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Schubert, Wulf

1 
 
 
Support design for tunnels with large overburden in 
weak rock 
 
Wulf Schubert 
Institute of Rock Mechanics and Tunnelling, Graz University of Technology, 
NAWI Graz, Austria 
schubert@tugraz.at 
 
 
 
Often damages of the lining and failure of bolts is a result of tunnelling in weak rock under 
high stresses. Large displacements can lead to violation of the clearance profile, requiring 
costly, dangerous, and time-consuming repairs.  
The main problem is that conventional supports have a rather limited strain tolerance. 
Shotcrete for example can tolerate maximum 0.6% to 0.8% strain without failure. Any 
imposed strains beyond this level will lead to destruction of the lining and consequently a 
more or less complete loss of support resistance, causing additional displacements and 
disintegration of the rock mass.  
Over the last two decades, ductile elements have been developed and successfully used on 
a considerable number of tunnels. The aim of those elements is optimally utilizing the 
capacity of the lining, while preventing damage of the lining by limiting the resistance. 
Although this sounds simple, the task of designing such a ductile lining system is not at all 
trivial. Many factors need to be considered, like development of the displacements in 
relation to face advance and time. The ground structure and the relative orientation 
between the tunnel axis and dominating geological features, like foliation or bedding 
strongly influence the longitudinal displacement profile. The development of the 
displacements over time also depends on the advance rate, influencing the degree of 
utilization of the shotcrete, which changes its properties over time.  
Currently used ductile element systems are presented and their characteristics as well as 
pros and cons discussed. More or less sophisticated tools for a preliminary design of ductile 
linings exist. Examples of application are presented. 
Another issue is the performance of grouted rock bolts under large strains. Installation of 
bolts at the time of the largest strain rates in the rock mass close to the face results in 
considerable shear strains in the grout, while it is setting. This may lead to a loss of bond 
between bolt and ground, making the bolts more or less ineffective. Special rib designs of 
the bolts can reduce this effect.  
 
INTRODUCTION 
 
It is well known that tunnelling in fault zones at a high primary stress level can lead to damages in the 
support (Figure 1), associated with at least partial loss of its resistance. This again leads to further 
disintegration of the ground and additional loss in its quality. Additional displacements or even a 
collapse may be the consequences. In addition costly, time consuming and hazardous repairs are 
required. Traditional methods to prevent damage to shotcrete linings are simply leaving gaps in the 
lining (Pöchhacker et al., Schubert, 1993, 1996). This pragmatic approach reduced the requirement for 
repairs, but resulted in a poor utilization of the shotcrete lining, thus leading to relatively large 
displacements (Figure 2). In addition, the system´s stability with such an approach heavily relies on the 
installed bolts. A tunnel collapse showed that the bond of grouted bolts can be significantly reduced by 
imposed large strains during the grout setting period (Schubert, 1995, Blümel, 1996). This accident 
triggered the development of improved grouted bolts and ductile lining systems. A first series of ductile 
elements, integrated into the shotcrete lining were used in 1994 at the Galgenbergtunnel in Austria 
(Schubert et al, 1996). Those relatively simple elements showed a strong variation in their resistance 
during the folding process. Improvements of the system followed, providing a more steady reaction of 
the elements (Moritz, 1999), but at the price of relatively high production effort and costs. Successful 
2 
 
applications in various projects showed that displacements could be much better controlled and 
significantly reduced compared to the system with the open slots. Increasing the efficiency of the 
elements while reducing the costs was the motivation for further developments at our institute 
(Sitzwohl, 2011, Verient, 2014, Brunnegger, 2017).  
 
 
 
Figure 1. Typical damage of shotcrete lining due to large displacements. Photo: Schubert 
 
 
 
 
Figure 2. Open gaps in the shotcrete lining at the Inntaltunnel, Austria. Photo: Schubert 
 
Once it is established that in a project larger displacements have to be expected, which cannot be 
controlled by conventional supports, type, quantity and properties of the support elements have to be 
determined. This requires the review of a number of issues, like displacement development in relation 
to time and face advance, or time dependent properties of shotcrete. 
 
 
 
 
3 
 
DISPLACEMENT DEVELOPMENT AND UTILIZATION OF LINING 
 
A number of parameters influence the development of the displacements in relation to time and face 
advance. Among other influences, the degree of utilization of the ground, the rock mass structure, 
creeping of the rock mass, as well as the advance rate play a dominant role. 
The development of the displacements can be easily described by equation 1 (Sulem et al, 1987). 
Evaluating a large number of monitoring results allowed establishing the reliability of above equation. 
 
 
 
  [1 
 
 
An example shall demonstrate the influence of the advance rate on the development of the 
displacements over time. For the sake of simplicity, time dependent rock mass behaviour is neglected 
(m is set to zero).  
The presented example uses following parameters: X =20, xC = 55 mm. The development of the 
displacements versus time is calculated for advance rates of 2 m per day, 4 m per day, and 6 m per day. 
Figure 3 shows the significant influence of the advance rate on the development of the displacements 
over time. While for the smallest advance rate of 2 m/d, the displacements after 24 h are in the range of 
10 mm, for the advance rate of 6 m/d they amount to approximately 22 mm. 
 
Figure 3. Displacement development versus time for advance rates of 2 m/d, 4 m/d, and 
6  m/d 
 
Shotcrete exhibits a pronounced time dependent behaviour, with effects of creeping, shrinking, and 
temperature. A relatively realistic description of the time dependent properties is possible with the flow-
rate method (Schubert, 1988). This allows evaluating the stresses in the lining at any time, and thus 
comparing it to the actual strength. This can be expressed as degree of lining utilization.  
Evaluating the degree of lining utilization for the different displacement developments described above, 
for a 10 m diameter tunnel with a 20 cm shotcrete lining with an early strength class J2, and a strength 
of 30 MPa after 28 days. 
Figure 4 shows the result of the evaluation. While for the lowest advance rate with 2 m/d the lining´s 
utilization is a maximum of approximately 70%, for the advance rate of 4 m/d the safety margin against 
lining failure is minimal, and with the highest advance rate the lining would be damaged. 
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Figure 4. Degree of lining utilization for different advance rates 
 
The example clearly demonstrates that the advance rate with otherwise unchanged conditions with 
respect to ground and lining quality has an important influence on the probability of lining damage.  
 
 
DEVELOPMENT OF YIELDING ELEMENTS 
 
Basic Considerations 
 
Once the probability of lining failure is identified, appropriate strategies need to be developed to allow 
for safe and “comfortable” tunnelling. As mentioned, the traditional method applied in the Alps by 
leaving slots without shotcrete in the lining results in a relatively low utilization of the installed lining, 
and also – due to the low resistance –to relatively large displacements, also affecting the bond of the 
bolts, and contributing to additional deterioration of the ground. 
The ground reaction curve clearly demonstrates the effect of a controlled development of lining 
resistance. The weaker the ground the higher is the effect.  
 
Figure 5 shows a comparison of displacements evaluated for a lining with open slots and rock bolting 
and a lining with integrated yielding elements. The result is quite impressive and corresponds well with 
experience on various sites, where with the ductile lining system the displacements could be reduced 
by roughly 50% compared to previously constructed tunnels in the same conditions with open gaps. 
 
 
 
Figure 5. Effect of integrated yielding elements on the displacements (Radoncic, 2011) 
5 
 
 
Requirements 
 
As shown in the previous chapter, there are quite a number of factors influencing the interaction 
between ground and support. Practically it is not feasible to provide a wide range of yielding elements 
with different characteristics to account for all conditions. This implies that a limited number of types 
of elements are provided, with specifications regarding the range of feasible application. Adjustment to 
displacement development and magnitude is possible by using different element types or number of 
elements in the lining. 
First, the expected range of displacements, as well as the longitudinal development have to be assessed. 
Then, using previous studies with respect to required resistance at acceptable load levels (Sitzwohl, 
2011) the layout of the elements can be fixed. 
 
 
Figure 6. Optimal resistance of the elements in relation to face advance rate for certain 
tunnel deformation conditions (Sitzwohl,  2011) 
 
Example  
 
Figure 7 shows the history of the lining utilization for cases, assuming a final displacement in the range 
of 95 to 115 mm, an advance rate of 4 m/d, and a varying longitudinal displacement development. The 
criterion set for this example was a maximum lining utilization of 60%. 4 rows of yielding elements Type 
LSC II in a 10 m diameter, full face excavated tunnel are chosen.  
6 
 
 
 
Figure 8. Displacement – time diagrams satisfying the requirement of maximum 60% 
utilization of the lining capacity and critical limit for the case with X=12 
 
In case the displacements expected (or measured) approach the critical limit, a change either of the 
element type or the number of elements in the cross section is required. 
 
Figure 9 shows a reasonable distribution of yielding elements in the lining for conditions with 
approximately isotropic displacement distribution (left), and the application at the second tube of the 
Tauerntunnel, Austria, where concentrated strains were expected in the shoulders (right). It should be 
mentioned that for a maximum utilization of the lining capacity, a relatively short ring closure distance 
is advisable. 
Figure 7. Range of scenarios providing a lining utilization of 
maximum 60% 
7 
 
  
 
Figure 9. Layout of yielding elements in the cross section (left), and application in the top 
heading of the Tauerntunnel. Austria (right, Photo: Vergeiner) 
 
 
Types of Elements on the Market  
 
Although yielding elements are not a mass product, a couple of models are on the market (Figure 10). 
Some of those are based on a cementitious porous material; others are made from pure steel in various 
layouts. The latest development of our institute is a combination of steel and porous material, taking 
advantage of the benefits of both systems. The shortcomings of the porous cement based elements are a 
relatively high initial stiffness until failure of the matrix, and the potential for disintegration during the 
deformation process. In addition, the development of the resistance with increasing strain is far from 
the desired path. 
 
 
Figure 10. Different types of yielding elements; top left: type LSC (Dywidag Systems), top 
right: system GRA7_A (SZ Streckenausbau); bottom left: system HiDCon 
(Solexperts); bottom right: system Wabe (Eisenhütte Bochum) 
 
Recent modification of the LSC system included the combination of steel tubes with porous fillers 
(Brunnegger, 2017). Using special steel and a combination of fillers with different characteristics allowed 
achieving a load-displacement characteristic, being close to the optimum. 
8 
 
 
 
Figure 11. Latest model of the yielding elements type LSC+ after approximately 65% 
shortening, and force-strain diagram (Schubert et al, 2016) 
 
With further modifications of the filler composition, the characteristic will improve further. 
Adjustment of the number of elements integrated into the lining allows using the same element type for 
a wide range of displacement magnitudes. However, the gaps should be chosen in a sufficient number 
to avoid distortion of the bolts and the subsequent likelihood of failure of the bolt head. At the location 
of the elements a concentrated deformation occurs, resulting in a shearing between lining and ground 
(Figure 12).  
 
 
Figure 12. Concentrated deformation in the area of the elements leading to distortion of 
bolts and shearing between ground and lining (Radoncic, 2011) 
 
Typical indications of this phenomenon are deformed head plates, in particular close to the gaps. Using 
a deformable sleeve close to the bolt head can reduce the effect, but in general, a change to a higher 
number of slots is advisable. 
 
9 
 
ROCK BOLTS 
 
Using grouted bolts is standard in weak rock conditions. The high deformation rates close to the face 
Installation of the bolt close to the face can negatively influence the setting process of the grout. This can 
result in a shearing of the “fresh” grout, and thus a loss in bond between bolt and ground.  
Investigations revealed that the rib geometry has a significant impact on the development of the bond 
(Blümel, 1996).  It showed that conventional rib designs, as applied in reinforced concrete have a rather 
close rib distance. This increases the stiffness of the reinforcement if the grout can set undisturbed. In 
tunnels, the large strains imposed on the grout, while it is setting have a detrimental effect on the 
development of the bond. Laboratory tests on grouted bolts, subjected to a constant strain rate during 
setting of the grout showed that the pull out resistance generally increases with larger rib distances 
(Figure 13).  Grout properties and strain rate do have an influence, but the general trend is the same. 
Unfortunately, conventional pull out tests of grouted bolts do not provide a conclusive result. The 
relative displacement of the bolt to the ground close to the lining due to the fixing to the lining is small, 
and in this area, the grout can set more or less undisturbed. This results in a good bond close to the bolt 
head, yielding satisfying test results. However, no information about the bond further away from the 
tunnel perimeter, where the shear strain between continuously increases are obtained with such a test. 
This raises also the question whether increasing the bolt length in difficult ground conditions with high 
deformation rates provides any improvement. Probably a better investment is using a higher number 
of bolts with moderate length.  
 
 
 
Figure 13. Pull out force in relation to the rib distance of grouted bolts (Blümel, 1996); 
cs=rib distance 
 
 
CONCLUSION 
 
The layout of supports for tunnels with large stress induced displacements has to be done with much 
care. The inherent probability of lining failure and consequently its loss in bearing capacity has to be 
accounted for by using carefully designed special support elements. Good experience was made with 
ductile elements, being integrated into a shotcrete lining in combination with grouted bolts with a 
special rib design. The parameters for the detailed layout of the supports are expected displacement 
magnitude, development of displacements over time – which again to a considerable extent depend on 
the advance rate – and shotcrete properties. During construction, an appropriate monitoring helps in 
timely adjustment of excavation and support to the actual ground conditions and system behaviour.  
REFERENCES 
10 
 
Blümel, M. (1996). Untersuchungen zum Tragverhalten vollvermörtelter Felsbolzen im druckhaften 
Gebirge. PhD Thesis. Institute for Rock Mechanics and Tunnelling, Graz University of Technology. 
Brunnegger, S. (2017). Optimierung der Lining Stress Controller durch zementgebundene poröse 
Füllung. Master Thesis, Graz University of Technology (in preparation) 
Moritz, A.B. (1999).  . In: Riedmüller, Schubert & Semprich (eds.), Publication Series Gruppe Geotechnik 
Graz, Vol 5, Graz University of Technology, Austria. 
Pöchhacker, H. (1974). Moderner Tunnelvortrieb in sehr stark druckhaftem Gebirge. Porr Nachrichten 
57/58. 
Radončić, N., (2011). Tunnel design and prediction of system behaviour in weak ground. In: Dietzel, Kieffer, 
Schubert, Schweiger, Semprich (eds.) Publication Series Gruppe Geotechnik Graz, Vol 43 
Schubert, P. (1988). Beitrag zum rheologischen Verhalten vom Spritzbeton. Felsbau 6 (3), 150–153. 
Schubert, W. & Riedmüller, G. (1995). Geotechnische Nachlese eines Verbruches – Erkenntnisse und 
Impulse. Proc. 10th Christian Veder Kolloqium, Semprich et al. (eds.). Graz. 
Schubert, W. & Riedmüller, G. (1995). Geotechnische Nachlese eines Verbruches – Erkenntnisse und 
Impulse. Proc. 10th Christian Veder Kolloqium, Semprich et al. (eds.). Graz. 
Schubert, W. (1993). Erfahrungen bei der Durchörterung einer Großstörung im Inntaltunnel. Felsbau 11 
(6), pp. 287-290, Essen: Verlag Glückauf. 
Schubert, W. (1993). Erfahrungen bei der Durchörterung einer Großstörung im Inntaltunnel. Felsbau 11 
(6). 287-290 
Schubert, W. (1996). Dealing with squeezing conditions in alpine tunnels. Rock Mechanics and Rock 
Engineering 29 (3). 
Schubert, W. 1996. Dealing with squeezing conditions in alpine tunnels. Rock Mechanics and Rock 
Engineering 29 (3), pp. 145-153, Springer: Wien. 
Schubert, W., Golser, J. & Schwab, P. (1996). Weiterentwicklung des Ausbaues für stark druckhaftes 
Gebirge. Felsbau 14 (1), pp. 36-42, Verlag Glückauf: Essen. 
Sitzwohl, M. (2011). Optimierung der Lining Stress Controller durch zementgebundene poröse Füllung. 
Master Thesis, Graz University of Technology  
Sitzwohl, M. 2011. Optimierung der Lining Stress Controller durch zementgebundene poröse Füllung. 
Master Thesis, Graz University of Technology  
Sulem, J., Panet, M. & Guenot, A. (1987). An analytical solution for time-dependent displacements in a 
circular tunnel, Int. J. Rock Mech. Min. Sci. & Geomech. Abstr. Vol 24, No. 3, 155-164. 
Solexperts. 2016. hiDCon – High deformable Concrete.  
http://www.solexperts.com/index.php/de/component/docman/doc_download/815-
de19geohidconbetonv4.html [accessed 23.Oct.0.2016]: 
SZ Schacht- und Streckenausbau GmbH. 2014. Nachgiebigkeitselement, Gebrauchsmusterschrift, S. 3, 
Deutsches Patent- und Markenamt, Deutschland 
Verient, M. (2014). Investigations on telescopic yielding elements with porous filling. Master Thesis, 
Graz University of Technology 
11 
 
 
Authors CV  
 
Prof. Wulf Schubert 
Full Professor 
Institute of Rock Mechanics and Tunnelling 
Graz University of Technology 
 
Mr. Wulf Schubert is full professor and head of the Institute of Rock 
Mechanics and Tunnelling at the Graz University of Technology since 
1992 and founding partner of 3G Gruppe Geotechnik Graz Consulting 
Engineers. He is a tunnelling expert with international experience. 
Besides his lectures in the field of rock mechanics and tunnelling in 
bachelor and master courses, he supervised more than 70 master theses 
and 20 dissertations. Additionally he is programme director and lecturer 
of a university programme in NATM Engineering. 
 


Support design for tunnels with large overburden in weak rock

Brunnegger, Stefan

Proceedings of the World Tunnel Congress 2017 – Surface challenges – Underground solutions. Bergen, Norway. 
1 
1 INTRODUCTION 
Tunnelling in poor or faulted rock is associated 
with a number of problems. One of the 
problems, addressed in this paper are the 
relatively large displacements, incompatible 
with conventional shotcrete supports. Besides 
general overstressing of the lining in quasi-
homogeneous ground, also shearing along 
foliation or slickensides and faults can be 
frequently observed (Figure 1). 
 
 
Such damages are a safety hazard and require 
extensive repair works.  
The traditional method to prevent lining failure 
is simply leaving open slots in the lining, which 
are filled once the displacements have come to a 
halt (Figure 2). This is a pragmatic approach, 
but results in a poor utilization of the lining, and 
thus to large strains in the rock mass, which can 
lead to considerable deterioration of the rock 
mass quality. 
 
 
Papers should be typed in Times New Roman 
under MS Word format (.doc or .docx, no .pdf)  
New ductile tunnel lining system 
W. Schubert 
Graz University of Technology, NAWI Graz, Austria. 
S. Brunnegger 
Graz University of Technology, Graz, Austria. 
 
 
 
 
ABSTRACT: Tunnelling with high overburden in poor or faulted rock masses frequently leads to 
large displacements, damaging conventional supports. Ductile support systems allow accommodating 
the large strains imposed on the lining without damage. With an appropriate design and layout of the 
support, it can develop a controlled resistance, thus reducing displacements. Development of yielding 
elements has started many years ago, but only during the last 20 years, practical application has 
become common practice. Various requirements have to be considered in the design of ductile 
elements, which are integrated in the conventional supports. Among other factors, the time 
dependent development of the properties of shotcrete, as well as the development of the 
displacements with time – which again depends on the advance rate - play an important role. Graz 
University of Technology during the last two decades has worked on the development of ductile 
elements for shotcrete linings. The paper gives an overview of the development and the current state. 
Figure 1. Typical shearing of shotcrete lining along 
slickenside (Rohtang tunnel, India) 
Figure 2. Support with open slots in the lining 
(Innatltunnel, Austria) 
Proceedings of the World Tunnel Congress 2017 – Surface challenges – Underground solutions. Bergen, Norway. 
2 
2 BASIC CONSIDERATIONS 
Shotcrete has a pronounced time dependent 
behavior. An increase in stiffness and strength is 
accompanied by creeping and shrinking, and 
influenced by temperature, caused by the 
hydration process. By experience the critical 
strain of a shotcrete lining has been identified to 
be in the range of 0.6% to 0.8% (Schubert, 
1996). 
On the other hand, development of 
displacements primarily depends on the face 
advance and only to a minor extent on the time 
dependent effects. This implies that the imposed 
strain over time predominantly depends on the 
advance rate.  
This effect has been studied by Sitzwohl 
(2011) and Radoncic (2011). Considering a 
maximum utilization of the shotcrete capacity of 
80%, the desired capacity of the yielding 
elements can be calculated in relation to the 
advance rate of the face. Figure 3 shows an 
example of such an evaluation, considering the 
time dependent behavior of shotcrete. 
 
Figure 3. Optimum load lines for yielding elements in 
relation to the advance rate (Sitzwohl, 2011) 
As discussed above, linings with open slots 
do not develop much resistance against ground 
deformation. Only friction between the lining 
and the ground and the shear resistance of the 
bolts provides a limited amount of support 
resistance. With integrated yielding elements, 
the lining´s capacity is much better utilized, thus 
considerably reducing ground and system 
displacements. This effect can be clearly 
demonstrated with the ground reaction curve 
(Figure ). 
 
Figure 4. Effect of integrated yielding elements on the 
displacement of a tunnel (Radoncic, 2011) 
Better utilizing the lining capacity not only 
reduces the displacements and thus the imposed 
strain of lining and bolts, but also helps in 
preserving the ground quality. In addition, the 
lining resistance increases the safety, as the 
probability of collapses reduces. 
3 DEVELOPMENT OF DUCTILE 
ELEMENTS 
3.1 Historical development 
To better utilize the lining capacity and at the 
same time reduce displacements, yielding 
elements, which are integrated in the lining, 
have been developed.  
A first series of such elements has been 
developed by our institute in the 1990ies. Those 
elements consisted of a group of axially 
arranged steel tubes with a head and foot plate 
(Figure ). Those elements worked quite well, 
but had the disadvantage, that the load line was 
oscillating in a wide range due to the different 
Figure 5. Load-displacement characteristic of original yielding 
elements (Schubert & Riedmüller, 1995, Moritz, 1999) 
Proceedings of the World Tunnel Congress 2017 – Surface challenges – Underground solutions. Bergen, Norway. 
3 
stages of formation of the single folds (Figure ). 
 
Figure 6. First series of yielding elements integrated into 
shotcrete lining at the Galgenbergtunnel, Austria 
By adding additional restraining tubes, 
Moritz (1999) has improved the characteristics 
of the system (Figure ). This yielded a much 
smoother load displacement characteristic 
(Figure ), as well as a higher energy absorption.  
Those elements were used at many tunnels in 
various countries under the name LSC (Lining 
Stress Controllers).  
Among other projects, the system was also used 
at the second tube of the Tauerntunnel in 
Austria (Figure ), reducing the displacements by 
more than 50% compared to the same location 
in the first tube. 
The production of this type of element was 
relatively complex and required a certain 
precision in the manufacturing process, as well 
as during installation. Asymmetrical folding due 
to imperfections in the production or installation 
to a certain extent influences the performance of 
the elements.  
 
Figure 8 Improved yielding element (Moritz, 1999) 
 
Figure 9. Use of yielding elements in the Tauerntunnel, 
Austria (Photo: Vergeiner) 
Realizing the advantages of such yielding 
supports, different producers introduced their 
products to the market (Figure 10). Some of 
those are based on a cementitious porous 
material, others are using steel only. The 
disadvantage of the porous material is the fact 
that in general the initial stiffness is too high, 
requiring additional soft layers to achieve a 
satisfying characteristic. The systems based on 
steel elements have the tendency to be rather 
heavy, making their installation a challenge for 
the crew.  
Figure 7. Load-shortening diagram of the improved 
elements (Moritz, 1999) 
Proceedings of the World Tunnel Congress 2017 – Surface challenges – Underground solutions. Bergen, Norway. 
4 
 
Figure 10. Various different yielding elements; top: 
System HiDCon (solexperts), center: System Wabe 
(Eisenhütte Bochum); bottom: System GRA7-A 
(SZ Streckenausbau) 
3.2 Latest development 
Bearing in mind the advantages and 
disadvantages of the various systems, our 
institute recently combined the advantages of 
the steel systems with the benefits of the porous 
filler. The result was a system of steel tubes 
with a porous cement bonded filler. Special 
steel is required to allow for large strains, as 
well as a kind of sandwich type composition of 
the filler in order to come close to the desired 
behavior.  
A considerable number of tests, varying the 
filler composition, as well as the steel type was 
required to achieve the desired results (Verient, 
2014, Brunnegger, 2017). Figures 11 and 12 
show the current result of the development. 
Optimizations of the systems in terms of 
material selection and production will follow.  
 
 
 
Figure 12. Test result of element type LSC-N, upscaled 
for one linear meter of tunnel (Brunnegger, 2017) 
CONCLUSION 
The use of ductile elements in combination with 
conventional shotcrete and bolt supports has a 
number of advantages, such as considerable 
reduction of displacements, while maintaining 
the integrity of the lining. However, the 
parameters influencing the layout and 
composition of ductile elements is manifold. 
Besides the ground quality and deformation 
characteristic, shotcrete properties, as well as 
advance rate of the heading plays an important 
role. As not all those parameters are completely 
known prior to construction, a certain potential 
for modification of the system performance on 
site should be available. None of the systems 
currently on the market provides this option in a 
satisfactory way. There is still room for 
improvement, and we will follow the topic up.  
Figure 11. Combination of steel cylinder and porous 
filler, Type LSC-N after shortening of approximately 
65% (Brunnegger, 2017) 
Proceedings of the World Tunnel Congress 2017 – Surface challenges – Underground solutions. Bergen, Norway. 
5 
REFERENCES 
Brunnegger, S., 2017. Optimierung der Lining Stress 
Controller durch zementgebundene poröse Füllung. 
Master Thesis, Graz University of Technology (in 
preparation) 
Moritz, A. B., (1999). Ductile Support System for 
Tunnels in Squeezing Rock. In: Riedmüller, Schubert 
& Semprich (eds.) Publication series Gruppe 
Geotechnik Graz, Vol. 5 
Radončić, N., Schubert, W. & Moritz, B. 2009. Ductile 
support design. Geomechanics and Tunnelling 2 (5), 
S. 561-577, Ernst & Sohn: Berlin. 
Radončić, R., 2011. Tunnel design and prediction of 
system behaviour in weak ground.. In: Dietzel, 
Kieffer, Schubert, Schweiger, Semprich (eds.) 
Publication series Gruppe Geotechnik Graz, Vol. 43 
Schubert, W., & Riedmüller, G. (1995). Geotechnische 
Nachlese eines Verbruches - Erkenntnisse und 
Impulse. In: Semprich, S. (ed.), Innovationen in der 
Geotechnik; Proc. 10. Christian-Veder-Kolloquium, 
Graz, 20-21 April 1995, pp. 59-68. Institut fuer 
Bodenmechanik und Grundbau, Graz University of 
Technology: Graz. 
Sitzwohl, M. 2011. Optimierung der Lining Stress 
Controller durch zementgebundene poröse Füllung. 
Master Thesis, Graz University of Technology 
Solexperts. 2016. hiDCon – High deformable Concrete.: 
http://www.solexperts.com/index.php/de/component/d
ocman/doc_download/815-
de19geohidconbetonv4.html 
SZ Schacht- und Streckenausbau GmbH. 2014. 
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