Underground

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Underground
National Energy Supergrid Workshop November 7,
2002 Palo Alto
Edward J. Cording University of Illinois at
Urbana-Champaign
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Underground
National Energy Supergrid Workshop November 7,
2002 Palo Alto
Edward J. Cording University of Illinois at
Urbana-Champaign
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Scale 6 inches to 200 feet

• Rock Chambers 60 to 100 ft wide
• Rock tunnel boring machines (TBMs) with disk
  cutters
• 8 to 40 ft diameter
• Most economic 10 to 15 ft diameter, gt 5000 ft
  length
• Soil tunnel shields with pressurized chambers to
  support face
• Micro Tunneling jacking a pipe, removing muck
  by slurry line
• less than 3 ft dia is no-entry, larger diameters
  can be entered.
• Length determined by jacking forces tunnel
  lengths greater than 1000 can be driven using
  intermediate jacking stations inserted in the
  pipe string.
• Horizontal Directional Drilling
• typical 300 to 1500 ft long, 6 to 24 in.
  diameter
• up to 48 and 3000 length, up to 24 and 6000
  length.
• Open Excavation
• Large braced excavations and shafts
• Trenching
• Trenchers and Excavators
• Rock chain driven cutters with rock picks, rock
  wheels, blasting.
• Plowing reeled conduit, field drains

NATIONAL CONTRACTORS
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Order of magnitude

• Fiber optic conduit trenching 50-100/ft
• Conduit pipe jacking,
• directional drilling 200/ft
• Larger 2- to 4-ft-dia micro tunnel 500/ft
• Optimum-sized TBM tunnel 1500/ft
• Larger TBM tunnels 3000/ft

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Large Excavations for Support Facilities, Nuclear
Reactors
SHAFTS CHAMBERS

• Take advantage of underground
• Build arches, not beams
• Shielding provided by rock
• Avoid difficult ground, soil/rock contacts
• in the rock chambers
• Groundwater control essential
• Pro-active planning/design team
• Investigation and assessment of environmental
  impacts
• Establishment of better management and
  contracting practices
• Community relations
• Licensing
• QA/QC programs
• Dont try to force-fit above-ground criteria to
  underground construction
• Learn lessons from previous DOE underground
  projects.

SOIL
ROCK
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Experience with Large Excavations

• Subway stations, NORAD,
  
• underground powerhouses in rock
  
  60 to 100 ft wide
• Deep access shafts extending into rock
• through 200 - 300 of water-bearing sands
• using concrete diaphragm walls, freezing,
• 200-ft-diameter circular shafts constructed in
  clay
• DOE Underground Projects large interaction halls
• NUMI at Fermi-lab in limestone
• 200 ft deep open excavations designed for Texas
  SSC in shale.
• DOE Underground projects tunnels
• Exploratory TBM tunnel (25) for site
  suitability, Yucca Mountain
• TBM tunnels for SSC ring, Texas
• Shotcreted tunnels for SLAC, Palo Alto

SHAFTS CHAMBERS
SOIL
ROCK
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Mainline of Supergrid tunnel scale?

• Rock tunnel boring machines (TBMs) with disk
  cutters
• Most economic
• 10- to 15-ft-dia (depending on tunnel length
• gt 5000 ft drives

• Soil tunnel shields, pressurized face
• Bentonite slurry or conditioned muck (Earth
  Pressure Balance, EPB) to support face
• Install one pass (final) segmented lining in
  shield as shield advances
• Soil TBMs can be fitted with disk cutters to cut
  rock and boulders, but driving tunnels on
  contacts between rock and soil should be avoided.

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Requirements for construction shafts, access,
junctions, chambers, booster stations
Shafts
SOIL ROCK
SOIL ROCK

• Spacing along tunnel line
• Depth
• Size

10 to 15 ft

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Multiple use corridors large tunnels

• Rail
• Freight, double stack
• Passenger, twin tunnels 20-ft-dia
  limited additional space
• Passenger, single tunnels 35-ft-dia
• Fire Life Safety concerns
• High speed corridors likely to require high
  population density
• Portion of tunnel cost supported by supergrid ?

?
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Drill and Blast
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Chattahoochie Tunnel, AtlantaTwo 20-ft-dia.
tunnel boring machines 47,000 ft
CUTTERHEAD
OPEN SHIELD
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Cutter head Back-loading (recessed) disk
cutterscutting tracks approx. 4 in. apart
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GRIPPERS AGAINST ROCK.
THRUST CYLINDERS SHOVE CUTTERHEAD FORWARD
(Photo shows machine being assembled in drill and
blast section)
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MINIMUM ROCK SUPPORT ROCK BOLTS
VENTILATION LINE
CONVEYOR BELT FOR MUCK
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DISK CUTTERS Penetration rate - - in
proportion to Thrust/cutter rpm
Thrust 1960 soft rock 1980 30,000 lb/
cutter 2000 70,000 lb /cutter the result of
improved tool hardness, bearing design
metallurgy.
Advance Rate Pen. rate x
Utilization ( of workday machine is
penetrating)
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• Pressurized face tunnel boring machines
• now the standard tunneling method for soils
  that would otherwise flow or run into the tunnel
  face. Allows tunneling through water-bearing
  soils without dewatering.

• SLURRY SHIELD (Common for micro-tunnels)
• Chamber at front of shield is filled with a
  bentonite slurry mixed with excavated muck to
  provide a pressure against the face. Slurried
  muck is removed from chamber and pumped out of
  the tunnel through a return slurry pipe.
• EARTH PRESSURE BALANCED (EPB) SHIELD
  (Common for large tunnels in soil)
• Chamber at front of shield is filled with
  excavated muck mixed with additives to provide a
  pressure against the face. Muck is removed from
  chamber with a screw conveyor.

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• Earth Pressure Balanced Shield

Muck pressurized muck in chamber supports face
Screws remove muck and provide back pressure
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Segmental Lining is installed in tail end of the
shield. Shield is advanced by pushing against
the installed lining
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Soap foam, polymer is injected to reduce friction
and fluidize muck so that face pressure can be
developed
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Disk cutters to cut boulders, rock
Grizzlies to limit size of boulders passing
through the head
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Small Scale Conduit

• Micro Tunneling pipe jacking
• Diameters from 2 ft to 10 ft.
• Less than 3-ft-diameter no entry
• Horizontal Directional Drilling
• 6 to 48 in. diameter
• Short runs (200 1000 6000)
• Open Excavation
• Plowing cable reels
• Trenching
• Trenchers, Excavators
• Rock chain driven cutters with rock picks, rock
  wheels, blasting. Preferred excavation method is
  not just what can be done but what is efficient.

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• MICRO TUNNEL SLURRY SHIELD
• Rotating cutterhead, bentonite slurry supports
  face
• Slurry is circulated out of tunnel to remove
  excavated muck
• After muck is separated, slurry is recirculated
  to tunnel face

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Total Jacking Force
PIPE SECTIONS ARE ADDED IN JACKING SHAFT. Micro
TBM IS PROPELLED BY JACKING THE STRING OF PIPE
FORWARD
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JACKING PIT START OF MICRO TUNNEL
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• JACKING FRAME IN STARTING PIT
• Place 10 to 12-ft-long pipe, with slurry lines
  attached
• 30 minutes to install pipe section
• Jack pipe string to advance the shield

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LOWERING PIPE SECTION INTO PIT
FOR JACKING
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HORIZONTAL DIRECTIONAL DRILLING (HDD)
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• HDD CAPABILITIES TO DATE
• Maximum distance 6000 ft at 24 in. dia.
• Maximum diameter 48 in. over distance of 3000 ft
• Excavation and Steering
• EM signal transmitted to surface or through
  single hard wire line in casing inclination
  and magnetic azimuth
• Circulating fluid pumped to mud motor or jets to
  excavate ground. Steering controlled by small
  rotations of pipe to adjust attack angle of the
  motors or cutting tool.

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Management and Contracting Practices

• 1970s Excessive litigation on tunnel projects
  desire to avoid adversarial relations that
  affected project cost, schedule, quality.
• As a result, tunneling industry became the leader
  in the development of better contracting
  practices and dispute resolution processes.
• Three- person, independent Disputes Review
  Boards non binding arbitration real time
  resolution of issues on the job
• Geotechnical baseline reports data from borings
  alone do not adequately describe site conditions
  owner defines anticipated ground conditions to
  aid bidding and reduce disputes.
• Recognize that Differing Site Conditions clause,
  which is standard to Federal contracts, means
  that the ground is the owners, and risks
  associated with the ground conditions must be
  assumed by the owner.
• Design and manage the project first, to avoid
  risk, then to equitably assign risk, and clearly
  define responsibility for risks.
• Use of owner-provided contingency funds for low
  probability, high risk events that are difficult
  for contractor to estimate and bid.
• Provide unit prices for items that contractor
  does not control.
• Some tunneling projects are considering use of
  design-build, and other contracting forms that
  combine technical and cost proposals

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• 1970s
• DOT-sponsored RD and demonstrations.
• Washington Metro start-up 100-mile subway
  construction
• SSC Project
• 16-ft-diameter tunnels 50 miles under
  construction.
• 200-ft-deep interaction halls.
• Design and construction coped with swelling shale
  formation not anticipated in Texas proposal.
• PBMK Team Underground construction on schedule
  and under budget.
• Yucca Mountain exploratory tunnel for site
  suitability
• 25-ft diameter tunnel worlds largest
  exploratory tunnel.
• QA/QC for nuclear facilities often
  inappropriately applied to tunnel construction.
• cost plus construction, large bureaucracy
• coordination between science (site suitability
  investigations) and tunneling
• Tunneling revealed conditions unknown from other
  exploration, provided platform for experimental
  work.
• Fermi Lab NUMI.
• SLAC, Fermilab Next Linear Collider

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The industry does not have organizations that
invest significantly in long term R D

• Engineering firms small (No Mitsubishis)
• Contractors focus on each contract, high risk
  limits innovation.
• Trenching and trenchless (micro-tunnel,
  directional drilling) contractors innovations
  have been made, but most are small operators.
• Equipment manufacturers utilize available
  technology
• Exploration, instrumentation borrow tools from
  oil industry
• Owners Washington Metro supported field research
  in early phases of project, most owners do not.
• U.S. DOT supported demonstration projects and
  applied research in tunneling in the early 1970s
• 2002 Amsterdam Metro an owner committed to major
  applied research and development program in order
  to control settlement of soft clays and silts
  below water table and limit damage to historic
  structures by
• designing tunneling machine shield, working with
  machine manufacturers to minimize ground loss
  during tunneling.
• conducting full scale tests of grouting
  procedures to compensate for ground movements
• developing methods for analyzing and estimating
  settlements and controlling the tunneling process
• investigating contracting practices to manage
  risks, and distribute them between owner and
  contractor

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• Curvature
• Diameter
• Moisture/water control
• Access, Maintenance
• Shafts, booster/mechanical stations, junctions

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Supergrid Opportunities

• Long-term project
• Large capital costs for installation
• Special requirements for installing the grid
  tunnel size, lengths of runs, ranges of ground
  conditions to be encountered.
• Trend with time less space and more difficult
  access for installing utlities. Less public
  tolerance for disturbance
• Increasing use of tunneling and trenchless
  technologies rather than trenching and open
  excavation.
• Focus for improving tunneling technology for
  supergrid
• Contracting practices mitigation and assignment
  of risk
• Joint efforts with research groups, engineering
  firms, contractors, and machine manufactures to
  develop and demonstrate excavation and tunneling
  systems that will fit the requirements of the
  project
• Link directional drilling, micro-tunneling and
  larger tunnel boring machine technologies.
• Support demonstration projects using advanced
  technologies for driving tunnels.

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Hole through
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ROCK GROUP

• Better Contracting Practices