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OCR for page 149
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."
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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.
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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.
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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.
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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
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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
Representative terms from entire chapter:
steel ribs
