Table Of ContentSHOTCRETE: ELEMENTS OF A SYSTEM
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PROCEEDINGS OF THE THIRD INTERNATIONAL CONFERENCE ON ENGINEERING
DEVELOPMENTS IN SHOTCRETE, QUEENSTOWN, NEW ZEALAND, 15–17 MARCH 2010
Shotcrete: Elements of a System
Editor
Erik Stefan Bernard
TSE Pty. Ltd., Sydney, Australia
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Shotcrete: Elements of a System – Bernard (ed)
© 2010 Taylor & Francis Group, London, ISBN 978-0-415-47589-1
Table of contents
Preface VII
Acknowledgements IX
A comparison of models for shotcrete in dynamically loaded rock tunnels 1
L. Ahmed & A. Ansell
Structural behaviour of shotcrete on irregular hard rock surfaces 11
A. Ansell
Crack widths in ASTM C-1550 panels 21
E.S. Bernard & G.G. Xu
Precision of the ASTM C1550 panel test and field variation in measured FRS performance 29
E.S. Bernard, G.G. Xu & N.J. Carino
Influence of the number of replicates in a batch on apparent variability in FRC and FRS
performance assessed using ASTM C1550 panels 39
E.S. Bernard, G.G. Xu & N.J. Carino
Round and square panel tests—effect of friction 49
Ø. Bjøntegaard
Evaluating the service life of shotcrete 57
L.-S. Bolduc, M. Jolin & B. Bissonnette
The use of shear wave velocity for assessing strength development
in Fibre Reinforced Shotcrete 65
D. Ciancio & M. Helinski
Shotcrete tunnel linings with steel ribs: Stress redistribution due to creep and shrinkage effects 71
T. Collotta, G. Barbieri & M. Mapelli
Economical mix design enhancements for FRS 85
S.B. Duffield, U. Singh & E.S. Bernard
Advances in shotcrete education and nozzleman certification in America 99
J.-F. Dufour & M. Jolin
Robotic shotcrete shaft lining—a new approach 105
K. Ford, L. Spence, D. McGarva & M. Calderwood
Advances in shotcrete impact-echo testing 111
A. Gibson
The influence of air content on sprayed concrete quality and sprayability in a civil tunnel 119
C.J. Hauck & G. Malm Kristiansen
Shotcrete as a good looking final finish—it is possible! 125
M. Hicks
V
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Shotcrete research and practice in Sweden—development over 35 years 135
B.J. Holmgren
Design and construction of a permanent shotcrete lining—The A3 Hindhead Project, UK 143
T.J. Ireland & S. Stephenson
Shotcrete with blended cement and calcium aluminate based powder accelerator
for improved durability 153
A. Ishida, M. Iwasaki & A. Araki
Sprayable fire-protective layers in traffic tunnels 159
W.A. Kusterle
Shrinkage and durability of shotcrete 173
B. Lagerblad, L. Fjällberg & C. Vogt
The use of geotechnical photogrammetry in underground mine development 181
J.L. Lett & J. Emmi
Testing of unreinforced masonry walls seismically retrofitted with ECC shotcrete 191
Y. Lin, J.M. Ingham & D. Lawley
Sprayed concrete nozzle operator training and certification 201
A. Loncaric, C. Larive & D.R. Morgan
The use of Fibre Reinforced Shotcrete at Cadia Hill Open Pit 209
R.J. Lowther
Structural Shotcrete in Western Canada 213
D.R. Morgan
Centrifugal placed concrete for lining horizontal pipes, culverts, and vertical shafts 225
D.R. Morgan, K. Loevlie, N. Kwong & A. Chan
Round and square panel tests—a comparative study 233
S.A. Myren & Ø. Bjøntegaard
Shotcrete application on the Boggo Road Busway driven tunnel 243
E.J. Nye & D. Alt
Use of calorimetry to select materials for shotcrete 255
P.J. Sandberg & W. Walsh
Factors to consider in using PP fibres in concrete to provide explosive spalling
resistance in the event of a fire 261
K. Smith & T. Atkinson
Composite linings: ground support and waterproofing through the use
of a fully bonded membrane 269
C.A. Verani & W. Aldrian
Shotcrete application and optimization at PT Freeport Indonesia’s Deep Ore Zone mine 283
E. Widijanto, E. Setiawan, M. Ramirez & D. Napitupulu
Air void structures in blended-cement wet-mix shotcrete 291
K.-K. Yun, S.-Y. Choi, J.-Y. Seo, B.-S. Jung & C.-K. Jeon
Author index 299
VI
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Shotcrete: Elements of a System – Bernard (ed)
© 2010 Taylor & Francis Group, London, ISBN 978-0-415-47589-1
Preface
The Third International Conference on Engineering Developments in Shotcrete has been organized by
the Australian Shotcrete Society to encourage discussion about on-going development of shotcrete tech-
nology within the construction and mining industries, and disseminate recent information concerning
advances in this field. It was held in Queenstown, New Zealand, with the financial support of companies
involved in the shotcrete industry both within the Australia/New Zealand area, and the wider world.
Planning and preparation for the conference was strongly guided by the organizing committee within the
Australian Shotcrete Society, particularly Tony Cooper and John Brown. The American Shotcrete Asso-
ciation also assisted in promoting the conference, for which the society is indebted.
Use of shotcrete for ground support and other applications continues to increase internationally. The
reasons for this include an increase in awareness among engineers and contractors, particularly in devel-
oping countries, of the possibilities and economies that this process of concrete placement offers. The
underground mining industry in Australia is at the forefront of implementation of new shotcrete technol-
ogies, with almost universal adoption of Fibre Reinforced Shotcrete for ground support. For this reason
many of the papers included in this volume are based on practices within this industry. The more con-
servative attitudes prevalent in other countries, and in the civil tunneling industry in general, have resulted
in a slower rate of uptake of recent innovations. Some of these innovations were reported at the first and
second conferences in this series, held in Hobart in 2001, and Cairns in 2004, as well as at the two long
standing series of conferences on shotcrete held by the Norwegian Concrete Association and Engineering
Conferences International. Developments and innovations related to shotcrete have arisen in many parts
of the world in recent years and this is evident in the diversity of authors represented at this conference.
Each paper presented herein was independently and anonymously reviewed by up to three peers from
within the industry. The process of review was lengthy and rigorous, and I would like to extend my thanks
to the reviewers for their assistance in making this conference possible. I would also like to thank the spon-
sors for providing such generous support and thereby contributing to a rewarding conference experience
for the delegates.
E.S. Bernard
Conference Chairman and Editor
VII
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Shotcrete: Elements of a System – Bernard (ed)
© 2010 Taylor & Francis Group, London, ISBN 978-0-415-47589-1
Acknowledgements
A successful conference requires the involvement of a large number of people. The organizing committee
would like to thank the following individuals and companies for their support in making this confer-
ence possible. In particular, the committee would like to thank Vickie Hill, of Queenstown Destination
Management, for the day-to-day preparations leading up to the conference and organization of delegate
registration within Queenstown.
Sponsorship has been provided by
Elasto-plastic Concrete P/L (Principal sponsor)
BASF (Australia) P/L
Jetcrete Australia P/L
Stratacrete P/L
The Rix Group P/L
The papers were reviewed by
Alvarez, R. PUC, Chile
Ansell, A. KTH, Sweden
Asche, H. Aurecon, New Zealand
Bernard, E.S. TSE P/L, Australia
Clements, M. Grenz P/L, Australia
Diederichs, M. Queens University, Canada
Duffield, S. Newcrest Mining Ltd, Australia
Garshol, K. BASF, USA
Grimstad, E. NGI, Norway
Holmgren, J. KTH, Sweden
Hauke, C. Veidekke, Norway
Ishida, A. Denka Chemicals, Japan
Kusterle, W. HS Regensburg, Germany
Jolin, M. Laval University, Canada
Morgan, D.R. AMEC Earth & Environmental, Canada
Potvin, Y. UWA, Australia
Rieder, K.-A. W.R. Grace, Germany
Tatnall, P. Consultant, USA
Van sint jan, M. PUC, Chile
Wood, D. Consultant, Canada
IX
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Shotcrete: Elements of a System – Bernard (ed)
© 2010 Taylor & Francis Group, London, ISBN 978-0-415-47589-1
A comparison of models for shotcrete in dynamically
loaded rock tunnels
L. Ahmed & A. Ansell
Royal Institute of Technology, Stockholm, Sweden
ABSTRACT: During blasting in tunnels and mines, the shotcrete-rock interaction is influenced by
propagating stress waves. Shotcrete support in hard rock tunnels is here studied through numerical analy-
sis and comparisons with previous numerical results, measurements and observations in situ. The stress
response in the shotcrete closest to the rock when exposed to P-waves striking perpendicularly to the
shotcrete-rock interface is simulated. The first model tested is an elastic stress wave model, which is one-
dimensional with the shotcrete assumed linearly elastic. The second is a structural dynamic model that
consists of masses and spring elements. The third model is a finite element model implemented using the
Abaqus/Explicit program. Two methods are used for the application of incident disturbing stress waves:
as boundary conditions and as inertia loads. Results from these three types of models are compared and
evaluated as a first step before a future extension to more detailed analyses using 3D models.
1 INTRODUCTION can take place. It involves development of sophis-
ticated dynamic finite element (FE) models which
The main design principle for rock support is to will be evaluated and refined through comparisons
help the rock carry its inherent loads. The rock between calculated and measured data. At first,
support is generally designed for static loading existing simple prototype models will be evaluated
conditions but in many cases, however, the open- through calculations and comparisons with exist-
ings are also subjected to dynamic loads. One ing data. The models will then be further refined
example is rock bursts that can cause serious dam- and re-modelled using FE programs and in the fol-
age to underground structures. Another source of lowing step the prototype models will be replaced
dynamic loads is detonation of explosives during by a model based on solid FE elements. Non-linear
excavations of tunnels and underground spaces. material properties will be introduced, replacing
These detonations give rise to stress waves that the initial, elastic approach. The model will be used
transport energy through the rock and these may, to study real in situ cases with realistic and complex
depending on the magnitude of the waves, cause geometry, such as shotcrete on tunnel walls and
severe damage to permanent installations and sup- ceilings behind a tunnel front where blasting takes
port systems within the rock, such as shotcrete. place. The results will lead to the establishment of
In tunnelling, the search for a more time-efficient recommendations and guidelines for practical use
construction process naturally focuses on the pos- in e.g. civil engineering underground work, tunnel-
sibilities of reducing the time periods of waiting ling and mining. This paper presents preliminary
between stages of construction. As an example, the results, ongoing and future research within the
driving of two parallel tunnels requires coordina- project, assuming fully hardened shotcrete.
tion between the two excavations so that blasting
in one tunnel does not, through vibrations, dam-
age temporary support systems in the other tunnel 2 SHOTCRETE AND BLASTING
prior to installation of a sturdier, permanent sup-
port. There also arise similar problems in mining. There are few published reports and papers on tests
To be able to excavate as much ore volume as pos- conducted in tunnels and mines where shotcrete has
sible, the grid of drifts in a modern mine is dense. been subjected to vibrations from large-scale blast-
This means that supporting systems in one drift ing. Due to the lack of knowledge, unnecessarily
are likely to be affected by vibrations in a neigh- strict guidelines for acceptable vibration levels from
bouring drift. blasting close to hardened as well as newly sprayed
This research project was initiated to study how shotcrete are often used. For safe underground con-
close in time and distance to shotcrete safe blasting struction work, this leads to longer production times
1
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and higher costs. The guidelines often contain of the explosives Q and the constants a and β.
1
allowed vibration velocities, expressed as peak par- Equation (1) is valid only for situations where R
ticle velocities (ppv), which are difficult to trans- is large compared to the length of the explosive
late into minimum distance and shotcrete age. In charge, thus assuming a concentration of the
the following a short description of stress waves explosive charges. As previously mentioned v of
max
in rock is given, followed by a summary of earlier an incoming wave will be doubled when reflected
interesting experiences and research on vibration at the free surface of, for example, a tunnel, and
resistance of shotcrete. therefore must be obtained from Equation (1)
through multiplication by two (Ansell 1999).
The time-dependent stress from a propagating
2.1 Stress waves in rock longitudinal wave is
Detonations in rock give rise to stress waves that
transport energy through the rock, towards pos- σ(t)=ρrockcrockv(t) (2)
sible free rock surfaces. Wave motion can be
described as movement of energy through a mate- where ρ is the rock density and v(t) the particle
rial, transportation of energy achieved by particles rock
velocity. The wave propagation velocity in elastic
translating and returning to equilibrium after the
materials is
wave has passed (Bodare 1997). The propagation
velocity is governed by the type of rock and is dif-
ferent for different types of waves, such as compres- c = Erock (3)
sion waves (P-waves) and shear waves (S-waves). rock ρ
rock
The P-wave propagates faster than the S-wave and
is therefore the first to reach an observation point
where E is the elastic modulus of the rock mate-
when both wave types have been generated simul- rock
rial. It should be noted that the allowable dynamic
taneously at a distant source, e.g. an earthquake
load on a structural system also depends on the
or a blast round. There are also other types such
frequency content, ie. higher ppv levels can be
as Rayleigh waves that appear on surfaces, see e.g.
accepted for high frequencies. The highest frequen-
Dowding (1996).
cies are however filtered out as the waves propa-
As each wave passes, the motion of the particles
gate through the rock.
in the rock can be described in three dimensions,
either as displacements, velocities or accelerations.
When a wave-front reflects at a free surface, such 2.2 Dynamic load capacity
as that of a tunnel, the particle velocities are dou-
A couple of interesting reports present in situ tests
bled and the stresses are zero over the surface. This
conducted in tunnels and mines where fully hard-
means that a compressive wave reflects backwards
ened shotcrete on rock have been subjected to blast
as a tensile wave, etc. Shotcrete sprayed on rock
induced vibrations. Kendorski et al. (1973) carried
exposed to blasting will thus be affected by incom-
out in situ tests to determine how a shotcrete lin-
ing stress waves that reflect at the shotcrete-rock
ing was affected by standard drift blasts at various
interface. When exposed to incoming stress waves,
distances from the lining. A standard blast that
the inertia forces caused by the accelerations acting
consisted of 409 kg premixed ammonium and fuel
on the shotcrete give rise to stresses at the shot-
oil (ANFO) showed that there was no bond failure
crete-rock interface which may cause adhesive fail-
ure. It is also possible that the shotcrete may fail at the shotcrete–rock interface. The tests revealed
that cracks started to appear in the shotcrete when
due to low tensile strength. The particle velocities
the detonations occurred at a distance of 16.5 m
that can be measured remote from a detonation
and that the function of the lining was consider-
in rock will show a decrease in magnitude with
ably reduced when detonating from 12.2 m. No
increasing distance to the source of explosion. This
vibration levels were recorded during these tests.
decay is caused by geometrical spreading and hys-
McCreath et al. (1994), Tannant & McDowell
teretic damping in the rock (Dowding 1996) and is
(1993), and Wood & Tannant (1994) presented
governed by a relation of the form
results from tests carried out in a Canadian gold-
mine where steel fibre-reinforced and steel mesh-
−β
⎛ R ⎞ reinforced shotcrete linings were subjected to
vmax =a1⎝⎜ Q⎠⎟ (1) vibrations from explosions. During the tests, it
was found that steel fibre-reinforced shotcrete can
maintain its functionality even though exposed to
where v is the peak particle velocity (ppv) at a vibration levels of 1500–2000 mm/s. It was seen
max
distance R from the point charge with the weight that mesh-reinforced shotcrete performs better
2
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than steel fibre-reinforced shotcrete under very presented as a relationship between panel damage,
severe dynamic loading conditions. This is due to its energy dissipation and displacement.
ability to retain broken rock even when extensively
cracked, which is not the case with fibre-reinforced
shotcrete. It is reported that the shotcrete linings 3 PRELIMINARY RESULTS
were partially cracked and that no shotcrete slabs
were displaced or ejected by the blasting, nor was As a continuation to the research described in the
any significant increase in drumminess found by previous section in situ tests with small and larger
manual hammer sounding as the blasting contin- scale detonations were conducted, followed by
ued. The latter indicates that the shotcrete–rock numerical modelling (Ansell 1999, 2004a, 2004b,
adhesive bond was undamaged. Further, it is sug- 2005, 2007). These results are briefly summarized
gested that mesh-reinforced shotcrete may remain and commented on in the following.
partially functional when subjected to particle
velocities as high as 2000–6000 mm/s (McCreath
3.1 In situ tests
et al. 1994). These conclusions were based on
empirical observations by the ground control staff Tests on young shotcrete were performed on site
at operating mines in the Sudbury area (Ontario, in the Kiirunavaara iron-ore mine, situated in the
Canada). north of Sweden (Ansell 1999, 2004a). The test
The function of shotcrete in the support of burst sites were situated on both sides of a tunnel that
prone ground has further been investigated through was not originally reinforced by shotcrete. A total
static and dynamic testing of shotcrete panels by of four tests were carried out, each performed with
Beauchamp (1995), also presented by Tannant a unique type of explosive charge not repeated in
et al. (1995, 1996). In their test program, impacts any of the other tests. Two shotcrete areas of vary-
of rock blocks ejected from medium-sized rock ing age, one young and one very young, were sub-
bursts were simulated by using weights dropped jected to vibrations in each test and no shotcrete
on shotcrete panels. Different loading rates and area was subjected to vibrations more than once.
panel configurations were tested. The result was The geometry of a test site is described in Figure 1.
Accelerometers
in rock Shotcrete areas
40-80 mm thick
Accelerometers
on rock surface
CA A
m m Age: appr 9 to 25 hrs.
5 3.5m 1.5+1.5 x o Axge: aoppr 1 xto 2 hors. x
7m 10 m
Long explosive
charge Shotcrete area
Appr. 40o
relative to
tunnel wall
A-A
Figure 1. Schematic view of a test site. Explosive charge in rock behind shotcrete areas (Ansell & Holmgren 2001).
3
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