Wulf Schubert

• Head of Department at Graz University of Technology

Brittle fault zones in Alpine environments usually are strongly heterogeneous. This implies significantly varying stresses and displacements in the ground and the underground structure. Major overbreaks and collapses are common events under such conditions. Analysing a couple of these events in Alpine tunnels it was found that there is a higher pro...

The failure hazard rock burst is very dangerous as it can occur very suddenly and violent-ly. Due to the fact, that tunnel and mining projects are in deeper areas than ever, the im-portance of investigating this hazard is more relevant than ever. The Graz University of Technology and the University of Salzburg are investigating rock burst with diff...

This paper introduces the successful implementation of a fibre-optic sensing system for direct and distributed strain measurement within the shotcrete lining of a conventional tunnel drive. The shotcrete lining of the top-heading and the invert are equipped with two layers (rock side and cavity side) of fibre-optic sensing cables installed in circu...

A 1 km long excavated section of the Semmering Base Tunnel has been analysed. With a few exceptions, two distinct and continuous features of the system behaviour can be observed: (1) the displacements of the sidewalls are larger than of the crown and of the shoulder points; (2) the displacements of the right sidewall are larger than those of the le...

In modern tunneling, the assessment of the structural integrity is usually based on displacement measurements of the tunnel lining using total stations or on readings of electrical strain gages embedded inside the liner. However, these technologies only deliver information on particular points rather than a complete picture of the linings’ deformat...

Geophysical Research AbstractsVol. 21, EGU2019-17048, 2019EGU General Assembly 2019© Author(s) 2019.A method and work flow for quantifying Rock Burst in 4DRobert Marschallinger (1), Peter Hofmann (1), Fritz Zobl (1), Richard Ketcham (2), Dave Edey (2), LukasGottsbacher (3), Angelika Klammer (3), and Wulf Schubert (3)(1) Department of Geoinformatics...

Knowledge about the joint network is important in rock engineering. It controls the stability and strength of blocky rock masses. Thus, the joint network is mapped in more or less detail, regarding the specifications. To do so, different methods have evolved over the years. One of these methods is digital mapping, based on the visual and spatial ap...

Rock mass characterization is very important in rock engineering. The characterization encompasses the description of the apparent joint network as well as the spatial distribution of ground types or lithologies. Currently, the rock mass is documented and mapped either on-sight or with digital mapping-software like ShapeMetriX3D on the desktop. In...

During a shield TBM excavation in hard rock, the immediate backfill of the crown immediately behind the shield is technically difficult to realize. With the advance of the cutter head a relocation process of pea gravel within the annular gap is triggered, leading to an insufficient bedding distribution of the first segments behind the shield tail a...

Yielding elements in combination with shotcrete linings are used in Austria since 1994, replacing the previous method of leaving open gaps. The first system, used at the Galgenbergtunnel, consisted of groups of axially loaded steel pipes with manufactured local weakness. The resistance of those elements showed a pronounced oscillation during shorte...

In modern tunnelling, deformation monitoring is an important component to ensure a safe construction and a long lifetime of the tunnel. It is state of the art to measure displacements at the surface of the tunnel lining using total stations or terrestrial laser scanners and internal deformations with electric strain gauges. However, these measureme...

Like every civil engineered structure tunnels are subject to an ageing process. The reasons for the degrading of the condition are manifold: not fully completed stress redistribution, deterioration in the rock mass quality through long‐term exposure (creeping), weathering or dynamic loads and stresses, to name but a few. All this processes lead to...

en The Institute of Rock Mechanics and Tunnelling at the Graz University of Technology was founded in 1992. From the beginning, the primary focus of research and development was on Alpine tunnelling and slope stability issues, considering geological conditions and their impact on construction. The aim was to improve the current practice, as well as...

When using shield machines, the excavation support is established using prefabricated concrete segments. The structurally required cavity between the built ring and the rock mass is usually filled with pea gravel in hard rock conditions. The backfilled material ensures the necessary bedding and evenly distributes the rock loads. To evaluate the in‐...

For the design of rock engineering projects, rock mass parameters are usually determined by the use of classification systems (Q, GSI, RMR, etc.). A homogeneous rock mass with reduced parameters via empirical relationships is generated, and the influence of the anisotropy is lost during the process. The influence of discrete discontinuities on the...

The influence of discontinuities on the mechanical behavior of rock masses, demands a detailed knowledge about the geometrical properties of the existing discontinuity network. Traditional measurement techniques provide a rough knowledge about a discontinuity network but are also prone to bias. To increase the reliability of discontinuity models, r...

The relative orientation of foliation or closely spaced bedding has an important influence on the behavior of underground structures. Not only the potential failure mode is controlled by the relative orientation between underground opening and foliation strike, but also the longitudinal development of the displacements. Case histories and numerical...

With mechanized shield tunnelling the quality of the backfill is of significant importance for the stability of the lining. The used material affects the interaction between support and rock mass. Therefore, the choice of a proper backfilling material is of great importance for the system behaviour.

en 3GSM rolled out its first rock mass characterization system for conventional tunnelling in 2005. It consisted of a digital camera, as well as software components for 3D image generation and geologic mapping. It took several years before such a system became standard procedure on tunnelling sites. The same principles were applied later to mechani...

The ROCKBURST project researches the influence of micromechanical and micro-structural characteristics and their individual effect on rock failure. In this project, we use Ob-ject based image analysis (OBIA) for knowledge-based, automated mineral classification and rock texture analysis from petrographic micrographs. Our work flow closely mimicks a...

In den letzten Jahren wurden durch das Aufkommen von Fernerkund ungsmethoden große Fort-schritte in der ingenieurgeologischen Gebir gscharakterisierung erreicht. Ehemals subjektive und schwer reproduzierbare Daten, wie z.B. über das Trennflächengefüge in ei ner Ortsbrust werden heutzutage durch Ergebnisse aus digitalen Trennflächenkartierungen erse...

Special considerations are required for the support of tunnels in fault zones. On the one hand, standard support elements are not compatible with the imposed displacements. On the other hand, local shearing can cause damage to the lining already at rather small displacements magnitudes. Cracks in the lining frequently are observed, when the geometr...

The program for the final disposal of low and intermediate level radioactive waste was established by Paks Nuclear Power Plant, Hungary. Preparation of final disposal has been done as part of a national program since 1993. The Central Nuclear Financial Fund and the Public Limited Company for Radioactive Waste Management (Puram) have been establishe...

Interdisciplinary research on (micro)crack patterns in rock-burst prone materials

In this paper, the effect of rock bridge surface on the shear behavior of planar non-persistent joints under low and high normal loads has been investigated using particle flow code in 2 Dimensions. PFC2d was calibrated with respect to the data obtained from experimental laboratory tests to ensure the conformity of the simulated numerical models re...

The present study considers the tensile strength of concrete samples in direct, flexural, double punch and ring tests using both of the experimental tests and numerical simulation (particle flow code 2D). It determined that which one of indirect tensile strength is close to direct tensile strength. Initially calibration of PFC was undertaken with r...

It is often very difficult to perform a long-term monitoring programme to measure displacements of structures in remote areas like high rock buttes in alpine regions, where the direct installation of measurement devices and a constant reading is, due to low accessibility, not possible or too expensive. In most cases, tape extensometers or distance...

It is often very difficult to perform a long-term monitoring programme to measure displacements of structures in remote areas like high rock buttes in alpine regions, where the direct installation of measurement devices and a constant reading is, due to low accessibility, not possible or too expensive. In most cases, tape extensometers or distance...

Discontinuities dominantly influence the mechanical behavior of rock masses. Thus, it is of crucial importance in rock engineering to have a profound knowledge about the discontinuity network. Traditional measuring techniques provide only a rough knowledge about a discontinuity network and are prone to human bias. To increase the reliability of dis...

With mechanized shield tunnelling the quality of the backfill is of significant importance for the stability of the lining. The used material affects the interaction between support and rock mass. Therefore, the choice of a proper backfilling material is of great importance for the system behaviour. Scaled model tests have been carried out investig...

The PURAM (Public Limited Company for Radioactive Waste Management) is the owner and operator of the National Radioactive Waste Repository in Hungary. The facility ensuring the final deposition of the low and intermediate levele radioactive wastes and it is situated beside the Báta- apáti village, excavated in a granitic host rock. During the excav...

Tensile strength is one of the important mechanical properties of concrete. Indirect methods have been used up till now for its measurement. These methods though widely accepted, do not furnish the true tensile strength of concrete. In this paper, a compression to tensile load transformer device is developed to determine direct tensile strength of...

In this paper, a compression to tensile load converter device was developed to determine the anisotropic tensile strength of concrete. The samples were made from a mixture of water, fine sand and cement, respectively. Concrete samples with a hole at its center was prepared and subjected to tensile loading using the compression to tensile load conve...

No abstract is available for this article.

Currently there is no uniform and consistent documentation of unexpected standstills available, which can be applied during the excavation of tunnels with tunnel boring machines (TBM). Such a documentation and evaluation would be helpful for the estimation of risks, costs and the advance rate for future tunnels excavated with a TBM. An approach for...

Tunnelling in weak ground and under high overburden always proves to be challenging during the design and construction phase. Currently, tunnels are constructed with great lengths, which increases the probability of crossing tectonic fault zones under high overburden. These geological conditions are commonly associated with high loads and massive d...

Due to uncertainties in the ground model and the spread of geotechnical properties, prediction of the exact system behaviour of underground structures is difficult in many cases. In order to manage this problem, the so-called observational approach is often applied. Monitoring plays an important role to verify or falsify design assumptions, to adju...

No abstract is available for this article.

The in situ block size is a key parameter in the geomechanical characterization of rock masses. It describes the fracturing of the rock mass and thus is a measure for the degradation of the rock mass strength. Several classification systems use the in situ block size. For instance, the Geological Strength Index (GSI) requires the “blockiness” and j...

The term " squeezing " is frequently used, although it is ill defined. Definitions like " large and long lasting displacements " raise the questions about the threshold values for the magnitude and duration of displacements. Large displacements during tunnelling frequently are observed in fault zones with high overburden. Whether this causes proble...

The better the information on the rock mass and its structures, the better is the basis for any rock mechanical decision that is required during the excavation process. While in conventional tunnelling free view to the tunnel face is available, there are just limited possibilities available during mechanised tunnelling using a TBM. An approach, alr...

The effect of joint overlap on the full failure behavior of a rock bridge in the shear-box test was numerically investigated by means of the particle flow code in two dimensions (PFC2D). Initially, the PFC2D was calibrated by use of data obtained from experimental laboratory tests to ensure the conformity of the simulated numerical model’s response...

The inherent uncertainties in the ground model and influencing factors, in most cases, do not allow a reliable direct design of a tunnel. Empirical tunnel design methods do not allow proofing stability or serviceability, thus are not acceptable according to common understanding. To allow for construction of safe and economical tunnels, the uncertai...

Der Begriff NÖT wurde von Rabcewicz geschaffen, der ihn erstmalig beim Geomechanik Kolloquium 1962 verwendete. In seinem damaligen Beitrag fasst er die während der letzten Dekaden entwickelten Tunnelbaumethoden und die Vorstellungen über die Mechanik der Vorgänge im Gebirge zusammen. Aufbauend auf vorliegenden Erfahrungen und Erkenntnissen haben üb...

The term NATM was introduced by Rabcewicz during a lecture at the Geomechanics Colloquium in 1962. In this lecture, he summarizes the development of tunnelling methods and insight into mechanical processes in the ground over the last decades, and points out the positive experience made with a combination of shotcrete and rock bolts instead of the t...

Particle flow code 2D (PFC2D) was adopted to simulate the shear behavior of rocklike material samples containing planar non-persistent joints. Direct shear loading was conducted to investigate the effect of joint separation on the failure behavior of rock bridges. Initially calibration of PFC was undertaken with respect to the data obtained from ex...

Accidents, cost- and time overruns at tunnel projects are still rather common. It appears that design and construction procedures still do not comply with the requirements of an up to date engineering approach. Too often dominant behaviors during the design process are ignored or the models simplified in a way that critical mechanisms cannot be det...

When constructing long base tunnels passing various geological formations and tectonic faults, advance through weak ground under high overburden frequently occurs. Loads unsustainable by a stiff support concept, support damage and very costly re-profiling works are a frequent consequence. Various approaches for a ductile support system appropriate...

The project 'Large-scale deep geothermal power plants' follows a radically new approach to the exploitation of geothermal power. It relies on an underground power plant for gaining electricity from district and process heat. The concept foresees a complex mining infrastructure to construct closed systems allowing for controlled and continuous energ...

In many countries observations of the system behaviour are executed during tunnel construction. However, the enormous potential of modern monitoring and evaluation methods is frequently not utilised. This paper presents different and nowadays common evaluation methods and their benefit is highlighted. Case studies are used for illustration. Beobach...

The design of a ductile lining has to incorporate a number of influences. Both the influences of the ground conditions and the construction have to be considered in order to develop a safe and economical solution. Special focus has to be set on a plausible prediction of the time‐ and excavation‐dependent displacement development and its interaction...

A whole range of problems are generally associated with the construction of tunnels in weak ground and under high overburden. Among those are large displacements, wide variation of stresses and strains, and sudden water ingress, to name just a few. A wide variety of behaviours can be experienced, depending on the ground conditions and the influenci...

Pipe umbrella systems have effectively been used as an additional support system in the working area in weak ground conditions during the last decades. Thus, a considerable number of applications accounts in urban tunnelling with shallow overburden. However, this support system is also successfully used when a tunnel alignment crosses fault zones,...

The “Deep geothermal power station” project represents a new process for the exploitation of geothermal energy. District heating and heating for industrial purposes as well as electricity can be produced in a geothermal power station. The heat extraction will be controlled and continuous in a closed circulation system using drillings from a mined s...

Pipe umbrella support systems are used in weak ground conditions. The main reason for using this system is the supporting effect in the working area, which leads to safe construction conditions. Due to the complex stress transfer processes around the heading there is still a lack of knowledge regarding this system. Based on high quality measurement...

The Austrian Society for Geomechanics has published a guideline for the geotechnical design for underground structures with conventional excavation in 2001, which was revised in 2008. The guideline clearly focuses on the observational approach due to the uncertainties in the ground model and ground parameters in the design stage. In this paper the...

Tunnelling in difficult ground conditions induces high loads in the installed support, up to the point where ductile support concepts have to be considered. The usually installed shotcrete lining is subjected to very high strains during its ongoing hydration process, hence resulting in a very complex rheological behaviour. Only the combination of t...

Tunnelling in weak ground under high overburden normally results in very high displacements and if a stiff support concept is applied, this requires a very high load‐bearing capacity. This has again and again proved to be both an uneconomical and an unsafe concept, leading to extremely high lining thickness and brittle failure behaviour. In order t...

Displacement monitoring has been common practice during tunnel excavation for many decades. The results are usually used to assess the stabilisation process and to adapt excavation and support to the actual conditions. Although monitoring is done routinely on practically all sites, no consistent collection of case histories has yet been established...

The uncertainties in the ground model and the subsequent design of tunnels call for an observational approach. To enable the safe and economical tunnelling of underground infrastructure projects with shallow overburden, a safety management plan has to be implemented. The successful application of the observational method is based on a comprehensive...

Weak ground conditions are common in urban areas. In such ground conditions certain potential for instabilities in the working area exists. Therefore, additional support elements supplement the standard support system to achieve stable conditions during construction. The most known additional pre-support system is the face bolt, ensuring face stabi...

Measurement of displacements in tunnels is primarily used for the assessment of the stabilization process and the verification of the system behaviour. In addition the displacement data can be used for the prediction of changing ground conditions ahead of the face. For this purpose, the evaluation of displacement vector orientation turned out to be...

The final design of the pumped-storage project Feldsee features a complex lining and pre-stress grouting concept, rendering the method presented by Seeber insufficient for an accurate determination of the system behaviour in all stages of construction and operation. A calculation procedure based on the matrix stiffness method has been implemented,...

A continuous observation during construction always has been an important element of geotechnical engineering for minimizing risks. The reasons are the uncertainties in the geological and geotechnical models, as well as the limited capability to sufficiently accurately describe the complex ground behaviour. In the early days design of geotechnical...

SYNOPSIS: Pipe Umbrella support systems are effectively used as pre-support systems in tunneling to increase stability in the working area and decrease deformations induced by the construction. Its main application area is in weak ground tunneling. Either a Pre-Drilling or a Cased-Drilling method can install this system. Due to their characteristic...

Although the round length has a major technical and economical impact in conventional tunnelling, no coherent procedure is available for its determination. In this study, the determination of the round length was investigated for tunnels in weak rock, where the behaviour is not governed by discontinuities. This study focuses on shallow or medium de...

Using the rock mass as a load bearing element for high pressure hydro-tunnels can lead to considerable reductions in the wall thickness of the steel pipe. For a safe and economical design it is imperative to correctly assess the mechanical properties of the rock mass. The Feldsee project of the Austrian hydro-power company KELAG included an extensi...

In weak rock or under high overburden, considerable displacements occur during excavation of tunnels and galleries. The strains developing in many cases exceed the deformability of standard linings, frequently leading to severe damages and the necessity of costly repairs. To allow for a safe and economical tunnel construction, strategies have to be...

For more than twenty years, absolute displacement monitoring has been standard practice for tunneling projects in Europe. By correlating the monitoring results to specific geological conditions, it is now possible to forecast ground conditions ahead and in the vicinity of the tunnel face. To improve this forecasting, 18 characteristic scenarios, wh...

Under «squeezing» conditions, a tunnel lining must have a certain structural capacity but also should allow a controlled development of deformations. The idea to use precast segments with external ribs was already presented. Laboratory tests showed the expected and intended characteristic of an initial stiff phase when the ribs get in touch with th...

Keyblock analysis plays an important role in the evaluation of the behaviour of jointed rock. Remote sensing technologies are nowadays frequently used to provide the basis for those analyses. Metric 3D images provide accurate and detailed data on the rock mass structure and topography. This contribution outlines the use of metric 3D images for keyb...

Absolute displacement monitoring has become common practice on many tunnel sites. Those data in combination with the information on geological and boundary conditions have a tremendous potential to enhance the insight into mechanical processes around the tunnel and the ground-support interaction. Different methods of data evaluation are used for sp...

This case study presents a high resolution 3D imaging and assessment system and its application during the construction of a planned nuclear waste repository in Hungary. During the drill and blast excavation of two inclined access tunnels of about 1.800 m each the system is applied on a regular basis (every round) in order to support the undergroun...

Pipe Roof Support systems have increasingly been used in weak ground tunneling although the design is often based solely on experience. The results of an intensive measurement campaign, including settlement measurements ahead of the face, were used to determine a geotechnical model for this pre-support system. The measured ground-support interactio...

Stress redistribution, ground loss and change of groundwater table in the course of tunnel excavation cause surface settlements. These surface movements may cause damage to structures above and beside the tunnel. Experience shows that the timely and spatial influence of underground excavations on the surface settlements varies in a wide range. The...

In the planning and design phases of underground structures, the information on geological setup, the rock mass structure and characteristics necessarily is incomplete and inaccurate. To allow for a safe and economical construction, a continuous updating of the ground model and an adjustment of the construction methods to the actual site conditions...