be included. Stage 2, for presentation to the General Engineering Consultant at the final review stage of design. This will be an update of Stage l and will incorporate further information developed or obtained up to that time. The update will reflect, among other things, comments made at the prelim- inary presentation, the newest information from GSC (General Soils Consultant) subsurface investigations, and applicable data from experience on other Authority construction projects. (For rock tunnel stations, the data may include detailed geo- logic mapping of shafts, pilot tunnels, and running tunnels carried out in the area by the General Construction Consultant during the course of the preceding tunnel contract.) *In the formal terminology of WMATA "Washington Metropolitan Area Tran- sit Authority), the "Geotechnical Basis of Design and Construction Spec- ifications." 149

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The report shall conform to the Geotechnical Design Report format furnished to the Designer by the Authority. The completed report is to reflect the comments made at the final review presentation and is to be printed as an appendix to the construction specifications. 150

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FORMAT FOR ROCK TUNNELS GEOTECHNICAL DESIGN REPORT A. TITLE Geotechnical Basis of Design and Construction Specifications. B . INTRODUCT ION This report describes geological conditions anticipated along the route of Section tunnels of the Route of the Washington Metropolitan Area Transit System, and the influence these anticipated geological conditions have had upon the design. In addition, the report is intended to assist prospective bidders in evaluating the requirements for supporting the tunnel; to enable the Contractor to plan his work; and to assist the Engineer in reviewing Contractor's submittals and operations. Add a general, one-paragraph description of the project. C . SOURCES OF IN FORMAT ION Subsurface investigation reports by GSC (General Soils Consultant). Construction experience reports by GCC (General Construction Consultant). Geologic reports by other agencies or individuals. Technical publications. D. GEOLOGIC SETTING Regional geology: discussion, geologic map, and generalized cross section of Washington, D.C., area. Site exploration: description of subsurface investigations that have been carr fed out. Site geology: geologic profile along the tunnel route with discussions of physiography, stratigraphy, and structure. E. GEOLOGIC FEATURES OF ENGINEERING SIGNIFICANCE Lithology ( rock types) Weathering profile Joints, foliation, bedding Shear zones and faults Rock hardness and drillability Groundwater. F. SELECTION OF TUNNEL SUPPORT Definitions: initial support, permanent lining. Types of initial support considered, such as: Steel ribs Shotcrete Rock bolts. Types of permanent lining considered, such as: Cast-in-place reinforced concrete lining Rock bolts Shotcrete Steel ribs and shotcrete composite. 151

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DESIGN OF TUNNEL SUPPORT Initial support: Contractor designed Minimum requirements Early installation. Permanent lining: Loading conditions Basis of stress analysi- Design thickness. H. ANTICIPATED CONSTRUCTION PROBLEMS, GROUND BEHAVIOR Geological reasons. Potential effects on: Tunnels and pillars Shafts Portals Double crossovers Stations and entrance excavations Solutions: TBM design Excavation sequences Blasting requirements Early initial support Grouting Groundwater control Instrumentation , _ I. CONSTRUCTION SPECIFICATIONS Discussion of the reasons for important or unusual requirements. 152

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FORMAT FOR EARTH TUNNELS GEOTECHNICAL DESIGN REPORT A. TITLE Geotechnical Basis of Design and Construction Specifications. B . INTRODUCT ION This report describes geological conditions anticipated along the route of Section tunnels of the Route of the Washington Metropolitan Area Transit System, and the influence these anticipated geological conditions have had upon the design. In addition, the report is intended to assist prospective bidders in evaluating the requirements for supporting the tunnel; to enable the Contractor to plan his work; and to assist the Engineer in reviewing Contractor's submittals and operations. Add a general, one-paragraph description of the project. C. SOURCES OF INFORMATION Subsurface investigation reports by GSC (General Soils Consultant). Cons truc t ion experience reports by GCC (Gene ral Cons tr uction Consultant). Geological reports by other agencies or individuals. Technical publications. D. GEOLOGIC SETTING Regional geology: discussion, geologic map, and generalized cross section of Washington, D.C., area. Site exploration: description of subsurface investigations that have been carried out. Site geology: geologic profile along the tunnel route with discussions of physiography, stratigraphy, and structure. E . GEOLOG IC FEATURES OF ENGI NEERI NG S I ON I F ICANCE Bedrock, weathering profile (if it impinges on tunnel). Engineering properties of: Strata of the Cretaceous Age Potomac Formation Strata of the Pleistocene river terrace deposits Recent alluvium Fill Groundwater Present streams and old stream channels. F. . SELECT ION OF TUNNEL SUPPORT Definitions: initial support, permanent lining. Types of initial support considered, such as: Steel ribs and lagging Metallic plate liner Types of permanent lining considered, such as: Cast-in-place reinforced concrete lining Fabricated gray iron segmented lining Fabricated ductile iron segmented lining 153

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- . Fabricated steel segmented lining Precast concrete lining. G. DESI GN OF TUNNEL SUPPORT Initial support: Expansion of steel ribs Grouting tail skin void Grouting voids behind lining Construction and short-term loadings Permanent lining: Loading conditions Basis of stress analysis Design thickness ~ H. ANTICIPATED CONSTRUCTION PROBLEMS, GROUND BEHAVIOR Geological reasons. Potential effects One Streets Utilities Buildings Solutions: Shield design Tunneling sequences General construction procedures Underpinning Grouting Groundwater control Instrumentation. I. CONSTRUCTION SPECIFICATIONS Discussion of the reasons for important or unusual requirements. 154