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Underground excavation mapping and rock mass characterization are critical for ensuring the safety, proper design, and maintenance of underground infrastructure. Traditional mapping methods typically involve manual inspections and measurements that require contact with the tunnel surface, which can be time-consuming, expensive, and pose safety risks to personnel. In recent years, photogrammetry has emerged as an alternative method for generating high-resolution digital 3D models of tunnels, enabling rapid and remote rock mass measurements. In this paper, we present a method for tunnel and stope scanning using photogrammetry and remote rock mass mapping from 3D models. Two case studies are presented to demonstrate the effectiveness of the proposed method. In the first case, a multi-camera rig consisting of action cameras is used for video-based photogrammetric reconstruction of underground tunnel excavation. The rock mass data is then extracted from the model and visualized. In the second case, a drone workflow is used to map out rock mass features in stopes. Images taken with the drone are processed to create a 3D point cloud of the stope, which is then used to extract discontinuities from the rock mass surfaces. The orientation and spacing of these discontinuities are measured and visualized on top of the photorealistic 3D mesh of the stope for inspection. The proposed method significantly reduces the data capture process. The advancements in camera and software technologies have made it possible to acquire rapid and accurate 3D models of underground excavations that can be used as a source of rock mass data. Our results demonstrate that photogrammetry is a robust approach for underground rock mass inspection and remote mapping.

Photogrammetric scanning can be employed for the digitization of underground spaces, for example for remote mapping, visualization, or training purposes. However, such a technique requires capturing many photos, which can be laborious and time-consuming. Previous research has demonstrated that the acquisition time can be reduced by capturing the data with multiple lenses or devices at the same time. Therefore, this paper demonstrates a method for rapid scanning of hard rock tunnels using Structure-from-Motion (SfM) photogrammetry and a 360-degree camera. The test was performed in the Underground Research Laboratory of Aalto University (URLA). The tunnel is located in granitic rocks at a depth of 20 m below the Otaniemi campus in Espoo, Finland. A 10 m long and 3.5 m high tunnel section with exposed rock was selected for this study. Photos were captured using the 360-degree camera from 27 locations and 3D models were reconstructed using SfM photogrammetry. The accuracy, speed, and resolution of the 3D models were measured and compared with models scanned with a digital single-lens reflex (DSLR) camera. The results show that the data capture process with a 360-degree camera is 6x faster compared to a conventional camera. In addition, the orientation of discontinuities was measured remotely from the 3D model and the digitally obtained values matched the manual compass measurements. Even though the quality of the 360-degree camerabased 3D model was visually inferior compared to the DSLR model, the point cloud had sufficient accuracy and resolution for semi-automatic discontinuity measurements. The quality of the models can be improved by combining 360-degree and DSLR photos which result in a point cloud with 3x higher resolution and 2x higher accuracy. The results demonstrated that 360-degree cameras can be used for the rapid digitization of underground tunnels.

Remote sensing methods, for example, photogrammetry and laser scanning can be employed to scan rock masses by digitizing underground spaces or slopes. To reconstruct a 3D model by photogrammetry, plenty of photos should be captured. This process is time-consuming and can be dangerous when the rock mass is unstable. Therefore, rapid capturing methods are needed to reduce the acquisition time. This can be achieved with LiDAR scanners that capture a 3D point cloud with a high-speed pulsed laser beam. However, the cost of laser scanners is high, which limits their usability. Apple’s iPhone 12 Pro Max smartphone is equipped with a LiDAR sensor and is much cheaper than conventional laser scanners. Several mobile applications for 3D models using the smartphone Lidar have been developed, making the scanning process easy. Therefore, smartphones can be used for rapid scanning of unstable surfaces of tunnels and slopes. In this study, 3D point clouds (3DPC) of a tunnel wall of the Underground Research Laboratory of Aalto University (URLA) are obtained by a high-resolution digital camera and smartphone LiDAR. The models are analyzed and compared. The results show the quality of the smartphone LiDAR sensor is adequate for generating 3D models of underground spaces.

Characterization of fluid flow through rough fractures is an important issue in designing underground excavations, such as nuclear repositories or geothermal applications. Fluid flow could be influenced by several parameters such as contact areas, aperture, hydraulic and mechanical conditions. Contact area and aperture could be two crucial geometrical factors which control hydraulic and mechanical behaviors of fractures. These factors are rarely isotropic, and anisotropy is observed in different directions. In this research, photogrammetry, as a high precision method, was used to analyze morphology of a tensile fracture induced in granite. Experimental and numerical stress-flow tests on rock fracture were conducted in two different directions with diverse normal stresses and water pressures. Analyzing the regenerated 3D model of the fracture and hydromechanical tests predicts the anisotropy in flow rates in different directions. Numerical and experimental results are well fitted particularly in low-stress conditions. The obtained results show that anisotropy affects permeability since outlet flow rates in the different directions with the same initial water pressures differ by 7 % in experiments and 4% in numerical modeling.

Rock mass quality mapping is essential in rock engineering and mining projects. However, the current manual mapping approach and its teaching are restricted due to the dangerous nature of work near rock walls and the constraints of resources. Therefore, a virtual reality learning system for teaching remote mapping of rock mass quality was developed at Aalto University. Two rock wall sections of an underground tunnel and a roadside rock-cut were scanned using photogrammetry and imported as high-resolution textured 3D models. The user wears a head-mounted display and performs mapping using a pointing device. The system collects the measurements automatically and assists the user in rock mass mapping. Along with the development of the system, qualitative research was conducted to evaluate user performance in a gamified learning system. The results demonstrate that with proper game elements implemented, the learning system can be used to steer student behaviour towards the target range. Once set up, the VR system is a tireless, user-paced aid in training and teaching.

An accurate understanding of jointed rock mass behavior is important in many applications ranging from deep geological disposal of nuclear waste to deep mining to urban geoengineering projects. The roughness of rock fractures and the matching of the fracture surfaces are the key contributors to the shear strength of rock fractures. In this research, push shear tests with three normal stress levels of 3.6, 6.0, and 8.5 kPa were conducted with two granite samples with artificially induced well-matching tensile fractures with sizes of 500 mm × 250 mm and 1000 mm × 500 mm. The large sample reached on average a -60 % weaker peak shear stress than the medium-sized sample, and a strong negative scale effect was observed in the peak shear strength. The roughness of the surfaces was measured using a profilometer and photogrammetry. The scale-corrected profilometer-based method (JRC) underestimates the peak friction angle for the medium-sized slabs by -27 % for the medium sample and -9 % for the large sample. The photogrammetry-based (Z’2) method produces an estimate with -7% (medium) and +12 % (large) errors. The photogrammetry-based Z’2 is an objective method that consistently produces usable estimates for the JRC and peak friction angle.

SYNOPSIS Underground mining gives rise to geotechnical hazards. A formal geotechnical risk assessment can help to forecast and mitigate these hazards. Frequentist probability methods can be used when the hazard does not have many variables and a lot of data is available. However, often there is not enough data for probability distributions, such as in the case of new projects. The risk assessment is often subjective and qualitative, based on expert judgement. The purpose of this research is to present the use of Bayesian networks (BNs) as an alternative to existing risk assessment methods in underground mines by combining expert knowledge with data as it becomes available. Roof fall frequency forecasting using parameter learning is demonstrated with 1141 sets of roof fall data across 12 coal mines in the USA. The prediction is nearly identical for individual mines, but when multiple mines are evaluated it is difficult to find a single best fit distribution for annual roof fall frequency. The BN approach with TNormal distribution was twice as likely to fit the observed data compared to the Poisson distribution assumed in the past. A hybrid approach using BN combining multiple probability distribution curves from historical data to predict annual roof fall is proposed. The BN models can account for variability for multiple parameters without increasing the complexity of the calculation. BNs can work with varying amounts of data, which makes them a good tool for real-time risk assessment in mines. Keywords: Bayesian network; expert opinion models; geotechnical risk; incident forecasting; parameter learning; roof fall risk.

Passageways cut through rock might be subjected to rockfalls. If a falling rock reaches the road area, the consequences can be disastrous. The traditional rockfall risk assessment method and risk mitigation are based on on-site investigations performed by a geologist or a rock engineer. The parameters resulting from the investigation, such as discontinuities, orientations and spacings, potential rockfall initiation locations, slope geometry, and ditch profile, are either measured or estimated. We propose a photogrammetry-based method for estimating the probability of failure for rockfall. Several photographs of the rock-cut are taken, and a 3D geometry is computed using photogrammetry. This model already allows remote visual inspection of the site. The information about joint planes can be discovered semiautomatically from the point cloud. Next, the probability of rockfall reaching the road area is computed using probabilistic kinematic analysis on the geometry extracted using photogrammetry. The results can be used to define the rockfall probability for each rock-cut. Furthermore, the results can be used to determine the appropriate rockfall risk mitigation actions for each rock-cut.

The knowledge of geometrical properties of discontinuities is of crucial importance in the rock mass characterisation process. Recent advances in photogrammetry allow for an easy digitisation procedure of rock surfaces so that digital 3D models can be used for remote site characterisation. This paper presents a methodology to digitise tunnel rock surfaces using Structure from Motion digital photogrammetry for remote measurements of discontinuities. The proposed method is applied on a 12 m long and 4 m high tunnel section of an underground research tunnel at Aalto University in Finland, which is scanned using Canon 5Ds R DSLR camera and Canon 14 mm f/2.8 and 35 mm f/1.4 lenses. The photos are then processed in commercially available photogrammetric software – RealityCapture. As a result, a high-resolution 3D point cloud of the tunnel wall is produced. The point cloud is used for semi-automatic measurements of fracture orientations. In addition, a digital twin of the tunnel section with photorealistic surface texture is created and implemented into virtual reality (VR) system – Virtual Underground Training Environment (VUTE) developed for training of rock mass characterisation. The VUTE system enables remote visual inspection of the rock surface and virtual measurements of the orientation of discontinuities with designated virtual tools. The semi-automatic measurements extracted from the 3D point cloud using a discontinuity extractor software are compared with measurements performed in VR as well as with manual measurements performed in the tunnel. The results demonstrate that all three mapping methods identify three major joint sets with analogous orientations. The automatic fracture mapping method achieves the highest density of the measurements, allows repeatability, and enables other parameters to be extracted automatically, such as persistence and spacing of the discontinuities. This confirms the advantage of automatic analysis of discontinuities on 3D point clouds of tunnel rock surface digitised using photogrammetry.

Rock stress is causing unwanted deformations of deep underground spaces. Large deformations increase the risk of failure. The underground excavation causes rock stress changes in the surrounding rock mass, and the resulting deformations can be measured. In this paper, we present a method to monitor stress changes in the rock mass using rebar rock bolts instrumented with strain gauges to track the stress within the bolt. Next to that, we describe in-situ testing of this method using heating-induced stress in a natural underground environment. The heating experiment aims to create stress changes using rope heaters inserted into the rock mass and located symmetrically around a single instrumented rock bolt. The heat flux induced to the rock mass leads to volume expansion. The restricted thermal expansion causes an increase in the internal rock stress conditions. These conditions create a strain that can be measured and back-calculated as the rock stress change. The instrumented rock bolt and testing setup were installed in the Underground Research Laboratory located in a granitic rock below the Aalto University campus. The single bolt experiment demonstrates how instrumented rock bolts could monitor the changes in the rock mass stress state. The system can be used as a part of a real-time rock stress monitoring system in mining and rock engineering projects. The final part of the paper describes how this monitoring system can positively affect geotechnical risk management and increase the overall safety of underground construction.

The term extended reality (XR) refers to a family of technologies that cover Virtual Reality (VR), Augmented Reality (AR), and Mixed Reality (MR). The main benefit of XR is that it can offer a new viewpoint on the surrounding environment by augmenting it with digital data and visualizations. Recent developments of XR enable its deployment for rock engineering applications, including underground tunnels. In this paper, we demonstrate two cases of the use of XR in an underground tunnel to display spatial information on the tunnel surface. One of the tunnels in the Underground Research Laboratory of Aalto University (URLA) was digitized using Structure-from-motion (SfM) photogrammetry. As a result, a high-resolution 3D point cloud and textured model of the tunnel were created. Next, the rock joint planes were obtained semi-automatically from the digitized rock surfaces. The results are then represented in their actual positions in the tunnel geometry. In the first case, we used VR to display the rock joint planes on the textured model of the tunnel. In the second case, the data was displayed in real-time in tunnel conditions through a mobile device. The results demonstrate that XR technology can be successfully used in underground construction to digitize the workplace and provide a new perspective on the work environment, which can potentially lead to an increase in safety and productivity.

Deep mining, driven by the increasing need of the sustainable use of mineral resources, yields a chance to exploit untapped resources. Nevertheless, large depths remain challenging and complex environment, posing geotechnical risks such as stress driven damage. The violent damage mechanisms in deep mines are spalling and strainburst in their most severe forms. Real-time monitoring can not only assist in preventing a failure, but can also assist in post failure mitigations. It can help identify the possible systemic failure of adjacent areas and can therefore help in evacuating people and machinery from these areas. The long-term goal is to develop a real-time risk management concept for intelligent deep mines. The objective of this paper is to summarize the outcomes of I 2 Mine and DynaMine, formulate a risk concept suitable for real-time analysis and to produce a tangible measure of the risk levels. In this paper the Fault Tree – Event Tree methodology is proposed and an example is worked out using strainburst as an example risk case. The proposed methodology seems to work well and using a scenario with both property damage and ore loss, the risk expressed as financial consequences multiplied with probability drops from € 88,000 to € 11,000 corresponding to a - 80% reduction in risk. The financial consequences together with the associated risk level can be expressed visually using a modified FN graph with financial loss on x-axis and probability on the y-axis. The developed geotechnical risk management concept suits the need of semi-automated or fully automated risk management. It would fit well in the analysis stage of the raw data and would produce a stress state change, which could be used as input in the risk management chain for intelligent deep mines.

With increasing pressure to reduce the fraction of energy coming from fossil fuels, there is an increased need for research into feasible and sustainable energy sources, such as solar energy. The problem with solar energy is the mismatch between supply and demand, and so the energy needs to be stored. This research paper is a part of the project titled “Tackling the Challenges of a Solar-Community Concept in High Latitudes”, and aims in helping to design a thermal energy storage system for southern Finland that is economically feasible and has a high performance. For this purpose, a back-calculation of the underground thermal energy storage (UTES) of the Kerava Solar Village was performed. The primary objective was to calibrate the numerical models to be used in an optimisation by quantifying the thermal properties of the surrounding granite and soil. The UTES of the Kerava Solar Village consisted of a rock pit filled with water and two surrounding rings of boreholes. COMSOL Multiphysics 5.2® was used to create a model in which the temperature of the rock pit was used as the heat source and the heat propagation through the surrounding rock as the output to which the measured data was compared. The best replication of the temperature inside the rock near the surface was achieved with a conductivity of 2.8 and 1.0 W/(m·K) for granite and soil respectively. When looking at the deeper sections, the best fit was obtained for a conductivity of 5.5 and 1.0 W/(m·K) for granite and soil respectively. These results are conflicting, and outside the realistic range for granite. The strange behaviour of the measured isotherms could be explained by a presence of an additional heat source in the ground originating from a leakage of hot water from the tank into surrounding rocks. The critical issue identified in this study was the lack of data. All the parameters of the system, such as the geology, hydrology, and detailed technical drawings, but also the temperature distribution inside the heat source, and heat storage medium need to be known for back-calculation study to be successful.

Stope collapse is a common form of accident resulting in property loss and bodily harm in mines. There are several methods to carry out risk assessment for stope collapse incident in an underground mine. This paper presents an alternate method to determine stope collapse probability using Bayesian belief networks. The alternate methodology is designed to replace a subjective risk assessment process in a metal mine in Finland. First, the stope collapse failure mechanism specific to the underground mine was established by carrying out interviews with stake holders in the underground mine. These failure modes have been mapped using Bayesian network with the use of expert opinion. The expert opinions were obtained from the interviews and their correlation and interdependencies have been defined. Use of continuous data obtained from site instrumentation in the Bayesian network has been discussed to validate the expert opinion model and to create a near real-time risk monitoring system. Updating of failure probabilities using new evidence has been discussed using a ‘what-if’ scenario analysis and use of backward inference to carry out incident investigation in the event of a failure has been described. The paper further elaborates on how Bayesian modelling for risk assessment can be incorporated in mining to justify mitigation measures and use this as a decision-making tool. When combined with existing data collection systems in the mine, this can form the backbone for a real-time risk management system.

Seasonal storage of solar thermal energy is an attractive way to utilise the underground space to increase the share of renewables and tackle the global challenge of climate change. One of the methods to store the solar energy is the borehole thermal energy storage (BTES), where the thermal energy is stored in the rock mass using borehole heat exchangers. This study presents preliminary results of numerical predictions for an in situ experiment of underground thermal energy storage in the research tunnel under Otaniemi campus. The in-situ experiment site consists of two horizontal boreholes of 5 m length drilled into granitic rock. One borehole is equipped with a single U-tube heat exchanger, and the hot water is circulated through it to heat up the rocks, while the second hole is used for temperature measurement of the rock. The in situ experiment set-up is modelled numerically using finite element method to investigate the influencing factors and predict its long-term thermal performance. The three-dimensional problem is solved with the transient heat conduction equations and the temperature distribution in the subsurface is obtained during 21 days of operation. A parametric study is performed to find the optimal operating conditions. The results of the numerical predictions are used for a detailed plan of the experiment. The simulated results will be later compared to the measured values obtained in the experiment.

An in situ concrete spalling experiment will be carried out in the ONKALO rock characterization facility. The purpose is to establish the failure strength of a thin concrete liner on prestressed rock surface, when the stress states in both rock and concrete are increased by heating. A cylindrical hole 1.5 m in diameter and 7.2 m in depth is reinforced with a 40 mm thin concrete liner from level −3 m down. Eight 6 m long 4 kW electrical heaters are installed around the hole 1 m away. The experiment setup is described and results from predictive numerical modelling are shown. Elastoplastic modelling using the Ottosen failure criterion predicts damage initiation on week 5 and the concrete ultimate strain limit of 0.0035 is exceeded on week 10. The support pressure generated by the liner is 3.2 MPa and the tangential stress of rock is reduced by −33%. In 2D fracture mechanical simulations, the support pressure is 3 MPa and small localized damage occurs after week 3 and damage process slowly continues during week 9 of the heating period. In conclusion, external heating is a potent way of inducing damage and thin concrete liner significantly reduces the amount of damage.

The global challenge of climate change is urging for renewable energy sources to reduce greenhouse gas emissions. One of the applications of renewable energy is the solar district heating plant, which uses solar heat for space heating on a community scale. Seasonal storage of solar heat is crucial in solar district heating plants as a solution to the mismatch between the energy supply and demand. This is especially important in countries located in high latitudes with high levels of solar insolation and low heating demand in the summer, and low sun insolation and high heating demand in the winter time. This study investigates the selection of the most feasible method for seasonal storage of solar heat at high latitudes. The aim is to identify the key aspects of method selection and design of underground solar heat storage. Practices of underground thermal energy storage in Finland and other countries with similar ground conditions are reviewed. Five heat storage methods are evaluated based on their efficiency, cost, construction method, and suitability for typical ground conditions in Finland. The available methods of seasonal heat storage are compared, and the most promising method for solar heat storage in Finland is proposed. In addition, the potential provided by a combination of two or more methods is examined. The borehole storage method is proposed for storing solar heat in Finland. The combined method with a rock pit used for short-term heat storage and boreholes for long term storage is also an attractive and technically feasible option for Finnish ground conditions.

For low stress mining and civil engineering projects, slope stability is an essential part of safety and financial considerations. While large-scale stability can be modelled using equivalent rock mass properties, at smaller scale the local variations become significant and failure along the fracture planes is possible. The relevant boundary condition for low stress conditions is the Constant Normal Load (CNL), which allows for dilatation to occur. For deep mines the corresponding condition is the Constant Normal Stiffness, which restricts the dilatation. When dilatation is supressed the normal load is increased. This may lead to shearing of the asperities. If both the vertical and horizontal displacement are recorded during CNL testing, the dilatation may be calculated and numerically removed to provide a CNS estimate. In this paper three rock joint samples from the Siilinjärvi open pit mine were tested in a CNL shear box using displacement resetting at three different low normal loads. Profilometer and photogrammetry were used to measure the roughness of the surfaces. The results show poor match between the expected behaviour and observations. One possible cause is the reduced matedness often associated with natural near-surface rock joints. The potential weaknesses of the method are discussed and future research topics are suggested.

For mining and civil engineering projects rock slope stability is an essential part of safety and financial considerations. While large-scale stability can be simulated using rock mass properties, at smaller scale local variations in rock properties become significant and failure purely along discontinuities is possible. Plane failures, wedging and rockfall are common occurrences at this scale. These are often prevented by bolting or shotcrete support. For temporary slopes such support measures can be costly, and an ability to simulate possible failures along discontinuity planes becomes useful for evaluation of support necessity. Conventional methods for evaluating rock mass properties require making assumptions for scale effect in upscaling for an effective slope scale. The scale effect is generally considered to be negative, while some studies show positive or no scale effect. Deriving parameters to elaborately represent mechanical properties of rock mass in a scale of a mining project would require conducting a large scale in-situ test. Representativeness of one test for a large region of interest is questionable. Photogrammetric recording of rock joint surfaces aims to automate the obtaining of rock joint roughness without the need for manual sampling and costly laboratory experiments. Measurements carried out manually using a profilometer are compared to results obtained with photogrammetry without human interaction. The results are compared to tilt table tests to obtain a ratio between the natural roughness to profiled roughness. This ratio may be interpreted as a measure of how well the joint surfaces match. The photogrammetric JRC values may be used to predict the strength of rock joints under low stress conditions, where dilatation is not prevented. Finally discussion is given concerning the applicability of the method and the need for future research.

During the operation of nuclear waste disposal facilities, some sprayed concrete reinforced underground spaces will be in use for approximately 100 years. During this time of use, the local stress regime will be altered by the radioactive decay heat. The change in the stress state will impose high demands on sprayed concrete, as it may suffer stress damage or lose its adhesion to the rock surface. It is also unclear what kind of support pressure the sprayed concrete layer will apply to the rock. To investigate this, an in situ experiment is planned in the ONKALO underground rock characterization facility at Olkiluoto, Finland. A vertical experimental hole will be concreted, and the surrounding rock mass will be instrumented with heat sources, in order to simulate an increase in the surrounding stress field. The experiment is instrumented with an acoustic emission system for the observation of rock failure and temperature, as well as strain gauges to observe the thermo-mechanical interactive behaviour of the concrete and rock at several levels, in both rock and concrete. A thermo-mechanical fracture mechanics study is necessary for the prediction of the damage before the experiment, in order to plan the experiment and instrumentation, and for generating a proper prediction/outcome study due to the special nature of the in situ experiment. The prediction of acoustic emission patterns is made by Fracod 2D and the model later compared to the actual observed acoustic emissions. The fracture mechanics model will be compared to a COMSOL Multiphysics 3D model to study the geometrical effects along the hole axis.

VK: T20703

VK: T20703

VK: T20703 Yield-Line Theory (YLT) is an upper bound method for determining the bending capacity of a thin ductile slab. YLT has been shown to overestimate the flexural capacity of sprayed concrete slabs in some cases (e.g. Uotinen et al. 2013). In this paper, the EFNARC three point bending test on square panel with notch is evaluated using the original YLT, modified YLT and a fracture mechanics approach, and compared to a finite element solution. A small, 20 sample, comparative testing campaign is planned to be carried out in Aalto University in fall 2014. The emphasis is on the cracking capacity of the sprayed concrete, as cracked structures are not accepted and already require renovation. The solutions for each approach are shown and precomputed for the selected C35/45 comparison concrete strength class. The notched slab test was published in 2011 and not many cases are yet available. Comparison of the predictions to two known cases is shown. For future research, we suggest further modifications to the YLT method to represent the structural behaviour more accurately. One approach is to apply the load in steps and calculate the corresponding moment line pattern separately for each load stage. Second approach is to modify the line moment equation to reflect the semi-ductile behaviour, and to accommodate the effect of steel or polymer fibres. The third approach is to incorporate crack growth energy directly into the virtual work equations.

VK: T20703 A thermally induced shotcrete spalling in-situ experiment will be carried out during 2013 in the ONKALO rock characterization facility on the west coast of Finland. In the technical areas of the planned spent nuclear fuel repository there will be shotcreted rock spaces which will be subjected to thermally induced deformations and stresses. In this heating experiment, we are attempting to establish the failure strength of shotcrete on a pre-stressed rock surface, when the stress state in both the rock and shotcrete are increased by heating. The in-situ strength can be used to evaluate the safety of the shotcreted structures. The interaction between the shotcrete and the rock mass will be observed as the rock approaches its strength limit. Posiva’s Olkiluoto Spalling Experiment niche is ideal for such an experiment due to the amount of supplementary data from preceding experiments. The area is already built, instrumented and contains running experiments. The test arrangement is described and a prediction of theexpected results is provided. Similar research has been carried out using fire-induced thermal actions, but this is the first test to use heaters in the surrounding rock mass in the sub-boiling thermal range.

Yield-Line Theory (YLT) has been in wide spread use since the 1960's. YLT allows determining of the upper-bound bending resistance of reinforced concrete slabs using the concept of virtual work. YLT can be used for two purposes in the design of sprayed concrete support: the determination of quality assurance demands for the sprayed concrete or in the design of adequate sprayed concrete layer thickness against a bending failure. The square slab energy absorption test (EN 14488-5) and the round panel flexural toughness test (ASTM C1550-12a) are used. Solutions for both tests are given and conversion equations are derived. Testing results produced during normal quality assurance testing process in Länsimetro project (Finland) are shown for comparison. Finally, the merits and drawbacks of the test types are discussed.

VK: T20703 The Eurocodes are a set of European design principles, rules, and guidance intended for the design of load carrying structures. The codes have been compiled by the CEN Technical Committee 250 (CEN/TC250). The intent of the Eurocodes is to unify the design methodology. Parallel use with existing national building codes is allowed during the transition period (2007–2010) to ensure a smooth transition and enough time to make the necessary changes. In Finland (and Sweden and Norway), there is no formal procedure on how to design rock spaces. The design is based on a designer’s expertise, experience, views, and specific procedures. The problem here is that identical initial data could generate very different results depending on the way the initial data is interpreted and which design methods are used. The Eurocodes do not explicitly state how to design rock spaces, but they define the minimum requirements on how to design structures. The Eurocodes are divided into 10 areas. Of these ten, only a part will affect how to design rock spaces. Eurocode 0 defines the main principles concerning the whole design process. Eurocode 1 defines the loads. Eurocode 2 defines the design of concrete structures (e.g. design of reinforced concrete structures, shotcrete, and grouted rebars). Eurocode 3 defines the design of steel structures (e.g. design of non-grouted bolts, steel columns, and pillars). Eurocode 7 defines the design of geostructures. Eurocode 8 would define the design against earthquakes, but it is not required in Finland, unless otherwise stated.

Ever deepening mines and deep nuclear waste disposal facilities with strict safety regulations face spalling problem that is not well understood. Spalling phenomenon occurs as a strong compressive pressure inducing crack growth behind excavated surface and buckling of thin rock slabs. In this paper we describe how sophisticated spalling prediction methods can be applied to determine adequate tunnel support design in Posiva’s ONKALO. The general methods and a case study are described. The results of different prediction methods are compared to achieve an understanding of outcome range and a comparative analysis. The main analysis method is state of the art Three-Dimensional Finite Element Method (3-D FEM). The 3-D FEM mesh density is enhanced with a control surface and its limits and optimization is discussed. The result validity is studied with Kirsch equations and with two-dimensional indirect boundary element program to examine the tangential boundary stress. Shaft shape and required support is studied for the design process. Also a statistical reference analysis was done using Monte Carlo Spalling –simulation developed in year 2009 by Derek Martin and Rolf Christiansson.

Opponent: Michael Staudt, Supervisor: prof. Mikael Rinne Shotcrete was invented in the 1900’s and first used in rock spaces in the 1930’s. The design of shotcrete is currently (2011) mainly based on empirical rules. This paper explores the feasibility of designing shotcrete structures according to the methods allowed in the Eurocodes. The shotcrete material parameters are derived according to the Eurocode and presented for shotcrete grades up to C50/60. The EFNARC panel test (EN 14488-5) and ASTM round panel test (C1550) are used in conjunction with the Yield Line Theory (YLT) to produce the cracking limit of the bending resistance. The shotcrete failure process and failure modes are described. Linear elastic theory is used to calculate the crack initiation capacity. The means on how to calculate the shotcrete capacity for the most common failure modes are presented. Finally, notes on how to apply these results into practical design work are given. Non

Characterization of Hydro-Mechanical (H-M) properties of rock fractures is the initial and important step in modeling of fully H-M coupled processes in fractured rock masses. Fluid flow in the fractured rock mass is an important aspect when evaluating the safety of geological disposal of high-level nuclear waste. Many attempts have been taken to measure and model fluid flow in rock fractures in different stress field conditions. However, still study about the scale effect of fracture properties and confinement stress on the conductivity of rough rock fractures remains a challenging topic of research. As a part of an ongoing research project about fluid flow modeling in fractured rock mass (RAKKA), and as an initial step one rock slab pair with sizes of 250 mm x 250 mm of Kuru grey granite halves was prepared. It has a horizontal mechanically induced tensile fracture. The surface roughness of the fracture was mapped using a conventional profilometer and structure-from-motion photogrammetry before each fluid flow test. The fractures were subjected to different normal stress and then fluid flow within the fractures was conducted linearly from edge to opposite edge with perpendicular edges sealed, and conductivity of the fractures under steady-state condition was measured. Then the test is repeated with all three sides open. The results show anisotropic behaviour in permeability. The diagonal components of the permeability matrix are significantly stress-dependent. Together the new fracture digitization method and the new three-way fluid flow test allow the contactless characterization of hydro-mechanical properties of rock fractures and the validation of the results.

Virtual reality (VR) can be used to enhance teaching in engineering education as it enables designing interactive and immersive exercises integrated with digitized learning spaces. In this paper, we demonstrate two VR learning systems related to rock engineering, geology and mining education developed at Aalto University, Finland. First is the Virtual Underground Training Environment created for the training of structural mapping and rock mass characterization. It consists of a photorealistic 3D model of the Underground Research Laboratory of Aalto University and virtual replicas of mapping tools. It was tested on students and the results demonstrated that training in VR reduces scatter in measured learning outcomes and increases the active learning time by +50%. The second VR learning system was developed for teaching students how to identify rocks and minerals. A collection of more than 100 rock and mineral specimens was digitized using photogrammetry and turned into a digital online learning asset. The twovirtual learning systems demonstrate that VR can be a powerful tool to enhance learning in engineering education. Besides the educational potential, the photogrammetric digital models generated for the VR learning systems can be used for remote inspection and rock mass characterization, visualization, and communication of multidimensional data.

The thermal heating caused by the deposition of spent nuclear fuel containers increases the in situ rock stress during disposal time. The thermal stress increase was modelled using thermo-mechanical modelling. The numerical codes used to establish the effects of heating on the in situ stress field are outlined, together with the rock mass parameters, in situ stress values, radiogenic temperatures and reinforcement structures. This is followed by a study of the temperature and stress evolution during the repository's operational period and the effect of the heating on the reinforcement structures. It is found that, during excavation, the maximum principal stress is concentrated at the transition areas where the excavation profile changes and that, due to the heating from the deposition of spent nuclear fuel, the maximum principal stress rises significantly in the tunnel arch area of NW/SW oriented central tunnels. However, it is predicted that the rock’s crack damage (CD, short term strength) value of 99 MPa will not be exceeded anywhere within the model. An additional study of the radiogenic heating effect on the brittle deformation zones is included. The main conclusion is that, despite deep reaching damage potential in all the load cases studied the currently designed and used reinforcement types and configurations (rock bolts, shotcrete) are capable of handling the dead weight of the damaged rock should this occur, with damage occurring on the shotcrete liner. The long term safety and stability of the repository during its lifetime can be guaranteed by perceiving the reinforcement strategy in two stages. Firstly, by installing the rock reinforcement to sustain the initial stresses and short term increases from the start of deposition with a monitoring programme in place. Secondly, by installing additional reinforcement, if found necessary through monitoring and observation of the underground facilities. In this way, the effect of any time dependent rock stress increase affecting the reinforcement structures can be observed, in addition to creep based damage, thus providing a better level of safety than a single stage design.

openaire: EC/FP7/280855/EU//I²Mine Underground mines rely on point stress measurements, which are limited both in time and in space.Developing a stress monitoring system that can provide real-time information about the surrounding rockmass stresses is seen as highly prospective. Mines could quantify the level of rock mechanical hazards and track stability of the excavations. A method for real-time stress change estimation was developed at Aalto University. The method uses strain measurements, which are obtained using extensometers and inverse calculation of stress change using superposition of unit stress responses. It was tested in Boliden’s Kylylahti mine. Aalto University developed guidelines for risk assessment in underground mines that can utilize real-time rock stress input in order to quantify the level of geotechnical hazards. The long-term goal is to develop a concept for real-time monitoring and risk assessment in underground mines. The objective of this paper is to summarize the preceding research and to investigate how the real-time in situ stress data can be used for real-time risk assessment and ground support optimisation in underground mines. The key concepts are introduced and the required changed to the process with real-time data are described. An example from Kylylahti mine is presented as an example use case. The current state, required changes, advantages and difficulties with the current approach are discussed. Finally, based on the observations, suggestions for future research are given.