norwegian subsea tunnelling concept with emphasis on ... · woldmo o., 2007, injection technology...

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


Outline

Background

Norwegian tunnelling concept

Groundwater control

Significance of geological parameters for predicting water

inflow in hard rock tunnels


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


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


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.


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)


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


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


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


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”


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



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


Norwegian sub sea tunnel concept

14

REQUIRED TODAY (NPRA):

min. 50m unless favorable conditions documented


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


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



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



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


Fixed price contract (first and only)

Unforeseeable conditions

The contractor lost the court trial


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



Probedrilling

Groundwater control in Norwegian sub-sea tunnels


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);


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


Pre-grouting pattern:

Aiming for creating a layer of 3-5 m water-tight outside the tunnel;



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;



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



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


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


- 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



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


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


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.


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.


The Romeriksporten tunnel


The Frøya tunnel


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


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


Summary of degree of support for

the respective hypotheses

37


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)


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

norwegian subsea tunnelling concept with emphasis on ... · woldmo o., 2007, injection technology...

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