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SINTEF Building and Infrastructure 1
Norwegian subsea tunnelling
concept with emphasis on
groundwater control
PhD Kristin H. Holmøy
Research Manager Rock Engineering Group
Chairman of the Norwegian Group for Rock Mechanics
Seminar 6th November
NTU-JTC Industrial Infrastructure Innovation Centre
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Outline
Background
Norwegian tunnelling concept
Groundwater control
Significance of geological parameters for predicting water
inflow in hard rock tunnels
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Background
My first job was at the railway tunnel Romeriksporten
High water inflow
Settlements of buildings
Groundwater lowering – one small lake almost dissapeared
Excavation was delayed – opening of tunnel one year delayed
Negative media attention
Second job was at the Frøya subsea tunnel
Groundwater control very important
Improve the understanding of different geological
parameters
Make reliable prognosis for water inflow
SINTEF Building and Infrastructure
Norwegian fjords and opportunities
for strait crossings
4
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There are many good reasons to
establish strait crossings in Norway
5
Snow avelanches and rockfalls may increase
due to:
• Increased precipitation
• Milder winters
• Warmer summers
• Heavier storms
Norwegian Public Roads Administration
SINTEF Building and Infrastructure
Bridges, tunnels and ferries connect
islands to the mainland road network
6
Areas (red) where
tunnels have
triggered fixed
connection to the
mainland
The
Norwgian
coast line
including
islands and
fjords is
57.000km
long.
As a
comparison
the Earth is
at equator
40.000km.
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Norwegian Sub Sea Tunnel concept
• Atlanterhavstunnelen opened in 2009
• Ryaforbindelsen opened in 2011 (Northern Norway)
• Karmøy- and Knappetunnel under construction
• Ryfast and Rogfast under planning (next to
Stavanger)
Vardø was the first sub-sea tunnel (1983)
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Norwegian sub sea tunnels entirely
through bedrock tunnelling concept
Used for roads and pipelines
Typically crossing sounds 1 – 4 km wide, bedrock at 30 -
300+ m depth b.s.l.
Substantially lower cost than bridges and submerged
tunnels, even with long tubes and challenging geology
More than 30 completed road sub sea road tunnels since
1982
1 in Iceland, 2 in Faroe Islands, all: single tube
Several projects have been looked at in other countries
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Norwegian Sub Sea Tunnel
concept
PROJECT YEAR CROSS GEOLOGY LENGTH MIN. ROCK MAX. AADT SECTION (km) COVER (m) depth
m2 (m.b.s.l.)
Vardø 1981 53 Shale/sandst. 2.6 28 - 88 670
Ellingsøy 1987 68 Gneiss 3.5 42 -140 2700
Kvalsund 1988 43 Gneiss 1.6 23 - 56 500
Godøy 1989 52 Gneiss 3.8 33 -153 725
Nappstraumen 1990 55 Gneiss 1.8 27 - 60 600
Freifjord 1992 70 Gneiss 5.2 30 -100 1850
Byfjorden 1992 70 Phyllite 5.8 34 -223 2800
Hitra 1994 70 Gneiss 5.6 38 -264 635
North Cape 1999 50 Shale/sandst. 6.8 49 -212 300
Oslofjord 2000 78 Gneiss 7.2 32 -130 4000
Frøya 2000 52 Gneiss 5.2 41 -157 530
Bømlafjord 2000 78 Gneiss/schist 7.9 35 -260 2500
Skatestraum 2002 52 Gneiss 1.9 40 - 80
Eiksund 2007 71 Gneiss/gabbro/ 7.8 50 -287
limestone
TOTAL NUMBER: 28
NORWEGIAN SUB SEA ROAD TUNNELS - KEY DATA /
CHARACTERISTICS OF SOME PROJECTS
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Norwegian Sub Sea Tunnel concept NORWEGIAN SUB SEA TUNNELS FOR WATER, GAS AND OIL -
KEY DATA/CHARACTERISTICS OF MAIN PROJECTS
PROJECT YEAR AREA GEOLOGY LENGTH MIN. ROCK DEPTH
(m2) (km) COVER (m) (m.b.s.l.)
Frierfjord (gas) 1976 16 Gneiss/clayst. 3.6 48 -253
Karmsund (gas) 1984 27 Gneiss/phyllite 4.7 56 -180
Førdesfjord ” 1984 27 Gneiss 3.4 46 -160
Førlandsfjord ” 1984 27 Gneiss/phyllite 3.9 55 -170
Hjartøy (oil) 1986 26 Gneiss 2.3 38 (6) -110
Kollsnes (gas) 1994 45-70 Gneiss 3.8 7 (piercing) -180
Snøhvit (water) 2005 22 Gneiss 1.1/3.3 -111/54
Aukra ” 2005 20/25 Gneiss 1.4/1.0 - 86/57
TOTAL NUMBER: 16
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Norwegian Sub Sea Tunnel GEOLOGICAL OPPORTUNITIES AND CONSTRAINS
The Scandinavian host rock varies
from poor to extremely good rock.
Folding, faulting and high tectonic
stresses influence stability in tunnels
Weakness zones can exhibit great
variation in quality, Q-values from
extremely poor to good.
The width of such zones may vary
from a few centimeters to tens of m
OneCHALLENGE: to deal with
frequently changing ground conditions
Another CHALLENGE: replace cast-
in-place concrete lining in poorer rock
It is typical Hard
Rock, but not
necessarily
“Good Rock”
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Norwegian Sub Sea Tunnel concept GEOLOGICAL OPPORTUNITIES AND CONSTRAINS
The material rock mass has a
number of excellent properties:
* It’s stress induced confinement
* It’s self-standing capacity
* It’s impermeable nature
* It’s thermal capacity
But it is neither
homogenous nor
continuous, suffering:
Cracks and joints
Weaknesses
Weathering
A typical jointed aquifer, water
occurs along the most
permeable discontinuities.
Hydraulic conductivity vary a
lot; 10-5m/sec to 10-12m/sec
“Stand-up” time implies that the
rock mass is not only a dead
load. Engineering approach to
take this capacity into account.
Rock strengthening may be
needed to secure specified
capacities
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Norwegian Sub Sea Tunnel concept
Project Area Covered By Water and Bottom Sediments
Often Major Faults / Weakness Zones to cross
Inclined/Descends From Both Sides
Infinite Leakage Reservoir/Risk of Drowning the Tunnel
Saline Leakage Water
MAIN CHALLENGES OF TYPICAL FJORD CROSSING TUNNEL
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Norwegian sub sea tunnel concept
14
REQUIRED TODAY (NPRA):
min. 50m unless favorable conditions documented
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Norwegian Sub Sea Tunnel concept GEOLOGICAL INVESTIGATIONS
Cost effective methods
are applied to gain
information about the
variety of the rock mass
Critical areas will have
special attention
Probe-drilling ahead of
tunnel face is an
established method for
investigations
Previous holes
Alternativ with 2 holes
Alternativwith 3 holes
CROSS SECTION LONGITUDINAL SECTION
~3m
~3m
New holes
Overlap
min. 6 m
~20 m
TUNNEL
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Despite extensive pre-investigations:
• ”unexpected” erosion channel
• ground freezing required
=> considerable extra cost
Due to 2. directional drilling:
• erosion channel identified
in time =>
- tunnel alignment lowered 30m
- time (and money) saved
Oslofjord-
tunnel
Bømlafjord
-tunnel
Norwegian Sub Sea Tunnel concept
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ELLINGSØY TUNNEL (1986-87)
instability at face, initial phase of ”PIPING”
• ROCK COVER: 45m
• WATER DEPTH: 70m
• FAULT ZONE WITH CLAY/
WATER SEEPAGE
SHOTCRETING UNSUCCESSFUL
=> RESULT :
7 m HIGH CAVE-IN AFTER 6 hrs.
METHOD FOR STABILIZING:
SEALING OF WORKING FACE
WITH 7 m CONCRETE PLUG
YET; NO PROJECTS BEING ABANDONED
Norwegian Sub Sea Tunnel concept
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BJORØY (1993-96)
high water inflow
• JURASSIC FAULT ZONE
• SAND WITH COAL FRAGMENTS
• VERY HIGH PERMEABILITY
REMEDIAL MEASURES:
1) COMPREHENSIVE GROUTING (incl Tube-á-manchettes)
2) SPILING/ROCK BOLTS /SHOTCRETE
3) BLASTING (reduced blast length)
4) SHOTCRETE ARCHES
Norwegian Sub Sea Tunnel concept
Fixed price contract (first and only)
Unforeseeable conditions
The contractor lost the court trial
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Near deepest point, 230 m.b.s.l.:
• High water inflow/high pressure
• Instability at tunnel face
=>
• Blocking of face, casting of concrete plug
• Extensive pre-grouting (~1500 tons)
• Short round lengths/extensive rock support
• Considerable delay (~1 year)
Atlanterhavstunnel
2006-09
Norwegian Sub Sea Tunnel concept
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Probedrilling
Groundwater control in Norwegian sub-sea tunnels
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Typical example of a criterion to trigger the pre-grouting:
If the probe drilling (L = 30 m) results in water leakage more than 5 l/min in one probe hole; or
More than one probe hole have water leakage of between 3 and 5 l/min (lower value is used for stricter leakage criterion);
Groundwater control in Norwegian sub-sea tunnels
Inflow Measured from Probe Hole(s) (l/min)
Limit of Residual Inflow (l/min/100m)
15 30 50
From a single hole not less than 20m long >1 >2 >4
From two to four holes each not less than 20m long >3 >6 >10
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Pre-grouting pattern:
Aiming for creating a layer of 3-5 m water-tight outside the tunnel;
Groundwater control in Norwegian sub-sea tunnels
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Stop criterion: can be one of the following criteria
Grout take 0 and pressure of 60 bars for 1 minute; max grout take 4000 kg/hole.
Grout takes 0 and pressure of 60 bars for 5 min.
Grout take < 2 l/min for 5 min with 25 bars overpressure;
Groundwater control in Norwegian sub-sea tunnels
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Pregrouting material:
Type of discontinuity and aperture
(fill material)
Typical Lugeon
value
Recommended grout material
Open channels / karst
(stone, gravel)
50 Cement with sand/gravel and accelerator/ expanding
admixture.
Polyurethane for stopping major inflow.
Major discontinuities, aperture 1 cm
(coarse gravel)
10-50 Cement with bentonite or plasticizer/ expanding admixture.
Polyurethane is useful for stopping flowing water.
Intermediate discontinuities, joints, aperture
0.3-1 cm
(gravel)
3-15 Cement with super plasticizer (SP).
Polyurethane is useful if there is flowing water.
Joints, aperture 0.01-0.1 cm
(coarse-intermediate sand)
1-5 Micro-cement with SP
Polyurethane, silicates, acryles.
Small joints, aperture 0.01 cm
(fine-intermediate sand)
1 Ultra fine-grained micro-cement with SP and/or silicates,
acryles, epoxy
Boge, K. & Johansen, P.M., 1995, Rock Grouting, Practical Handbook (in Norwegian) &
Nilsen B., Palmström A., 2000, Handbook No2 Engineering Geology And Rock Engineering, Norwegian Tunnelling Society – NFF
Groundwater control in Norwegian sub-sea tunnels
SINTEF Building and Infrastructure
Pre-grouting material: In Norway, there is a rule of thumb stating that grout
material can be injected to a joint with spacing 3 times the size of the grouting
particle;
In tunnels with strict residual inflow rate (l/min/100m) joints with aperture down to
0,02 mm must be sealed
3 Control the groundwater problems in Norwegian sub-sea
tunnels
Woldmo O., 2007, Injection Technology For Water Ingress Control In Tunnels, BASF presentation in SINTEF, 15th May 2007
SINTEF Building and Infrastructure
Estimating the grouting work:
Number of holes, arrangement depends on the grouting classes;
Refer to Holmoy, 2008 for more information about classes
3 Control the groundwater problems in Norwegian sub-sea
tunnels
Class 1: Rock mass
is good, so less
amount of grouting in
this area;
Class 2: Main work of
grouting for
groundwater;
Class 3: grouting for
stability rather than
for groundwater.
Class 1 Class 2 Class 3
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- With the recommended procedure, it is possible to achieve
the maximum inflow of 30 l/min/100m;
Tunnel Max. water inflow
encountered
Grouted length
(% of tunnel)
Total grout
consumption
Permanent
leakage
(l/min/1 probehole) Under sea Under land (Tons) (l/min/100m)
Vardø 65 12 0 83 38
Karmsund 300 5 11 64 8
Førdesfjord < 300 13 0 35 9
Følandsfjord < 300 1 5 8
Hjartøy 200 13 5 35 9
Ellingsøy 400 34 15 345 28
Valderøy 100 12 0 44 29
Groundwater control in Norwegian sub-sea tunnels
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Estimating the pre-grouting work is a very difficult task
We need to obtain a better model in estimating grouting work
Due to a weakness zone
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Topic of my PhD: Significance of geological parameters for
predicting water inflow in hard rock
tunnels
6 Norwegian tunnels have been analysed
Water inflow in probedrilling holes and pregrouting rounds
25 m long sections
Correlations between water leakage and geological
parameters
8 hypotheses have been tested
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8 hypotheses
1. The water inflow is smaller in rock mass with Q-values
lower than 0.1, than in rock mass with Q-values between
0.1 and 10
2. Water-bearing joints are oriented with an angle of
45°±15° relatively to nearby major faults. (based on
Selmer-Olsen’s (1981) theory).
3. Water-bearing discontinuities are sub-parallel (±30°) with
the major principal stress (σ1).
4. Water inflow will decrease with increasing rock cover due
to higher gravitational stress causing closing of
discontinuities.
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8 hypotheses (continued)
5. A lake/sea above the tunnel gives large water inflow, due
to high reservoir capacity.
6. Igneous rocks give larger water inflow than sedimentary
and metamorphic rocks due to their brittle character.
7. Major rock type boundaries (including sedimentary layers
with different compositions) give large water inflow due to
increased fracturing.
8. Large weakness zones with Q-values lower than 0.1 give
larger relative water inflow than minor weakness zones.
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The Romeriksporten tunnel
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The Frøya tunnel
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Skaugum (4400 m)
Lunner (1500 m)
T-baneringen (1025 m)
Frøya (1900 m)
Romeriksporten (1625 m)
0 1000 2000 3000 4000 5000 6000
Water leakage (l/min per 25 m)
Distribution of water leakage
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Correlation value
Degree of support Negative correlation values Positive correlation values
No support -0.2 to 0 0 to 0.2
Low to medium support -0.3 to -0.2 0.2 to 0.3
Support -0.5 to -0.3 0.3 to 0.5
36
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Summary of degree of support for
the respective hypotheses
37
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Were the hypotheses supported or not?
Hypothesis No. 1: Support (Q-value)
Hypothesis No. 2: Medium support (45º±15º)
Hypothesis No. 3: Support (parallel principal stress)
Hypothesis No. 4: No support (rock cover)
Hypothesis No. 5: No support (soil) / Support (lake)
Hypothesis No. 6: Low to medium support (rock type)
Hypothesis No. 7: Support (rock type boundaries)
Hypothesis No. 8: No support (width of weakness zone)
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Recommendations
The most important investigation is a thorough geological
mapping
Orientation of joints and faults/weakness zones is very
important
If possible, rock stress measurements should be carried
out in order to find major principal stress
Magmatic rocks, major rock type boundaries and free
water table above the tunnel should be considered factors
increasing the risk of high water leakage
Prognosis for water leakage should be made
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