MTR JULKAISUT, N:RO 1 Raportti Elokuu 2003

M A A N A L A I S T E N T I L O J E N R A K E N T A M I S Y H D I S T Y S R Y

F I N N I S H T U N N E L L I N G A S S O C I A T I O N

MTR ry

Kalliorakentamisen kilpailukyky - kehitysohjelma

Pasi Tolppanen & Pauli Syrjnen Gridpoint Finland Oy

INTE

Hard Rock Tunnel Grouting Practice in Finland, Sweden, and Norway - Literature Study

MTR JULKAISUT, N:RO 1 Raportti Elokuu 2003

Hard Rock Tunnel Grouting Practice in Finland, Sweden, and Norway

Literature study

ISBN 951-96180-3-1 (paperback) ISBN 951-96180-4-X (URL: http://www.mtry.org/julkaisutoiminta.htm) ISSN 1459-5648 (paperback) ISSN 1459-5656 (URL: http://www.mtry.org/julkaisutoiminta.htm) Copyright

MTR -FTA 2003

JULKAISIJA PUBLISHER

Maanalaisten tilojen rakentamisyhdistys, MTR ry

Finnish Tunnelling Association

2

Abstract Grouting has developed greatly in the last decade. Improvements of grout material and equipment enable better quality final products. Grouting has become an important and meaningful part of underground construction. The environmental requirements have also tightened more in recent years and the harmful lowering of the groundwater level is forbidden.

Cementitious materials are mostly used in rock grouting in tunnels. Furthermore, due to the high level of the tightness requirements, very fine-grained cements are more often used since very small fracture apertures must be grouted. Many different chemical grouts also exist on the market, but after some environmental accidents their use has been limited or even forbidden. Chemical grouts are mainly used in very difficult places for post grouting.

A great deal of effort has gone into grouting design and compliance control. It is not enough to just evaluate or measure the leakages of the final tunnel. The deviation and leakage of grouting holes are measured and control holes are drilled into the grouted section. Moreover, the limitations and requirements for grouts are defined and inspected - even at the site. While designing, the varying geological features are taken into account and tunnels are divided into sections of different grouting classes.

Experiences and opinions on grouting in Finland, Norway, and Sweden have been collected and published in this report. The material presented is based on the literature, interviews, site visits, and the authors' own experiences. Furthermore, the discussions at the follow-up group meetings are also important.

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Tiivistelm

Injektoinnissa on tapahtunut runsaasti kehityst viimevuosina. Materiaalien ja laitteistojen paraneminen on luonut mahdollisuuden yh laadukkaammille lopputuotteille. Injektointi on kytketty keskeiseksi osaksi kalliorakentamista. Mys ympristtekijt ovat korostuneet viime vuosina ja pohjaveden haitallista alenemista ei sallita.

Sementtipohjaiset massat ovat selkesti eniten kytetty kalliorakentamisessa. Viime vuosina on yh enemmn siirrytty erittin hienojakoisten sementtien kyttn sill tunneleiden vuotovesimrien kiristyneet vaatimukset on johtanut tarpeeseen tiivist yh hienompia rakoja. Mys kemiallisia injektointiaineita on markkinoilla runsaasti, mutta muutamien ympristkatastrofien tapahduttua on niiden kytt rajoitettu. Kemiallisia aineita on kytetty lhinn hankalissa kohteissa jlki-injektoinnissa.

Kiristyneet tiiveysvaatimukset ja etenkin mikro- ja ultrahienojen sementtien lisntyv kytt on ohjannut mys laitteiden kehityst. Keskeist on ollut sekoittimien ja pumppujen kehittyminen sek laitteistojen muokkautuminen jrjestelmiksi. Mys automaattisten rekisterintilaitteiden liittminen osaksi jrjestelm on auttanut laadukkaan lopputuotteen aikaansaamista.

Mys suunnitteluun ja laadunvarmistukseen on viime vuosina keskitytty enemmn. Pelkk lopputuotteen vuotomrien toteaminen ei riit vaan injektointireikien taipumia ja vesimenekkej mitataan sek porataan kontrollireiki injektoituun osuuteen. Mys injektointimassoille on esitetty omia laatuvaatimuksia, joita tarkkaillaan mys tymaalla. Suunnittelussa pyritn ottamaan alueelliset geologiset vaihtelut huomioon jakaen tunneli vaatimustasoltaan erilaisiin osioihin.

Tss raportissa on kertty kokemuksia ja nkemyksi injektoinnista Suomessa, Ruotsissa ja Norjassa. Esitetty aineisto pohjautuu kirjallisuuteen ja haastatteluihin sek kenttkynteihin ja kirjoittajien omiin kokemuksiin. Runsaasti tietoa ja kokemuksia on kuultu mys projektin seurantaryhmn palavereissa.

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5

Preface This report is a first phase study for the Finnish Grouting Instructions (INTE) project. INTE is part of the Competitive Rock Building development program organized by the Finnish Tunnelling Association FTA (MTR ry). Financial support for the project from Helsinki City Real Estate Department Geotechnical Division, Finnish Rail Administration, Finnish Road Administration, ELKEM ASA Materials, Master Builders Oy, Lemcon Oy, YIT Construction Oy, ITS-Vahvistus Oy, and Oy Atlas Copco Ab is gratefully acknowledged. The exchange of information and co-operation with Posiva Oy is also appreciated.

The project follow-up group was:

Raimo Viitala, Ilkka Satola / Helsinki City, Real Estate Department, Geotechnical Division

Harri Yli-Villamo / Finnish Rail Administration

Timo Cronvall / Oy VR-Rata Oy

Olli Niskanen / Finnish Road Administration

Steinar Roald, Olav Guldseth, Tor-Syland Hansen / ELKEM ASA, Materials

Ari Laitinen/ Master Builders Oy,

Hans-Olav Hognestad, Ola Woldmo / Degussa Ab

Bjarne Liljestrand / Lemcon Oy

Tuomo Tahvanainen / YIT Construction Oy

Arto Niemelinen / ITS-Vahvistus Oy

Ilkka Eskola, Sten-ke Pettersson, Heikki Rsnen / Oy Atlas Copco Ab

Reijo Riekkola / Saanio & Riekkola Oy

Tapani Lyytinen / Posiva Oy

Erkki Holopainen / Finnish Tunnelling Association

Pekka Salmenhaara / DeNeef Finland Oy

Esko Aaltonen / Muottikolmio Oy

Pauli Syrjnen, Pasi Tolppanen / Gridpoint Finland Oy

Furthermore, the authors would like to thank Ursula Sievnen / Saanio & Riekkola Oy, Vesa Vaaranta and Kari Korhonen / Lemcon Oy, Morten Rongmo / MIKA Contractor AS, Reidar Lvhaugen / Statens Vegvesen Tarald Nomeland / Elkem Materials ASA and Jukka Pll / Fundus Oy (on behalf of Finnish Tunneling Association) for their time, fruitful discussions and comments.

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Table of Contents

ABSTRACT ................................................................................................... 3

TIIVISTELM................................................................................................. 4

PREFACE...................................................................................................... 6

1. INTRODUCTION.................................................................................. 9

2. EVALUATION OF GROUTING REQUIREMENTS............................ 10

2.1 General ...................................................................................................................................10

2.2 Environmental requirements ...............................................................................................12

2.3 Requirements due to the cavern use ....................................................................................12

2.4 Strengthening of rock by grouting.......................................................................................12

2.5 Experienced gained from constructed tunnels....................................................................12

3. GROUTING MATERIALS.................................................................. 14

3.1 General ...................................................................................................................................14

3.2 Cementitious products ..........................................................................................................14 3.2.1 Properties............................................................................................................................18 3.2.2 Additives.............................................................................................................................20 3.2.3 Testing methods for cementitious materials .......................................................................23

3.3 Chemical grouts.....................................................................................................................26 3.3.1 Testing methods for chemical grouts..................................................................................29

4. GROUTING EQUIPMENT ................................................................. 31

4.1 Drilling Equipment................................................................................................................31

4.2 Platform .................................................................................................................................32

4.3 Mixer ......................................................................................................................................34

4.4 Agitator ..................................................................................................................................34

4.5 Grout Pump ...........................................................................................................................35

4.6 Pressure and Flow Meters and Recorders...........................................................................36

4.7 Automated Mixing and Grouting Plants .............................................................................36

4.8 Packers and other accessories ..............................................................................................37

4.9 Equipment for chemical grouting ........................................................................................39

5. GROUTING DESIGN......................................................................... 40

5.1 General ...................................................................................................................................40

5.2 Exploration methods for grouting need...............................................................................41 5.2.1 Working methods ...............................................................................................................48 5.2.2 Drill pattern design and grouting order...............................................................................48 5.2.3 Recipes and grouting speed ................................................................................................52 5.2.4 Grouting Pressure ...............................................................................................................52 5.2.5 Controlling grouting and stop criteria.................................................................................54 5.2.6 Post-grouting ......................................................................................................................56

6. QUALITY AND COMPLIANCE CONTROL....................................... 58

6.1 Quality control of grouts.......................................................................................................58

6.2 Control of grouting procedure .............................................................................................59

6.3 Acceptability control and actions due to unaccepted quality ............................................59

7. PURCHASE METHODS .................................................................... 61

REFERENCES............................................................................................. 64

APPENDIXES

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1. Introduction The aim of this literature report was to collect information about the hard rock grouting experiences and present status in Nordic countries, mainly in Finland, Sweden and Norway.

For this study, the recent research work by several institutes like Royal Institute of Technology in Stockholm, Norwegian University of Science and Technology in Trondheim and Helsinki University of Technology have been checked and referred to. Also, the experiences of client representatives, construction companies, as well as material and equipment producers, have been collected by site visits and personal discussions. In addition, there was an exchange of information with Posiva Oy (Nuclear waste management in Finland). The Finnish and Swedish grouting experiences are partly based on reports by Posiva Oy.

In Sweden and Norway, a great deal of effort has been focused on grouting research and practice. Also, the well-known unsuccessful projects in Sweden and Norway have increased the interest in grouting. So, it can be noted that the level of grouting knowledge and understanding in Finland should be increased, partly by utilizing the experiences of neighboring countries.

The current grouting material and equipment are high tech instruments and very suitable for the aggressive fight against leaking water to ensure dry tunnels and a stable environment. Also, the geological tools from site mapping to fancy computer-based models provide a very useful information base for evaluating leakage and for grouting procedure design.

This report will also be a basis for the Finnish Grouting Instructions that will be published in 2004.

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2. Evaluation of grouting requirements

2.1 General

The sealing requirements depend on:

environment (reduction of the water table), use of the underground facility, and, leakage during the construction phase.

Several analytical and empirical equations for water leakage evaluation at various purposes and depths have been presented. Cesano (1999, 2001) and Dalmalm (2001) present wide summaries of leakage evaluation methods in their thesis. Also, Sievnen (2001) evaluates different analytical methods in her licentiate thesis. She stated that an equation, which is based on the imaginary well approach, is the most reliable when the depth of the tunnel is about three times the level of the water table. The equation is discussed in more detail in Appendix A and used in the following examples. Thiems well equation is suitable for more shallow excavations (Airaksinen, 1978).

Water inflow into the cavern or tunnel is highly dependent on the hydraulic conductivity of the rock mass (Fig. 2.1); both for ungrouted and grouted zones. Also, the depth of the tunnel level, that is the water pressure, has an effect. This is, however, a more complicated factor to take into account since hydraulic conductivity is known to decrease by depth as can be seen in the Olkiluoto site (iks et al., 2000). The tunnel radius is less important (Fig. 2.2).

The rule of thumb is that the effect of joint opening on hydraulic conductivity follows the cubic theory. Thus, an opening two units wider presents an inflow 8 times higher. However, this is only valid when the fracture is consistent and channeled successfully to an unlimited aquifer by unlimited openings. Furthermore, factors like joint roughness, percentage of contact areas, infillings, etc. decrease the flow capacity. So, for each fracture flow the properties are much affected by boundary conditions not just the parameters of the fracture itself. This has been studied very much (for example by Hakami, 1995; Lanaro, 2001; Fardin, 2001; Zimmerman et al., 1991) for numerous applications and is still not completely solved as stated by Eriksson (2002).

10

0.00E +00

2.00E -08

4.00E -08

6.00E -08

8.00E -08

1.00E -07

1.20E -07

1.40E -07

1.60E -07

1.80E -07

2.00E -07

2.20E -07

2.40E -07

0 10 20 30 40 50

q, l /m in /100 m

k, m

/s

60

Figure 2.1. Water inflow to a tunnel vs. grouted zones hydraulic conductivity based on the formula A-2 shown in Appendix A. Assumptions: depth 30 m, hydraulic conductivity of ungrouted rock mass is 10-6 m/s (Lug ~ 10), thickness of grouted zone is 3 m, and skin factor for joint is 4 and tunnel radius 6 m.

0

10

20

30

40

100 150 200 250 300

q, l/m in/100 m

Tunn

el r

adiu

s, m

a)

0

10

20

30

40

2 2.2 2.4 2.6 2.8

q, l/m in/100 m

Tunn

el r

adiu

s, m

b)

Figure 2.2. Water inflow to tunnel versus tunnel radius; K = 1*10-6 m/s (Lug ~ 10), h= 30 m and skin factor = 4; a) ungrouted tunnel, b) grouted, by Ki = 1*10-8 m/s, and, thickness of grouted zone 3 m. Equations presented in Appendix A.

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2.2 Environmental requirements

Environmental requirements have been tightened in last few years especially in city areas. In most cases, it has been stated that excavation of underground tunnels or caverns should not lower groundwater table if it causes significant:

consolidation / subsidence of ground (especially in building areas), rotting of wooden piles under buildings, drying of wells, or, drying of vegetation if it should be preserved.

Based on the Swedish experiences, even an inflow amount of 5 - 10 l/min/100 m can be enough to cause a permanent decrease in the water table level (Hartikainen, 1973). In some cases in the Oslo area, an inflow of 1 - 2 l/min/100 m has been found to be too much for the groundwater table, Roald (2002). It is difficult to specify any exact values, since the influence can vary considerably from place to place due to the size of the local aquifer and water recharge.

2.3 Requirements due to the cavern use

The use of the excavated facility also sets requirements for water sealing. The strictest requirements for underground constructions, 0.5 - 5 l/min/100 m, are set for road and railway tunnels, and, for some special caverns like telecommunication shelters. In the case of low requirement caverns like water tunnels, the level of 40 - 80 l/min/100 m is typically used. However, these limits are also dependent on the other requirements such as environment.

2.4 Strengthening of rock by grouting

Barton et al. (2001) have presented an idea for strengthening rock by grouting. They have found that grouting affects the quality of weaker rock more than the better quality of rock. In very weak rock (Q < 0.3) the grouting effect is highest, even two to three Q-classes, but with the good and very good rock (Q > 10) the difference is very limited.

2.5 Experienced gained from constructed tunnels

Based on the Nordic experiences, the target of a few l/min/100 m tunnel can realistically be reached by conventional grouting technique in "a normal geological environment". Also, the environmental effects due to the water inflow were eliminated quite well by grouting (see Appendix B). It has been noted that the inflow of groundwater can be as low as 1 l/min/100 m tunnel after grouting for a large cement grouted tunnel (100 m2),

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and excavated some 10 - 50 m below water table (for example, Bckblom, 2002; Roald, 2002; Statens Vegvesen, 2001; Stille, 2001). Though, some unlucky experiences also exist. For example, in the case of the Turku-Naantali water tunnel pre-grouting was destroyed by not waiting long enough and the inflow waters were moved to nearby fractures after post-grouting (Sievnen & Hagros, 2002). Similar phenomenon happened in Norway in the Tsen tunnel where several reasons led to an unsatisfactory sealing result (Statens Vegvesen, 2001). In many cases, one or two major fractures or crush zones control most of the inflow amounts - even after a trial grouting; for example, at Olkiluoto & Loviisa VLJ repositories (Sievnen & Hagros, 2002). Furthermore, we should also not forget the environmental and economic catastrophes at Hallandssen and Romeriksporten.

In some cases from Finland, Sweden, and Canada the seepage decrease in time might be 0.3 - 1.1 % / month (Bckblom, 2002). The reasons for this are not understood, but one explanation is that it is due to precipitation of calcite and/or bacteria, degassing, and rock creep, etc. But as at URL, there might be a remarkable decrease after excavation work (30 m3/day => 20 m3/day in the first two years), but leveling out during that time - at URL the current leakage has settled at 10 m3/day.

Several opinions concerning the limit of achievable hydraulic conductivity exist:

The achieved maximum tightness varies between 1*10-7 m/s - 2.5*10-9 m/s, depending on the materials used and the geology around the tunnel (Bckblom, 2002).

Experiences in Oslo show that it is difficult to grout if the hydraulic conductivity is lower than 2.5*10-9 m/s (comment found in Hallandss documentation, Bckblom, 2002).

Using ordinary cement, a final result of K = 3*10-7 m/s is a practical limit (Stille, 2001).

The channels with an aperture smaller than 30 m (equal to K = 10-9 m/s) can be assumed to be wholly or partially unfilled by grouting, even with dynamic grouting with very fine cement (max grain size 15 m) conclusion in the Stripa project (Pusch et al., 1985).

Generally accepted rules-of-thumb say; apertures >0.1 mm are groutable with microcements and the aperture/cement grain size ratio should be > 3 (for example, Roald, 2002).

It was found in the Hallandss project that the mean flow reduction-% varies from 21 - 81 % for cements and 95 - 98 % for chemical grouts (2 different recipes), and 15 - 93 % for a mix of cement and chemical grouts (3 recipes) (Bckblom, 2002).

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3. Grouting materials

3.1 General

The selection of grouting material should be based on the tightness and environmental requirements, and the geological and hydrogeological properties of the rock mass. Grouting materials for rock can be divided into:

cementitious chemical a mix of cementitious and chemical compounds

The materials used in the reported Finnish cases are mostly cementitious materials, normally Rapid cement or microcements (Sievnen & Hagros, 2002). Chemical grouts were used in only a few cases. The experiences are similar in Sweden where several experts favor the fine fraction grouting cement (Bckblom, 2002; Dalmalm, 2001; Stille, 2001, Vgverket, 2000). In Norway, microcements or ultrafine cements are increasingly used (Statens Vegvesen, 2001).

3.2 Cementitious products

Cementitious products, suspensions, are mostly used for rock grouting. The lasting properties and environmental aspects for cements are well known, and cements are relatively cheap. Their properties and usability can be adjusted by water/cement ratio, additives, admixtures, and by choosing a suitable grain size distribution (normal or fine grounded cements).

Grouts can be based on Portland cement, slag cement, or aluminum cement. Portland cement is usually used. Slag cement has a longer curing time and aluminum cement a shorter curing time than Portland cement. The maximum storage time for cements varies from 3 to 6 months.

Cements can be divided into different classes based on their grain size distribution (see also Fig. 3.1):

Ordinary Portland or Construction Cements (OPC, d95

a)

0

20

40

60

80

100

0,1 1 10 100Sieve size ( m)

Pass

ing

perc

ent (

%)

Spinor A6

Spinor A12

Mikrodur R-X

Mikrodur R-U

Alofix-MC

Cementa UF 12

MBT Rheocem 800(7A-2; Oslo)

b)

0

20

40

60

80

100

0,1 1 10 100Sieve size ( m)

Pass

ing

perc

ent (

%)

Mikrodur R-F

Cementa UF 16

MBT Rheocem 650

MBT Rheocem 800

MBT Rheocem 900

c)

0

20

40

60

80

100

0,1 1 10 100 1000Sieve size ( m)

Pass

ing

perc

ent (

%)

Spinor A32Mikrodur R-SCementa Inj 30Cementa Inj 64Cementa AnlPikaRapidYleis

Figure 3.1 Grain size distribution of the grouting cements divided into three classes: a) UFC d100 20 m, b) MFC d95 20 m, c) coarser grouting cements / OPC d95 > 20 m. The curves are based on the material manufacturers information.

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The European standard for grouting gives a limit value of d95

cements, a typical presented size of d95% might, in some cases, be too low. As seen in Figure 3.1, there can be much larger grains (a tail) in the final 5% passing. To estimate the penetrability of grout, a passing percent of 98 or even 100 could be more practical. Further, it should always be noted what the manufacturers maximum grain size actually means!

Figure 3.2. Relation between joint opening, grain size, and grouting cement type (Hansen et al., 2002).

In Finland, the use of microcements has grown in recent years; for example, Rheocem 650 has been used to seal Merihaka sports hall & civil shelter and Ultrafine 12 cement at Salmisaari coal storage (see Appendix G). However, Rapid cement or OPC are still widely used. Cement takes from ten to hundreds of kg/bore-hole meter. When calculating cement consumption 10 kg/bore-hole meter is normally used. No major problems were encountered, or at least reported, but in several tunnel / caverns steel drip cups have been installed.

In Sweden Injektering 30 is mostly used. Also, more fine-grained cements are used, but a few sites have complained that the very fine particles (

To summarize, it can be stated that increased tightness requirements lead to the selection of micro- or even ultrafine cements.

3.2.1 Properties

The grouting result achieved by cement-based grout is highly dependent on the ability of the grout to penetrate the fractures. Penetration is dependent of the flow properties (yield value, viscosity), stability against sedimentation (bleeding), and grain size distribution of the cement particles (Hkansson, 1993). As presented in Figure 3.2, the rule of thumb is that the maximum particle size of the grout should be 1/3 of the fracture aperture for successful grouting. However, care should be taken to ascertain the correct maximum size stated on the container by the cement manufacturer.

The filtration in narrow passages is assumed to have a large influence on the penetration. Dalmalm (2001) and Eriksson (2002) have shown, by a laboratory filter test (see Fig. 3.9) with a low-pressure filter pump that filter cakes occur more often with micro- or ultrafine cements. Not all the experts accept this, however, since results from the NES (see Fig. 3.8) test using proper admixtures and pressures show that filtering can be avoided (Roald, 2002).

Penetrability of the grout is not the whole story. Though penetration can be achieved, a stage of joint filling or not filling - should still be taken into account. As presented in the thesis by Eriksson (2002) and in studies by several authors (for example,. Pusch et al., 1991) filling a joint is dependent on the grain size of the cement particles, and how stabile the grout is against the particle separation. Moreover, grout stability has been seen to be influenced by the water/cement-ratio. Of course, the fracture geometry, aperture, and contact areas also exercise an influence.

Figure 3.3. Fissure filling by grouting. A stands for a wider channel, which is completely filled with grout, B is a partly filled area, and C is the unfilled area (Pusch et al., 1991).

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The hardening and the strength of a grout have also been under discussion and found to be important parameters for evaluating the success of grouting. The rheology is shown to be highly dependent on several factors as presented in Table 3-2 (Hkansson, 1993). Further, it should always be noted that grout properties change with time.

Table 3-2. Influence on the rheology induced by different properties and additives (Hkansson, 1993).

Additive / action Influence on: Yield stress* Viscosity* Binding time*

Decreased w/c-ratio + + + + + + - -

Increased specific cement surface + + + + - -

Decreased temperature + + + + +

Addition of bentonite + + + + + / -

Addition of silica + + + + + -

Addition of superplasticizer - - - - - - + +

Addition of sodium silicate + + + + -

Addition of calcium chloride + + - - -

*) + + + large increase - - - large decrease

+ + moderate increase - - moderate decrease

+ small increases - small decrease

+ / - no increase

The maximum tightness achieved with cement grouts varies between 1*10-7 m/s (~1 Lug) - 5*10-9 m/s (~0.02 Lug) depending on the materials used, grouting methods (equipment, pressure, etc.), and geological conditions (see Chapter 2.5). Professor Stille (2001) has stated that using ordinary cement a final hydraulic conductivity of K = 3*10-7 m/s (~2 Lug) is the practical maximum tightness.

Geometrically (and theoretically) 0.5 liters of grout covers:

about 10 m2 joint surface with 50 m joint opening, about 6.7 m2 joint surface with 75 m joint opening, and, about 5 m2 joint surface with 100 m joint opening.

As well as grain size distribution, penetrability, viscosity, yield- or compressive strength and stability, the parameters like price, gelling time, storage and shelf life, availability

19

and toxicity of the grout should always be taken into account when choosing the right material.

3.2.2 Additives

Cement-based grout additives can be admixtures, bentonite, mineral additives, or pozzolan, such as blast furnace slag or silica fume. Admixtures used for cementitious grouts are, for example:

plasticizers and superplasticizer to reduce the water-cement ratio, accelerators to prevent grouts from leaking into the tunnel or ground surface, additives to reduce bleeding and shrinkage, expanding additives, retarders to slow hydration.

Typically material producers have their own admixture products that are recommended for use in the mixtures with the actual cement product.

Standard SFS-EN 197-1 for cements states that the dosage of admixtures, which are used to improve the properties of cements but not concrete, must not be more than 1% of the weight of the cement. This is not valid for additives like pozzolan, fly ash, calcium sulfate, or silica. In the standard SFS-EN 206-1 for concrete, the amount of additives is limited to 50 g / cement-kg, unless a higher amount is known to affect the functional or longevity properties. However, the dosage should not exceed the manufacturers' instructions.

3.2.2.1 Additives to reduce bleeding and shrinkage

Bleeding of the grout and shrinkage of the hardened grout are problems with cementitious grouts. To avoid these, and also to increase penetrability, bentonite or silica-based products like GroutAid can be used. Also, a low w/c-ratio (w/c = 0.71.0 depending on the cement) reduces bleeding and shrinkage.

Bentonite is volcanic clay (smectites), which can absorb large amounts of water. Bentonite is inert and normally added to stabilize the grout against separation. Its water absorption ability is more than 500%. Since the introduction of microcements, the use of bentonite has decreased, because microcement-based grouts are much more stable, even for relatively high w/c-ratios, than OPC grouts. This is because the high specific surface (e.g. Blaine-value) of fine-grained cements binds more water. The bentonite will also make the grout more thixotropic. In Figure 3.4, the stabilization effect of a varying dosage of bentonite can be seen.

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Figure 3.4. Average sedimentation rate of bentonite stabilized cement suspensions (specific surface area of cement 3500 cm2/g. 1) Sedimentation rate H/H (%), 2) Addition of bentonite (% with reference to the weight of cement), 3) w/c-ratio (Kutzner, 1996).

The use of GroutAid silica slurry has been found to decrease bleeding - even with quite a high w/c-ratio (Fig. 3.5). It also improves the penetration properties of the grout (Fig. 3.6). The presented tests were carried out using Ultrafine 12 cement.

0

10

20

30

40

1.0 1.5 2.0 3.0 6.0water / powder ratio

Wat

er s

epar

atio

n af

ter 2

hrs

[%]

without GroutAidwith GroutAid

10%GA 25%GA 50%GA30%GA20%GA

Not tested.

Limit for stable

Figure 3.5. Water separation in grout after 2 h; Ultrafin 12 cement, varying dosage of GroutAid (x% GA) and different w/c-ratio (Hansen et al., 2002).

Some cements, like Rheocem, are said to be stable (bleeding less than 2% within 2h) without any extra additives.

21

To increase the sealing effect of the grout, some expanding agents can be used. These are, for example, an admixture of fine-milled aluminum or aluminate sulfate and activated coal, which releases gas bubbles while moisturizing. Further, an expansion of the grout can also be achieved by using burned chalk (CaO) or periclas (MgO). An expansion, similar to snail dynamite, will occur when these hydrate to calcium or magnesium hydroxide.

NOTE! Even if the grout is tested in a lab and found to be stable (bleeding < 2%) it may lose its stability (down to 10 - 15%) when a sample is disturbed. This phenomenon has been found to occur and depends on the cements mineral and chemical composition (Roald, 2002).

Sand Column, d50=0.17 mm

0

10

20

30

40

0 10 20 25Content of GroutAid [%]

Pene

trat

ion

into

Silv

ersa

nd 1

7 [c

m]

w/p = 1.5w/p = 2.0

Not tested.

Figure 3.6. Effect of silica-based additive (GroutAid) on grout penetration in Sand Column test - two water/powder ratio is used (Hansen et al., 2002).

3.2.2.2 Plasticizers

The Most commonly used plasticizers are surface-active superplasticiziers. With reduced cement grain size, the inter-particular forces between the grains are increased. The grains become electrically charged and attract each other. In order to break these bindings, surface-active superplasticiziers can be used for a steric- or electrostatic repulsion of the cement grains. Typically, the water/cement ratio with plasticizers is between 1.0 - 1.3. Without plasticizers the w/c- ratio used is typically 3 - 4.

Both the naphthalene- or melamine-based superplasticizers can be used, though they might have varying effects on different cement types, depending on the dominant cement compound, and also on the w/c-ratios. An admixture, such as superplasticiziers, generally affects the grouting in a positive way in that the grout can penetrate and reach further before hardening begins.

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3.2.2.3 Accelerators

The accelerators can be divided into two categories:

binder accelerators that lead to the early hardening of the grout, and strength accelerators that lead to an increase of the early strength.

The most common accelerator is calcium chloride, which affects both the binding and the early strength development. For extreme cases up to 15% of calcium chloride could be used, however, the grout will then lose the long-term stability and decay. It should be noted that calcium chloride is a retarder for aluminate and slag cements. Other early strength accelerators are, for example, potassium carbonate, sodium carbonate, calcium formate, triethanolamide, calcium acetate, calcium propionate, and calcium butyrate.

Binder accelerators include sodium silicate (waterglass), sodium aluminates, aluminium chloride, sodium floride, and calcium chloride. Aluminate cement in Portland cement also behaves like an accelerator.

Accelerators can be added either to the mixer to shorten the setting time or to the packer for a fast reaction. However, mixing due the relatively slow grout speed (0 - 20 l/min) might induce mixing problems and a possible reaction in packer can create plugs. One solution might be to use effective alcali free accelerators together with Portland cement and POC based micro and ultrafine cement (Laitinen, 2003).

Elkem AB offers a two component grouting system called MultiGrout (magnesium cement and CaCl as an accelerator). In this system, the setting time can be adjusted to 10 - 90 min.

3.2.2.4 Retarders

The use of retarders is not so common in grouting, but ligno-sulfonate can be used if needed. MBTs Delvocrete offers a system for grouting (and also for shotcreting). It includes a special stabilizer and an activator, which is added to the mixer. This system has been used in very warm environments where problems caused by too early setting have been encountered. With a stabilator, a ready mixed cement based grout will remain fresh for up to 3 days.

3.2.3 Testing methods for cementitious materials

Penetrability of the grout can be analyzed by using so called Sand Column -test, by measuring a traveling length of grout through the sand filled plexiglas pipe (Fig. 3.7).

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Grout pumped from this side

90cm long plexitu

be

Grout pumped from this side

90cm long plexitu

be

Figure 3.7. Sand Column test system for grout penetrability.

Cement manufacturers present the results of the Sand Column test as a property of their product, but typically the grain size of the filling sand and/or pumping pressure varies actually there is no specified system for the test as can be seen in the following examples:

* Ultrafine 12 with w/c=2 and 20 % GroutAid (silica based penetrator) has penetrated 85 cm into the water-filled sand NR50 with 2 bar pressure,

* Cem I 52.5 with w/c=1 and 2 % Rheobuild 2000 PF (dispersing agent) has penetrated 15 cm into the water-filled 0.1-0.5 mm quartz sand with 4 bar pressure, - for the same material the Marsh-cone value was 32 sec (MBT, 2001),

* Rheocem 650 with w/c=1 and 2 % Rheobuild 2000 PF (dispersing agent) has penetrated 90 cm into the water-filled into 0.1-0.5 mm quartz sand with 4 bar pressure; for the same material the Marsh-cone value was 32 sec (MBT, 2001).

Another test method is NES (Fig. 3.8), where grout material is pumped through the artificial smooth fracture at a constant pressure.

Figure 3.8. NES test for penetrability analysis

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A third method for penetrability test is a filter pump (Fig. 3.9a), where grout mix is manually sucked into the 500 mm long metal tube through a specified woven metal wire cloth (125, 75, 45 or 32 m; ASTM E 437). Method is modified for field tests at KTH, Laboratory of Soil and Rock Mechanics. Amount of grout (in milliliters) in tube is then measured. A bit more complicated system is developed to laboratory (Fig. 3.9b), where with quite low pressure of 0.5 bar a similar test is produced.

a) b)

Figure 3.9. a) Field test pump for filtration stability, b) Laboratory filter pump -system for penetrability analysis.

Density measurements can be used to check that there are no mixing mistakes in the grout. At site density can be measured by using a mud balance system (Fig. 3.10). Shrinkage of the cements can be measured from test cubes. An accepted value for shrinkage should be selected case by case though not more than 1 - 2% in the case of grouting for high-level caverns.

Figure 3.10. Mud-balance testing equipment (Pettersson & Molin, 1999).

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The grout flow properties or viscosity are determined using a Marsh funnel (Fig. 3.11a). The funnel is first filled with 1.5 l of grout. A measuring cup containing 1 US quart (946 ml) is filled from the standard funnel and the time is measured. Clean water has a reading of 26 sec (US quart) or 28 sec (1 liter). A suitable value for a grout is 32 - 35 sec.

a) b)

Figure 3.11. a) The March Funnel test for viscosity analysis (Pettersson & Molin, 1999), b) Bleeding test for stability analysis

Bleeding can be measured by pouring the grout into a 1000 ml graduated glass (Fig. 3.11b). After 2 hours, the height of the bleed water (H) is measured. With high-level requirements, bleeding should be

some products (pre- and final product) might be a work safety risk (irritation if touching the skin, etc),

longevity and stability properties not well known for all the materials some tests were carried out by Swedish National Research Center SP for TACCS (Salmenhaara , 2003),

use might require special equipment, due to the effective penetration, chemical grouting is faster than cement grouting

(Liljestrand, 2002).

due to the early expansion, some products do not flush away easily (Salmenhaara, 2003)

Chemical grouts can be divided into the following groups (Riekkola et al., 2002, Vgverket, 2000):

natriumsilicates acryl amid* lingnosulfates*, fenoplast and aminoplast* polyurethanes epoxy* and polyesterresines.

Currently, polyurethane or acrylic grouts are widely in use instead of the acryl amides. These are much safer for the environment, but they have to be used under control. Polyurethane-based materials expand manifold when water is introduced. Acrylics will cure to a gel. Neither of them will be as strong as cement grouts, so they must be used as a second choice and are mostly used for post-grouting fine fissures. Acrylics with an open time from a few seconds to 30 min are available on the market.

Some products, like TACSS PU foam, have very high gelling and/or expanding properties (Table 3-3), so they can be used in the case of high water leakage where cements are flushed away (Andersson, 1998). However, the water pressure in a fracture should be less than the expansion pressure of the grout. If there is a high ambient water pressure (>100 m), the early gelling is important to avoid the grout extruding after packer removal. Some problems due water pressure were experienced in the Lundby road tunnel case when using a TACSS polyurethane product for the creation of an "inner curtain" at the tunnel intrados (Bckblom, 2002).

Due the environmental and technical reasons, some of the products (marked * in the above list) have been abandoned in Sweden (Vgverket, 2000). Similar comments / reactions have been heard in the latest cases in Finland. It was an acryl amid gel RochaGil grout that was used in the Hallandssen railway tunnel site. A well-known environmental catastrophe happened there because some grout was flushed away from

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the fracture into the groundwater and poisoned nature and animals. However, RochaGil is very good material for stopping leakages with typically 98% sealing efficiency since acrylamides provide excellent penetration (Bckblom, 2002). Also in Norway, acrylamide-containing grouting agents have been abandoned 1997. But, both Banverket and Vgverket in Sweden approve polyurethane products. For example TACSS was used in the Gta Tunnel (Liljestrand, 2002).

Table 3-3. Basic properties of some chemical grouts (Vgverket, 2000; Laitinen, 2003).

Product Viscosity / expanding (times in

second)

Gelling time (min)

Stability / strength (kPa)

Silicates Dynagrout 5 mPas 1) 50-120 / 35-50 kPa Glyoxal 40 - 4-70 - Gederal Grout 10-500 mPas 15-60 / 3-4 kPa Acrylates AC-400, AP-200, TE-300 3 mPas 30 Bacteria resistant / Alcoseal (568, A, C, CS) 4 mPas 1-20 Befa Inject Q6 - 30-60 Age and freeze stabile / MEYCO MP301 + komp. 1-2 mPas 2-20 MEYCO MP307 + komp.

During the Romeriksporten railway tunnel construction in Oslo, chemical leakages from two grouting agents (polyacrylate Meyco MP 307 and polyurethane grouting agent TACSS 020/NF) were monitored (Sverdrup et al., 2000). In a 14 km and 100 m2 tunnel, water leakage was mostly at the acceptable level except at the 1.3 km section where a total flow of 1500 l/min was encountered. So TACSS foam was used for blocking macropore point-leakages, which were causing a backflow of cement into the tunnel. MEYCO was used as a second agent to stop the remaining diffusely-distributed leakage.

The possibility of a relatively large local release of chemicals into the aquatic environment was estimated, so effluent monitoring was found to be useful for risk management. In that particular case, the average leakage of acrylic acid, methacrylic acid, and 2-hydroxyethyl methacrylate were estimated be 1.2%, 0.6%, and 0.5% (w/w), respectively, of the total 62 tons of MEYCO used. The average leakage of di-n-butyl phatalate and hexadecyl dimethyl amide were estimated to be 0.16% and

out in the Finnish technology project Rock Engineering 2000 (Riekkola et al., 1996). In that report, a special chapter on TACSS grout material and its properties studied in a lab has been included.

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4. Grouting equipment The main equipment & components for grouting works are presented below. It must be noted that only a few examples are presented, and there are a number of manufacturers for each component around the world.

The grouting work starts from drilling the holes. The grout itself is mixed and agitated prior to pumping (Fig. 4.1). A hose from the pump is connected to a valve, that is, a packer, which is placed in the grouting hole. The automatic logging of the grout take has been carried out along with the grouting.

Figure 4.1. Grouting unit (http://www.atlascopco.com).

4.1 Drilling Equipment

In tunneling, the grouting holes are normally made by a drilling jumbo that can be equipped with a rod changer, so that long grouting holes can also be drilled (Fig. 4.2). The drilling rig must be capable of carrying out the appropriate grout hole pattern and drilling capacity. It must also be suitable for controlling the drilling of a defined grout fan accurately and at penetration rates appropriate to meet the cycle time requirements. The hole diameter depends on the grouting unit usually 50-65 mm, preferably 64 mm.

For pre-grouting in TBM tunnels, the drilling system can be assembled at the TBM machine (Fig. 4.3).

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Axera T 12

Atlas Copco, Rocket Boomer WL3 C

Figure 4.2. Sandvik Tamrock Axera T12 and Atlas Copco Rocket Boomer WL3 C drilling jumbos. At right, a rod changer system for the drilling jumbo.

Figure 4.3. Pre-grouting drilling system on a 3.5 m Robbins TBM (Garshol, 1999).

4.2 Platform

There are various platforms for grouting units. In the older, but still usable, systems, the grouting components are just loaded on top of the mining vessel. They might even be separate components just interlocked at the grouting site/place in the tunnel.

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The modern system is to install all the equipment permanently on easily moved vehicles like trucks (Figs. 4.4 & 4.5), in which case even multiple grouting lines can be used. Actually, increasingly often at least 2 lines with 2 pumps, preferably 3 even, are required at least if continuous pre-grouting is done. This also gives more freedom and flexibility to move inside the site or even from site to site where grouting is needed.

Figure 4.4. An Atlas Copco grouting rig with data logger at the Arlanda fast railway link project in Stockholm (www.masterbuilders.fi).

Figure 4.5. A grouting unit with three pumps at the Gjellersen site near Oslo, Norway (Photo P. Holopainen, 2001).

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4.3 Mixer

Cement and water together with additives are fed into a mixer. Several mixer types exist. Normal paddle mixers are simple to use and rather cheap. But, since the mixing results are not good enough for high quality grouting, these are not recommended for use. A turbo mixer is more suitable. A centrifugal pump circulates the grout at a high speed (1300 - 1400 rpm, max. 1435 rpm) in the turbo-mixing container and creates a shearing action between the fractions for good quality mixing. However, the best result has been obtained by using a colloidal type mixer. In the colloidal type mixer (Fig. 4.6), shear forces are also created in the mixer housing. In the Hny system, the shear forces are created by high turbulence in the casing, and, in Atlas Copcos Craelius system, the shear forces are created by close tolerance between the impeller and casing (Pettersson & Molin, 1999).

Mixing time and mixing speed are important factors influencing the grout quality. A typical mixing time for OPC is 4-5 min. The finer cements require more intense mixing. The maximum batch size is 80% of the container volume. In a colloidal mixer, the temperature might increase several degrees due to the energy release of the shear force braking. This might induce early hardening of the grout and should be controlled by the agitator (Pettersson & Molin, 1999). Also, mixer wearing should be controlled.

Figure 4.6. Left: Atlas Copcos Cemix mixer in a grouting unit in Fig. 4.5 (Photo P. Holopainen, 2001); Right: Hny HCM colloidal mixer.

4.4 Agitator

The grout should always be agitated in order to keep the grout at a low viscosity and to prevent sedimentation. The agitator (Fig. 4.7) acts as a holding tank with grout ready for grouting. In the slowly revolving agitator, the grout suspensions are homogenized and possible air bubbles removed. Its size is normally twice the size of the mixer and rotates

34

at approximate 60 rpm. There should be one agitator per pump and per grout mixture. (Pettersson & Molin, 1999; Hnys homepage http://www.haeny.com).

Figure 4.7. Left: Atlas Copcos Cemag agitator (http://www.atlascopco.com); Right: Hny HRW agitator (http://www.haeny.com).

4.5 Grout Pump

Two types of pumps for grouting dominate the market; the progressive cavity pump (pump without valves), and the valve type pump that is, piston pump (Fig. 4.8).

The pump flow and pressure capacity must be sufficient to perform a satisfying grout operation. These parameters should also be controllable and individually adjustable during grouting work. The maximum practical pressure needed in tunnel grouting is 10 MPa (100 bar). The grout flow should be high enough to avoid separation of the grout. The maximum grain size for the pump is usually varies between 3-8 mm, and should be checked prior to grouting work.

Figure 4.8. Left: Atlas Copcos PUMPAC 110B15 grout pump (http://www.atlascopco.com); Right: Hny ZMP 610 grout and mortar pump (http://www.haeny.com).

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4.6 Pressure and Flow Meters and Recorders

In many cases in Norway and Sweden, the registration unit is in the field, but back up documentation is, in most cases, still hand written. In Finland, a manual registration is always used. A new way is to use an automatic/computerized logging tool (Fig 4.9). An auto logger should be easy to use with experience of a Excel and a PC. However, the Sines gas storage case in Portugal showed that a logging system might be difficult to use by someone uneducated.

The logged parameters are typically flow, pressure, volume, time, real time, and hole number. All parameters are shown in real time and display, and stored on a PC card. It should be possible to store the logged data and easily import it to standard programs for viewing and printouts.

Figure 4.9. Left: Atlas Copcos Logac 4000 registering unit; Right: Hny HFR recording unit with inner PC software and recording system (http://www.atlascopco.com, http://www.haeny.com).

4.7 Automated Mixing and Grouting Plants

The above mentioned grouting equipment is also available as a complete unit (Fig. 4.10). There a mixer, agitator, pump and even a data logger, that is, standardized components, are individually mounted onto the container or stationary plants.

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Figure 4.10. Left: Atlas Copcos Unigrout E22H system (http://www.atlascopco.com), Right: Hny Injecto Compact IC650 http://www.haeny.com).

4.8 Packers and other accessories

Packers are used for closing-off the full length or part of a borehole if the ground has to be grouted, tested, or sealed. By closing off the hole, pressure is confined in the borehole and the fluid (water or grout) is then forced into the fissures or cracks. Closing-off is achieved by expanding a seal against the hole wall. Inside the seal, there is a tube through which the fluid is forced in and somewhere along the tube is a shut-off valve and/or a non-return valve.

Normally, the expanded seal acts as an anchor to keep the packer in the hole. Special packers with expansion shell anchors are also available.

The compression packer is tightened by mechanically expanding a rubber sleeve attached to the inner tube by turning the handle attached to the outer tube. The compression packer can be divided into two types:

reusable packers one time use or disposable packers

With disposable packers, the sleeve has a non-return valve, which can be left in the hole after the grout has hardened and the other parts can be reused (Fig. 4.11 and Appendix C). However, it should be remembered that removing the injection pipe too soon could destroy successful grouting.

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Figure 4.11. Step by step installing system for disposable packer (MBT, 2001).

Inflatable or hydraulic packers are placed in the hole by grouting pipes or drill rods and then inflated by water or air (Fig. 4.12). The inflation pressure should exceed the grouting pressure and can be achieved by a hand pump or compressed air. After grouting and grout hardening, theoretically, the inflation pressure can be lowered and the packer removed from the hole and reused. However, there have been many problems due to the packers being damaged. The hydraulic packers are also quite expensive a 0.5 meter packer costs about 400-2500 each. (Lvhaugen, 2002).

Figure 4.12. Hydraulic packers (Pettersson & Molin, 1999).

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The valves, hoses, and couplings should also taken into account when choosing suitable equipment and the pressure required for grouting work. Hoses should be as short as possible. Some pressure might disappear in long hoses and in the case of the grout jamming, short hoses are more practical.

4.9 Equipment for chemical grouting

The equipment for chemical grouting is generally similar to that in cement grouting. For some materials, like polyurethanes, slightly different equipment has been recommended (see Fig. 4.13), though the grouting idea and system are equal. The type of equipment depends on whether one- or two-component grout is used. In some very local grouting, only a hand press or hand-pumps are needed (Appendix D). In Figure 4.14, some examples of packers or plugs of 10-20 mm for fine crack chemical grouting are presented. In normal tunnel grouting using PU foam, the standard 45-63 mm packers with the 1/4 connections to the small PU pump hoses are used.

Figure 4.13. Airless Larius 3000 pumps for PU grouting (MBT, 2001).

Figure 4.14. Packers PPW1 for PU grouting in very small cracks (at left, www.deneef.fi), and Joco Composite (upper right) and Joco Wing plug for cement grouts (www.muottikolmio.fi).

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5. Grouting Design

5.1 General

Pre-investigation at the construction site is needed when planning grouting. Actually, more critical tightness requirements exist, though more detailed investigations are needed to produce good, predictable results. Experiences in Sweden and Norway show the Lundby road tunnel in Gothenburg and Baneheia in Kristiansand to be good examples, and the Hallandss and Romeriksporten railway tunnel cases as examples of extreme failure (for example,. Bckblom, 2002; Statens Vegvesen, 2001). Although in some cases investigations can be quite difficult and also expensive, they help to produce a more economical and tight cavern or tunnel. The main parameters of engineering geology (single fracture and fracture network characteristics), as well as hydrogeology (conductivity, transmissivity) of construction area, are required.

General fracture properties like spacing, length, or even aperture can be evaluated quite simply (at least to a certain degree of accuracy). But, the fracture network (boundary conditions) or fracture fillings are more complicated, and, in many cases, these play a leading role in controlling the whole grouting process.

Several analytical and numerical methods exist to estimate the groundwater leakage (for example, Cesano, 1999; Sievnen, 2001; Satola, 2001) and are occasionally used in tunnel projects. These methods (mainly based on Darcys theories) are usable, but vary considerably based on their basic assumptions, simplifications, limitations, required geological input information, as well as usability in different environments. So, the results are not completely comparable. Sievnen (2002) in her study considered Thiems approaches to shallow and imaginary wells (see Appendix A) for deep caverns to be the most relevant.

Several evaluation systems for groutability and grout spread have also been created and presented (for example, Eriksson, 2002, Hssler et al., 1992a, Hssler et al., 1992b, Hkansson et al., 1992; Satola, 2001; Sievnen, 2001). All of these are based on the rheological laws (Newtonian or Bingham fluid model) of grout, however, geological factors have been shown to play an extremely important role in grout take or groutability. Normally, the best result will be achieved if hydraulic tests, together with conventional geological site exploration, are carried out.

In Figure 5.1, a grouting procedure is presented step by step by ISRMs commission of rock grouting (1995). The main rule of thumb states that well-designed pre-grouting reduces the amount of inflow water and the need for post-grouting. Furthermore, the delay time between the grouting and excavation stages, as well as different grouting phases, must be enough for grout hardening.

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Figure 5.1. Procedure for planning and site work of grouting (ISRM, 1995).

5.2 Exploration methods for grouting need

The main aim of grouting is to reduce inflow water to a certain planned level. This can be achieved if the grout penetrates far into the rock mass, including fine fractures, and no back-flow exists.

Several geological factors and fracture properties affect the grouting work and should be defined. Cesano (1999, 2001) has presented a system of qualitative and quantitative pre-investigations in his thesis (Fig. 5.2).

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Primary condition: Geological conditions not known.

Qualitative investigations present an understanding of geological and hydrogeological information of the site.

Quantitative method presents the hydraulic conductivity of rock and possible areas for inflow water.

Mathematical methods as tools for analyzing the amount of leakage water into the cavern.

Figure 5.2. Methods to predict the amount of leakage water (Cesano, 1999).

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In qualitative investigations (Riekkola et al., 2002):

Geological factors at the site and its surroundings are evaluated (thickness of soil layers, aquifer, etc)

Fracture network of rock mass with average fractures (density, aperture, orientation),

Location, orientation, and thickness of fracture zones, and, Fracture properties of fractured zone (infillings, density, aperture, orientation).

In quantitative investigations:

Hydraulic conductivity of a rock mass and its spatial variations, Level of the water table and its spatial variations.

It is reasonable that the more open and longer fractures, or higher fracture density, are more likely to have higher inflows (Fig. 5.3). Increasing fracture density also increase grout take, and an increasing number of fractures increases grouting time. Moreover, the Swedish experience shows that horizontal fractures parallel to tunnel lines are difficult, but vertical leaking fractures are easier to define accurately. Experience, both in Finnish and Swedish cases, has shown that clay and chlorite infillings were associated with fractures with higher inflow, and on the other hand, these lead to difficulties in grouting (Sievnen & Hagros, 2002; Bckblom, 2002). The combination of filled and unfilled fractures is also difficult since flushing the filling material might create more channels due to the increase in pressure at the end of the grouting period.

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Figure 5.3. At left: The ratio of the join aperture and frequency to the hydraulic conductivity (Hoek & Bray, 1981), and, at right: Transmissivity, conductivity and flow cross-section (ISRM, 1995).

Probe drilling (10 25 m holes) and water loss or water leakage measurements are widely used to estimate the grouting need during the construction phase. However, the water inflow measurements are not very accurate since, for example, hydraulic conductivity and its variation, as well as the groundwater pressure, should be known. Small inflows are also difficult to measure during the construction phase.

The location and properties of fracture zones are very important to obtain. For example, in the Olkiluoto low and medium waste repository, which consists of 1 km of tunnels and two silos of 30 m diameter and a demonstration hall, with 2/3 of the leakage water coming from one (RiIII-RiIV) fracture zone (Sievnen & Hagros, 2002).

In the Stripa project - grouting research for a nuclear waste repository in an old mine it was found that rock could be divided in groutability classes based on their hydraulic conductivity (Pusch et al., 1985; Pll et al., 1994). Similar classes are presented for the Stockholm ring road project design (Rosengren et al., 1996). These classes are combined and presented in Table 5-1.

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Table 5-1. Groutability hydraulic conductivity relationship (Pll et al., 1994; Rosengren et al., 1996).

Hydraulic conductivity, k (m/s)

Lugeon Comments

4x10-8 < 0.3 Some close / tight fractures.

4x10-8 - 2x10-7 0.3 1.5 Only one open fracture groutable, or a few quite tight fractures, difficult to grout

2x10-7 - 7x10-7 1.5 - 5 Probably several fractures, high hydraulic conductivity, quite simple to grout

7x10-7 < 5 Open fractures, very high hydraulic conductivity (possibly a high grout consumption)

The results from the seismic methods are very seldom used for grouting design even if investigations are carried out and the results available in almost every case in Finland. Based on the research, linearity between seismic speed and hydraulic conductivity of the rock mass has been found (Fig. 5.4) - grouting may be needed if the seismic speed is less than 3,500...4,000 m/s.

Figure 5.4. Ratio of Lugeon value and seismic speed (Comit National Franais, 1964). Qc stands for Q*c /100, and c uniaxial compressive strength of rock in MPa. (Barton, 2002).

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Barton (2002) assumes that there may be a link between groutability and the Q-value. However, Dalmalm (2001) found no clear correlation in the two variable analyses between Jw - Jn - Jr- Ja values numbered according to the Q-system and the grouted volume for the different holes at Arlandabana. According to him, there are two possibilities, either there is no correlation or the correlation could not be identified with the data from this project, which could be the case when the rock mass is too homogenous. For example, the Jw value was found to be 1.0 for 99 % of the total length of 8.6 km of tunnel in. The rock quality was also quite good, while the Q-value varies from 1 to 60. According to his work, a Q-index less than approximately 5 could mean that the average grout volume would be increase (Fig. 5.5). It seems that there might be a clearer correlation between the Q-value and grout take when the rock quality is bad (Q < 5).

Figure 5.5. Average grout take in volumes plotted against the corresponding Q-value, data from 100 grout holes in app. 3 fans (Dalmalm, 2001).

A modified Q for grouting (Qi) was implemented in 1991 by Johansen et al. (Fig. 5.6). The modified equation has the same base of classification as the Q system except for the Lugeon number:

46

+

=Lug

JaJrJn

RQDQi 11

Figure 5.6. The relation between grout takes (kg/tunnel-m) and the Qi-value. The limit curves are from two tunnels in Norway (Johansen et al., 1991).

Dalmalm (2001) in his thesis finds a correlation between the Lugeon value and the amount of grouted cement (Fig. 5.7).

Figure 5.7. The Lugeon sum and grouted cement amount (kg/drill meter) for the 8 fan halves with representative trial results (Dalmalm, 2001; Dalmalm & Janson, 2001).

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5.2.1 Working methods

Rock or tunnel grouting is carried out prior to blasting, i.e. pre-grouting, or after blasting as post-grouting. The size of the project, as well as environmental & tightness requirements, determine which is used. Pre-grouting is mainly used (Fig. 5.8). Failed and still dripping sections identified after blasting are repaired by post-grouting, thus, a combination of both methods is mainly used. The main ideas and advantages or disadvantages of pre- and post-grouting are discussed in Appendix E.

Pre-grouting, single cover (3-4 blast rounds per grouting round)

Pre-grouting, double cover (always overlapping of 1-1.5 * blasting round)

Post grouting, curtain grouting at the dripping places.

Combinations of cover grouting and post grouting.

Figure 5.8. The most typical cases in pre- and post-grouting, and a combination of the two (Pettersson & Molin, 1999).

5.2.2 Drill pattern design and grouting order

The number, length, and spacing of holes in a grouting fan vary from case to case. It usually depends on the size and location of the tunnel, stated requirements for tightness, and/ or environmental safety and geology. Typically 10 - 30 holes with a length of 15 - 30 m (2-4 times blasting round) and spacing 1 - 3 m is used (see Fig. 5.9 upper). Shorter holes can also be used in bad rock conditions.

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Tightness class 1: Requirement: 0.51.0 l/min/100 m, Systematic grouting: 66 holes, 10...13 m Hole spacing 1 m

Tightness class 2: Requirement: 2.0 l/min/100 m Systematic grouting: 44 holes, 13 m Hole spacing 2 m at roof and 1 m at floor.

Tightness class 3: Requirement: 2.5 l/min/100 m Systematic grouting: 30 holes 17 m Hole spacing 2 m

Figure 5.9 Grouting drill pattern (upper) and an example of grouting classes used in the Lundby tunnel, Sweden (MBT, 2001; Statens Vegvesen, 2001).

If the aim is just to prevent the tunnel from dripping water, grouting the roof and walls (some cases just the roof) can be enough. If the groundwater level should not sink, the floor/bottom of the tunnel should also normally be grouted. In many cases 2/3 of the water leakage comes from the floor and it is difficult to see due to the dirt remaining on

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the tunnel bottom (Roald, 2002). In some cases, the tunnel face may also need grouting to prevent a lowering of the groundwater level and to reduce problems during drilling and charging at least, in the face grouting of bad rock quality drifts.

In some cases like the Botniabanan railway link in eastern Sweden and the Lundby road tunnel in Gothenburg, tunnels are divided into three grouting classes depending on the rock type (Botniabanan, 2000; Vaaranta, 2002; Statens Vegvesen, 2001). The number of boreholes in the Lundby tunnel is very high (Fig. 5.9), since extremely tight requirements of 0.5 - 2.5 l/min/100 m for that under-city tunnel were set. At Storhaugtunnel in Stavanger, pre-grouting was also done by using 30 - 72 hole/grouting round at 85 m2 tunnel (typically 62 holes) due to problems with the clay-filled joints that were opened by flushing (Statens Vegvesen, 2001).

The orientation and inclination of holes, that is, spacing of holes at the end of the fan, should be carefully planned and controlled at the site based on the geological surroundings. Nowadays in Sweden, control measurements for borehole orientation are taken. For example, at the Lundby tunnel about 20% of holes were measured by using an inclinometer with a permitted maximum deviation of 3 - 5% (Statens Vegvesen, 2001) At the Botniabanan railway link, the orientation of the grouting holes was also measured and the acceptance limit for a 27 m hole was 3.5 % (Vaaranta, 2002).

Drilling should be planned in such a way that the grout is everywhere raised above the designed rock bolting section. That is done to avoid bolt hole penetration to the non-grouted zone and opening new channels for leaking water. If pre-grouting is also performed in a high stress environment, it could be effective to the extended grouted zone beyond the zone where the rock mass strength is exceeded. This distance can be evaluated based on the ratio of the rock stress and strength of a rock mass.

To extend the grouted zone to an adequate distance from the tunnel, the drilling fans should overlap normally from 1/3 to of the grout hole length. In Norway, about 9 m overlap is used (Roald, 2002). This allows the drilling of the next round to be started directly after grouting work. After the first blasting round, the overlap is still about 4 m and the grout has time to harden during the drilling, charging, and hauling of the following round.

The best way to drill and plan grouting holes is to use drilling jumbo together with its own software and the registration system. During drilling, the user should write his observations in the drilling report, like:

penetration changes and if the anti-jamming automatic is activated, possible loss of the drilling water, color of the drilling water, opinion of the rock quality based on his experience.

Grouting holes should be flushed after drilling. That is typically done by using the drilling jumbos flushing water. However, special devices with high pressure are

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recommended and even required for use. One effective way is to use equipment that is designed to flush sewers.

There are several systems and ideologies concerning the order of the grouting. One could start grouting in the bottom corner of the tunnel and continue around the pattern in order, which is the typical way in Finland. In Sweden, water loss measurements are carried out in each hole and grouting starts with the holes with highest inflow and continued with the next highest inflow amount and so on. This was the case, for example, in the Botniabanan tunnels. In Norway, the most used method is to start from the bottom holes and come up toward to the center roof hole (Hognestad, 2002; Roald, 2002). Holes can be grouted one by one or in pairs depending on the number of grouting units. However, in complicated rock, holes should be grouted one by one despite the time lost in the project.

In bad rock condition or if the roof cover is thin, an outer zone can be grouted before actual pre-grouting (Fig. 5.10). That procedure reduces the loss of grout and allows higher pressures to be used.

Figure 5.10. Pre-grouting in bad rock quality with an umbrella (Hansen et al., 2002).

Smooth (cautious) blasting at the area where grouting will be or has been performed might be needed to create minimum disturbance, which is actually, more important for grouting at the tunnel floor. However, not all experts agree, but experiences from Lundby and Sdra Lnken road tunnels in Sweden are encouraging (Bckblom, 2002).

A typical grouting procedure made by a contractor is shown in Appendix F.

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5.2.3 Recipes and grouting speed

In Finland, grouting is normally started with a high w/c-ratio being 1-3 depending on the use of plasticizers. If the grout pressure does not increase and the grout take is some 50 kg / bore hole meter, the w/c ratio is decreased. Further, the w/c is changed until the desired maximum grouting pressure can be reached, but normally not more than w/c 0.5. That criterion was followed in the case of Salmisaari coal storage and Isokyl tunnel on Highway VT1. Some recipes used at Salmisaari coal storage construction site are presented in Appendix G.

The situation is very similar in Norway, where in some cases one mix of lean grout (w/c ~2.0) is pumped first to grease the hose and rock (Statens Vegvesen, 2001). Such a high w/c can be used if stable grout is used, but it is, however, very much site dependent (Roald, 2002). As an example, at the Lunner Gardemoen road tunnel in Ra grouting was started with w/c 2 till for 120 liters (one batch) and then changed to 1.3/1.1 for 3000 4000 l/ hole, and finally to 0.55. Ultrafine cement with a maximum grain size of 12 m was required (Lvhaugen, 2002). Since there is no consensus on this issue, there is also another example, such as the Jong-Asker railway tunnel where grouting was started using a w/c 1.1 for 300 kg and then changing to 0.9 or 0.7 and further to 0.5 (Rongmo, 2002).

At Botniabanan, a starting grout mix was chosen based on the water loss measurements; in the case of Lugeon < 1 => w/c 2, and if Lugeon > 1 => w/c 1 were chosen. The starting mix was used for about 250 kg and then changed to 0.8 for about 450 kg and further to ending mix of 0.5. Injektering 30 cement together with plasticizers (0.65 or 1 %) was used based on the stated requirements by the owner (Botniabanan, 2000; Vaaranta, 2002). Dry holes were filled using w/c 0.5, and, grouting holes were plugged using w/c 0.3.

Usually the maximum grouting speed used at the beginning is 20 l/min. There are several opinions concerning the right value. In Norway, the grouting speed is defined in the field, but based on the equipment capacity; in some cases, a pressure capacity of 100 bar and grouting speed of 60 l/min is required (Nomeland et al., 2002). Depending on the situation, 1 to 3 holes are grouted simultaneously.

5.2.4 Grouting Pressure

Grouting pressure has been a difficult issue among the experts. Divided opinions and two groups exist: opinions against and for high pressure. The first group firmly believes that increasing the grouting pressure decreases work safety and breaks the rock mass by creating new fractures and opening existing ones. The latter group of experts state that the increase in the pressures used is needed for better grout penetrability to create more dry tunnels, and, that no extra damage to the tunnel, or lessening of work safety, is encountered. The highest pressures used in Finland are about 3 - 4 MPa, but typically just 0.5 2 MPa is used (see Appendix B).

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ISRMs grouting commission has stated in their final report (1995) that since the grout flow is dependent on the nature of the joint to be filled, the flow properties of grout, and the effective pressure in the joint, it is logical to use as high a grouting pressure as can be permitted. This results in the grout permeating a greater distance, hence, reducing the need for frequent re-siting of the equipment, and reducing the cost of the operation.

In Norway, where much grouting is carried out in difficult and sensitive areas as high as 8 to 9 MPa (8090 bar) has been used without any serious problems or damages even close to the surface (Roald, 2002). For example, in a railway tunnel between Jong and Asker near Oslo, a pressure of 6 MPa was mainly used, but the maximum pressure of 10 MPa was stated in the grouting instructions, with the rock overburden varying from 20-40 m (Rongmo, 2002). A 10 MPa pressure for grouting equipment is also required. High pressure is needed if the fractures are tight and very low leakage is allowed into the cavern. Usually, the main problems in the case of high grouting pressures are the capacity of the grouting equipment (typically max. pressure for pumps are 10 MPa) and the packer or host installations. At the Lunner Gardemoen road tunnel through the hill with 0-350 m overburden, a pressure of 6 - 9 MPa is used with no damage due to the high grouting pressure (Lvhaugen, 2002).

Sweden wants to limit pressures as in Finland. However, no disadvantages in Hallandss or the Arlanda fast railway link project were found when using high over pressures like 5 MPa (Bckblom, 2002).

A criterion for the maximum allowed pressure is not necessarily the depth of the tunnel (rock weight). In tight fractures, the pressure losses are significant so the influence area, and furthermore the effective force, stay very limited. The Situation is the reverse in the case of very open fractures where in extreme case the rocks weight should not be exceeded. One rule of thumb states, as does the theoretical point of view, that grouting pressure must exceed twice the groundwater pressure to gain a good result and prevent fingering of the grout. Another rule from Norway is that the pressure should be 2.5 - 3.5 MPa higher than the groundwater pressure. Hytti (1981) presented one way to estimate a suitable grouting pressure for different rock qualities at certain depths (Fig. 5.11). A similar evaluation system is also presented in ISRM (1995). There it is also states that the grouting pressure applied in China is twice as high as those of the European rule of thumb are (Fig. 5.11) with no detrimental effects.

Usually grouting is carried out using static pressure. In some specific areas where very high sealing efficiency is required, such as a repository for nuclear waste, dynamic pressure might be usable in grouting and has been researched (Pusch et al., 1985; Riekkola et al., 1996).

In dynamic grouting, both static and dynamic pressure is used. First the grout is pumped into the hole under steady pressure and a vibration is simultaneously carried out using, for example, percussion drilling machine. The vibration will induce shear waves, which reduces the friction between cement particles and increases penetrability (Pll et al., 1994).

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a)

b)

Figure 5.11. a) Estimation of grouting pressure: 1. Weak rock domain, 2. Good quality rock domain, 3. European rule: 1 bar/overburden-m (Hytti, 1981), b) A state of flow around a borehole (ISRM, 1995).

The dynamic grouting has been tested in the Stripa mine project researching a suitable tool for very fine fracture grouting (Pusch et al., 1985). Static pressures in the field test were 1.1 - 3.3 MPa, dynamic pressure 2.5 - 3.5 MPa, and initial vibration 50 Hz. The vibrations in the grout were measured at 20 - 200 Hz, but that rapidly decreases when grout enters the hole.

With this method, both clay and cement suspensions were able to penetrate dozens of centimeters into the fracture with a 0.10.2 mm aperture. So, dynamic grouting might be needed in the future when very low leakage is allowed in an already tight rock mass, for example, when a repository for nuclear waste will be constructed. Actually, some tests by Posiva have recently been carried out (Riekkola et al., 2002).

5.2.5 Controlling grouting and stop criteria

The grouting pressure and/or amount of grout are used as control parameters to stop the grouting work. The limits for these parameters should be decided prior to grouting work and continuously checked, preferably by an automatic logging system (see Chapter 4).

An increase in grouting pressure during pumping indicates tight fractures at least with the w/c-ratio used. In some cases, increasing the w/c-ratio might still be required for a satisfactory final product.

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Another signal to stop grouting or change the recipe is a grout take; if the grout take is high and the pressure does not increase, a joint does not get filled, and a smaller w/c-ratio should be used until the pressure increases. High grout-take in volume might also be due to a grout leak to the ground surface or back to the tunnel. For example, a maximum grout take while normal grout mix is used could be about 50 kg of cement/drill-m or 100 l of grout/drill-m.

Normally, the stop criteria for grouting is that the grouting is completed when the set maximum amount of grout has been reached, or the apparent grout take is less than 0-3 l/min at maximum pressure. Maximum pressure must be maintained for at least 2 - 5 minutes. If the permitted leakages are very low, it may be necessary to increase the time to maintain maximum pressure (Fig. 5.12) or to just set the grout take at zero. Some believe that 2 - 5 min is enough.

Figure 5.12. Volume increases during time in minutes. Data is from the grouting trials at South Link project in Stockholm (Dalmalm, 2001).

Some recent examples for stopping criteria:

Lunner Gardemoen road tunnel at Ra, Norway: grout take 0 and pressure of 60 bar for 1 min; max grout take 4000 kg/hole (Lvhaugen, 2002),

Jong-Asker railway tunnel, Oslo: grout take 0 and pressure of 60 bar for 5 min (Rongmo, 2002),

Botniabanan, rnskldsvik, Sweden: grout take < 2 l/min for 5 min with 25 bar overpressure (Vaaranta, 2002),

Sines gas storage, Portugal (Lemminkinen Construction): see Appendix F.

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A Grouting Intensity Number (GIN), presented by Lombardi & Deere (1993), uses a combination of pressure and grout take in a more quantitative way:

GIN = p*V ,

Where p = grouting pressure at zero grout take

V = grout volume at zero grout flow

Grouting continues if p < pmax or V < Vmax. For example, in the case of Hallandss (Bckblom, 2002) the suggested values were; pmax = 55 bar (5.5 MPa), Vmax = 25 kg/m, and, GIN = 275340. However, the GIN method is difficult to use in situ, since the grout take is so dependent on geology (Pettersson, 2003; Hognestad, 2002, Roald, 2002).

Special attention should be paid to the grouting time that should always be controlled. If the grouting lasts too long, it might start to set, so equipment might be needed to empty and clean.

5.2.6 Post-grouting

Post- grouting is a method that is used to grout behind the face in an already excavated part. It is said to be a passive approach. The need for post-grouting depends on the apparent leakage amount into the tunnel and on the initial requirements. The lengths of the grouting holes are shorter and spacing denser than in pre-grouting, since grouting targets are very local. Typically, post-grouting must be focused to the fracture zones, bad rock quality areas, or areas that are disturbed / damaged due to the blasting.

It is much more expensive to stop the water by post-grouting than by pre-grouting. Post grouting might be even 310 times more expensive (a value of 20-50 was given on MBTs homepage), which has been proven in many projects. So, post-grouting should always be a repair or second stage strategy and in addition to pre-grouting.

In principal, the same idea as presented in Figure 5.10 can be used to reduce grout leakage to the tunnel during post-grouting (Fig. 5.13).

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Figure 5.13. Inner curtain (umbrella) principles for post-grouting technique (from Elkems course material).

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6. Quality and compliance control

6.1 Quality control of grouts

Based on the European Standards for grouting (SFS-EN 12715), the properties and usability of planned and selected grout recipes should be tested and controlled, as well as reported, before grouting work. Standardized testing methods (equipment, boundary conditions, and analysis) should be employed to allow comparison of the characteristics of the products provided by different suppliers. Control should be continued during the project with specified methods and system selected beforehand. The typical controlled parameters and the tests used prior to the grouting work are:

compressive strength, density by a mud balance system (Fig. 3.10) to control grout mixing, shrinkage, penetrability, sand column test (see Fig. 3.7), NES, filter test, outflow time, (Cone viscosity), Marsh cone test (see Fig. 3.11a), bleeding rate, sedimentation, setting time, Vicat test.

If the conditions on site differ substantially from the laboratory conditions the test (especially the temperature test) should be conducted under in situ conditions. The temperature development during testing should be monitored (SFS-EN 12715).

During the construction phase, at least the following tests should be done and reported (SFS-EN 12715):

density (Fig. 3.10) both suspensions and microfine suspensions, Marsh viscosity (Fig. 3.11a) both suspensions and microfine suspensions, bleeding, (Fig. 3.11b) both suspensions and microfine suspensions, setting time suspensions grain size / sand column test (see Fig. 3.7) - microfine suspensions.

Depending on the recipe in laboratory (+20C), the setting of the grout should start about 1 hour after mixing and end within 8 hours. At the site, the setting can be checked by the cup-test. When a pen does not penetrate the grout, setting has started and when the grout does not flow out from the cup setting has stopped. Of course, this method is not accurate but suitable for site conditions.

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In Finland and Sweden, the control procedure is more or less like that presented above. In Norway, no tests have been carried out during grouting work, since the manufacturers' tests are usually accepted.

6.2 Control of grouting procedure

The whole grouting procedure, from drilling to each grout batch and personnel, should be reported including the following information:

grouting place (drifts name and pole), hole definitions number, length, orientation, deviation, diameter prescription of the grouting unit, packer type and installation depth, grout used in each of batch, grouting time and grout consumption per hole, maximum pressure in each hole, personnel.

6.3 Acceptability control and actions due to unaccepted quality

The most essential factor for controlling inflow is the hydraulic conductivity of the grouted zone; thus, how successfully grouting has been carried out. In general, the tunnel area or diameter and the initial hydraulic conductivity of the rock mass are far less significant for inflow (Bckblom, 2002). Furthermore, it is straightforward that the thickness of the grouted zone has an effect in the long term. For a successful final product the installed rock bolts or other connections should never penetrate through the grouted zone and destroy the sealing.

A dry tunnel is the best proof of successful grouting. However, the grouted zone should be tested during the construction phase by drilling a few control holes not longer than the grouted zone - and measure the leakage or water loss. If the measured value is higher than the planned maximum leaking, the grouting should be repeated partly or wholly. That procedure should be decided and planned prior to the contract so that all the parties are well informed. That is the custom nowadays in most Swedish and Norwegian tunnel contracts.

Another way for leakage control is to install measuring weirs (Fig. 6.1) for all or certain parts of the tunnel - for example, every 100 200 m. In some projects only a total inflow has been limited and measured by using such weirs. However, there are cases

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were most of the tunnel is dry, but one or two sections have a major inflow. But if the total inflow stays under the required limit, the project might be accepted and the water is controlled by a drainage system. That might be the wrong decision in the long run. It should be remembered that running water might flush fracture fillings and induce instability in the tunnel surroundings. There might also be environmental problems in the surface of the ground.

Figure 6.1. Example of measuring weir (Pettersson & Molin, 1999).

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7. Purchase methods

Typically, in a contract between client and contractor, grouting is divided into the following divisions:

Investigations: probe-holes price / hole meter