Browsing by Author "Janiszewski, Mateusz"

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  • 3D dataset of a twisted bending-active beam element digitized using structure-from-motion photogrammetry
    (2024-06) Janiszewski, Mateusz; Elmas, Serenay; Markou, Athanasios A.; Jaaranen, Joonas; Filz, Günther H.
     Data Article
    The current work presents the generation of a comprehensive spatial dataset of a lightweight beam element composed of four twisted plywood strips, achieved through the application of Structure-from-Motion (SfM) - Multi-view Stereo (MVS) photogrammetry techniques in controlled laboratory conditions. The data collection process was meticulously conducted to ensure accuracy and precision, employing scale bars of varying lengths. The captured images were then processed using photogrammetric software, leading to the creation of point clouds, meshes, and texture files. These data files represent the 3D model of the beam at different mesh sizes (raw, high-poly, medium-poly, and low-poly), adding a high level of detail to the 3D visualization. The dataset holds significant reuse potential and offers essential resources for further studies in numerical modeling, simulations of complex structures, and training machine learning algorithms. This data can also serve as validation sets for emerging photogrammetry methods and form-finding techniques, especially ones involving large deformations and geometric nonlinearities, particularly within the structural engineering field.
  • Challenges of hydraulic stimulation in enhanced geothermal system
    (2018-04-22) Korhonen, Antti
     Insinööritieteiden korkeakoulu | Bachelor's thesis
  • Characterization of hydro-mechanical properties of rock fractures using steady state flow tests
    (2020-11-13) Uotinen, Lauri; Torkan, Masoud; Janiszewski, Mateusz; Baghbanan, Alireza; Nieminen, Ville; Rinne, Mikael
     A4 Artikkeli konferenssijulkaisussa
    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.
  • Comparison of camera equipment for photogrammetric digitization of hard rock tunnel faces
    (2021-05-17) Prittinen, Markus
     Insinööritieteiden korkeakoulu | Master's thesis
    It is important to have good data for making safe tunnel designs. An understanding of the prevailing discontinuities is crucial to evaluate the quality of the rock mass and reinforcement needs. Photogrammetry using Structure-from-Motion is a 3D-scanning technique from which one can make 3D representations of real-life objects using 2D-photos. The 3D-models allows for more automated and faster discontinuities mapping than traditional compass methods. The research location is the Underground Research Laboratory of Aalto University (URLA), which is a tunnel complex located in underneath Otaniemi campus at Aalto University in Espoo Southern Finland. The research questions are: What are the challenges in tunnel photogrammetry? What are the most efficient methods in capturing tunnel environments? Are 360- and action cameras a viable alternative to more traditional photogrammetry methods using DSLR cameras? Do the methods used produce 3D-models good enough for identifying rock futures and for doing measurements and discontinuity mapping? In this thesis different cameras are compared for Structure-from-Motion photogrammetry, a DSLR camera, a 360-camera, and a GoPro rig that was developed during the research. The GoPro rig combines four GoPro action cameras using a plastic frame and 3D-printed parts and can be used both handheld and on a tripod. An experiment is done using constraints for how close to an unsupported walls work can be done, to simulate a tunnel under construction. The accuracy, speed and resolution of each method is measured. The geometric accuracy is compared with measurements from a laser measurement tool. Traditional compass measurements of discontinuity sets are compared with measurements from 3D-models gathered, including semi-automated measurements of discontinuities in Discontinuity Set Extractor. The results show that out of the methods compared the DSLR method is most accurate and the 360-camera least accurate, yet each method produces a point cloud accurate enough for automatic discontinuity set measurements. Out of the methods tested the GoPro rig was proven to be both the fastest and cheapest method in acquiring images for photogrammetry.
  • Comprehensive Evaluation of ImageNet-Trained CNNs for Texture-Based Rock Classification
    (2024) Mandal, Dipendra J.; Deborah, Hilda; Tobing, Tabita L.; Janiszewski, Mateusz; Tanaka, James W.; Lawrance, Anna
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Texture perception plays a vital role in various fields, from computer vision to geology, influencing object recognition, image segmentation, and rock classification. Despite advances in convolutional neural networks (CNNs), their effectiveness in texture-based classification tasks, particularly in rock classification, still needs exploration. This paper addresses this gap by evaluating different CNN architectures using diverse publicly available texture datasets and custom datasets tailored for rock classification. We investigated the performance of 38 distinct models pre-trained on the ImageNet dataset, employing both transfer learning and fine-tuning techniques. The study highlights the efficacy of transfer learning in texture classification tasks and offers valuable perspectives on the performance of different networks on different datasets. We observe that while CNNs trained on datasets like ImageNet prioritize texture-based features, they face challenges in nuanced texture-to-texture classification tasks. Our findings underscore the need for further research to enhance CNNs' capabilities in texture analysis, particularly in the context of rock classification. Through this exploration, we contribute insights into the suitability of CNN architectures for rock texture classification, fostering advancements in both computer vision and geology.
  • Deep learning methods for underground deformation time-series prediction
    (2023-04-12) Ma, Enlin; Janiszewski, Mateusz; Torkan, Masoud
     A4 Artikkeli konferenssijulkaisussa
    Prediction is a vague concept that is why we need to conceptualize it specifically for underground deformation time-series data. For this impending issue, this paper employs an advanced deep learning model Bi-LSTM-AM to address it. The results show its applicability for practical engineering. The proposed model is compared with other basic deep learning models including long short-term memory (LSTM), Bi-LSTM, gated recurrent units (GRU), and temporal convolutional networks (TCN). These models cover the most common three forms of deep learning for time-series prediction: recurrent neural networks (RNN) and convolutional neural networks (CNN). This research is supposed to benefit the underground deformation time-series prediction.
  • Developing virtual learning environments for engineering education
    (2022-11-17) Paulomäki, Hanna; Janiszewski, Mateusz; Hirvonen, Inka; Järvinen, Mika
     A4 Artikkeli konferenssijulkaisussa
    The operating environment for engineers has changed in recent years (Vona et al., 2018; ILO, 2019). Energy transition driven by ecological crises creates a need to have a critical look into engineers’ skill sets and competencies. The renewable energy sector is one of the most significant ones in terms of new job opportunities and the development of new occupational profiles (ILO, 2019). At the same time, the transition to environmentally sustainable and socially just future creates a growing need for expertise that is different from the traditional technically focused competence profile. The project described in this presentation aims to establish best practices for the creation of digital learning environments in a cost-effective way that is easy to integrate with educational contents. We aim to make use of virtual reality-based learning, develop digital and engaging learning environments, and create a radical new opening to develop education and share best practices with other higher education institutions. The learning environment is known to have a significant impact on the success of learning. It is effective to practice skills in a real environment, but this is not always possible because it can be inaccessible or dangerous. For example, it is not possible or allowed to take 100+ students to a nacelle of a large wind turbine at the height of 150 m or in an underground thermal storage cave. Virtual site visits are also cheaper, reduce the need for traveling, and therefore, decrease CO2 emissions, and make learning flexible as the materials can be reached at any time convenient for the students. Virtual learning environments are recognized as viable tools to improve engineering education and training and have been developing rapidly in recent years (Wang et al. 2018, Hirvonen 2021). The use of virtual reality tools allows, for example, easy-to-understand visualisation and communication of complex spatial data (Janiszewski et al., 2021; Du et al., 2017). Virtual learning environments provide great opportunities, but they are challenging to create and require specialist knowledge of 3D scanning, VR development, and programming. The challenge is to integrate them with existing educational content. Educational contents of our project include development of showcases of virtual reality-based learning tools for effective teaching of engineering. Two virtual learning journeys will be demonstrated. One is related to renewable energy engineering. Rapid energy transition challenges us all, also energy engineering education. This requires whole new kinds of learning tools. We will showcase an onshore wind energy site. Along the virtual journey, the student is introduced to technical solutions as well as ecological and social sustainability considerations. The second educational content is about scaling-up existing virtual reality learning systems for rock engineering and engineering geology teaching developed as part of the Aalto Online Learning’s MIEDU, EDUROCK, and COVE pilots (Jastrzebski, 2017; Janiszewski et al., 2020a; Zhang, 2020). This knowledge can further be used to develop a demo on underground thermal energy storage. An example is a virtual rock and mineral database that has more than 100 samples digitised from the university’s collection (EDUROCK, 2019). Test results show that the use of this virtual material enhanced the learning outcomes by 20%. Finally, there will be an evaluation of the student experience and analyses of the pedagogical aspects done. A very important part of the project is to make sure that the tools and materials are pedagogically relevant and support the intended learning outcomes logically. The focus is on developing flexible and engaging teaching scenarios to achieve learning goals. Detailed workflow descriptions of the processes will be developed and published.
  • Development and testing of smart rock bolt for rock stress monitoring
    (2021-01-25) Mai, Walter
     Insinööritieteiden korkeakoulu | Master's thesis
    Rock stress often causes unwanted deformations of deep underground spaces and increases the risk of failures. The excavation procedures create changes in surrounding rock mass which can be analysed by in situ measurements. This thesis presents a new method to monitor the rock mass behaviour using smart rock bolt instrumented with strain sensors tracking and evaluating the stress level within the bolt. The development and assembling of the first smart rock bolt prototype are described in detail. The thesis also describes in-situ testing of this new monitoring prototype in a real underground environment. Two identical smart rock bolt prototypes were tested in the test tunnel of an underground research laboratory. The testing setup used two methods to test these prototypes; pull-out force and heat flux applied to the rock mass via rope heaters inserted into symmetrically located boreholes around the smart rock bolt. The temperature progress during the heating test was numerically modelled in advance. The correct functionality of heating test was verified in-situ using a borehole deformation monitoring tool developed for this purpose. The heat causes volume expansion of the rock material which simulates changes in the rock stress. This stress change creates measurable strain that can be back-calculated and presented as values of rock stress. The strain results from monitoring were analysed, cleaned from noise values and imported to REMOS code using rock stress estimation algorithm and modified for use of smart rock bolt. The algorithm requires strain responses on unit loading based on the impact of rock stress. To calculate strain responses, numerical modelling in 2D was used considering three independent cases of rock stress. The final results demonstrate changes in horizontal, vertical and shear rock stress induced by the testing method according to strain change measured by the smart rock bolt prototype.
  • Digitisation of hard rock tunnel for remote fracture mapping and virtual training environment
    (2020-11) Janiszewski, Mateusz; Uotinen, Lauri; Baghbanan, Alireza; Rinne, Mikael
     A4 Artikkeli konferenssijulkaisussa
    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.
  • Effective modelling of borehole solar thermal energy storage systems in high latitudes
    (2018-12-10) Janiszewski, Mateusz; Siren, Topias; Uotinen, Lauri Kalle Tapio; Oosterbaan, Harm; Rinne, Mikael
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Globally there is an increasing need to reduce the greenhouse gas emissions and increase the use of renewable sources of energy. The storage of solar thermal energy is a crucial aspect for implementing the solar energy for space heating in high latitudes, where solar insolation is high in summer and almost negligible in winter when the domestic heating demand is high. To use the solar heating during winter thermal energy storage is required. In this paper, equations representing the single U-tube heat exchanger are implemented in weak form edge elements in COMSOL Multiphysics (R) to speed up the calculation process for modelling of a borehole storage layout. Multiple borehole seasonal solar thermal energy storage scenarios are successfully simulated. After 5 years of operation, the most efficient simulated borehole pattern containing 168 borehole heat exchangers recovers 69% of the stored seasonal thermal energy and provides 971 MWh of thermal energy for heating in winter.
  • Empirical mode decomposition approach to simplify the fracture roughness for numerical models
    (2023-01-10) Ma, Enlin; Rinne, Mikael; Torkan, Masoud; Janiszewski, Mateusz
     A4 Artikkeli konferenssijulkaisussa
    The shear strength of natural, unfilled rock fractures is influenced by surface roughness. The surface curve of a fracture can be viewed as a waveform graph, and in general, it is of the characteristic that high-frequency represents the low amplitude (local variation) and low-frequency represents the high amplitude (general trend). In this work, the signal processing method, Empirical Mode Decomposition (EMD) was employed to decompose the original fracture surface scanned by photogrammetry to several frequency-dependent curves. Low-frequency curves were selected and composed as the element geometry while high-frequency curves were ignored and replaced by parameters related to the roughness in each surface element in Abaqus. The process of push-shear test is simulated using the simplified fracture curve, showing the geometry simplification by EMD can help model the shear failure of rock fractures.
  • Evaluation of induced seismicity risk in the Pyhäsalmi mine
    (2016-05) Janiszewski, Mateusz; Rinne, Mikael
     A4 Artikkeli konferenssijulkaisussa
    A Recent increase of induced seismicity and high rock stresses in the Pyhäsalmi mine have proven the need for an analysis of the seismic data and prediction of hazard. Seismic events and other influencing factors are analysed to forecast and quantify the level of induced seismicity risk in the Pyhäsalmi mine. The expected maximum event size is found by clustering seismic data using the Quality Threshold and Single Linkage clustering algorithms and applying the Gutenberg-Richter’s frequency-magnitude relationship. Induced seismicity risk is assessed using the Quantitative Seismic Hazard and Risk Assessment Framework. The potential for induced seismicity is calculated as a function of the maximum local seismic magnitude, rock stresses and strength, local geology, excavation geometry, and ground support capacity. The exposure to the hazard is taken into account in order to quantify the level of risk. The assessment is performed on three mining levels at about 1.2 km depth, which are divided into assessment zones. Most of the assessment zones have a low seismic risk and only a few have an elevated potential of rockburst. The highest risk is found along the northern contact zone of ore and waste rock, adjacent to important mine infrastructure. The critical areas are identified and installation of ground support with increased dynamic capacity is recommended as a risk mitigation strategy.
  • Evaluation of methods for stope design in mining and potential of improvement by pre-investigations
    (2019-10-21) Pontow, Sebastian
     Insinööritieteiden korkeakoulu | Master's thesis
    The importance of stope design for mine planning is considerable. Therefore, stope design and its challenges have been in the focus of research for the past 50 years. Empirical, numerical and analytical methods for stope design have been developed over the past decades in order to improve this process. This thesis is assessing which areas for improvement there still are and which problems are still only unsatisfactorily solved. After establishing background knowledge about the importance of stope design for mine planning and evaluating the factors influencing stope design, the focus is laid on the development of stope design methods in the past, as well as current research related to the topic, to create a comprehensive overview of recent and future developments. This is done by means of a literature review and research analysis. On the other side, the mining industry´s needs and challenges related to stope design are assessed, by means of survey, mine visit and interview. The insights gained in both parts are compared and checked for potential harmonies and disharmonies. Finally, from those conclusions practical recommendations for the GAGS-project are extracted and consecutively presented. In stope design research the focus and dominance of empirical methods has slowly shifted towards more research being conducted in the area of numerical and analytical methods. It can also be concluded that numerical methods and personal expertise are far more important for stope design within industry than commonly assumed. It was identified that in order to improve stope design, it is desired to increase the amount of geotechnical data acquired, the software improved, and stope design integrated within the general mine planning process. Additionally, interesting insights were gained by an in-depth analysis of survey responses, for example, the outstanding importance of the cut-off grade for stope design within gold mining operations. In order to allow for an optimal acceptance of novel geotechnical methods for stope design, the acquired data should be implementable into stope design within three days, preferably be compatible or implemented within a software and allow for stope design to be integrated into general mine planning. To promote the benefits a comprehensive scientific case-study demonstrating the realized benefits should be performed.
  • Feasibility of underground seasonal storage of solar heat in Finland
    (2016-09-29) Janiszewski, Mateusz; Kopaly, Antoni; Honkonen, Mikko; Kukkonen, Ilmo; Uotinen, Lauri; Siren, Topias; Rinne, Mikael
     A4 Artikkeli konferenssijulkaisussa
    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.
  • A Gamifed Rock Engineering Teaching System
    (2020) Zhang, Xiaoyun
     Perustieteiden korkeakoulu | Master's thesis
    This thesis addresses the lack of gamification in rock engineering educational applications. The goal of this thesis was to create an enjoyable and effective rock fracture mapping learning experience using virtual reality (VR) and gamification. The hypothesis is that gamification can improve the learning experience and learning outcomes of learners. A concrete output of this thesis is a gamified teaching system GRETS (Gamified Rock Engineering Teaching System). The system includes a teaching module of three concepts related to structural mapping and a gamified practical exercise module. In this thesis, the influence of gamification on the learning experience and learning outcomes was measured through a mixed-method user study. In the user study, a non-gamified rock engineering teaching system (NGRETS) was created as a controlled environment, and the learning experience of both systems was compared to measure the impact of gamification. According to the user study result, GRETS provided learners with an enjoyable learning experience, and their learning outcomes were improved. For instance, the accuracy index, which represents learners’ measurement accuracy, was doubled. Although the quantitative data is inconclusive due to various limitations, the thesis advances the gamification of rock engineering education and provides a novel example case that other gamification researchers, designers, and educators can build on.
  • Geotechnical risk assessment in the Pyhäsalmi mine with a focus on seismic risk
    (2014-08-25) Janiszewski, Mateusz
     Insinööritieteiden korkeakoulu | Master's thesis
    Due to a constant depletion of shallower deposits underground mining is pushing production to larger depths resulting in more difficult ground conditions and an increase of rock stresses. Mining at larger depth effects in an increase in seismic activity, therefore seismic risk is becoming more important and requires special attention. This necessitates development of frameworks and guidelines to tackle those risks more efficiently. The scope of this study was to apply and test the Geotechnical Risk Assessment guideline for underground mines developed at Aalto University as part of the project: Innovative Technologies and Concepts for the Intelligent Deep Mine of the Future (I2mine), work package 3 - “Rock mechanics and ground control”, under the 7th framework of the European Union. The goal was to use seismic monitoring data from the Pyhäsalmi mine in order to quantify the seismic risk, using proposed guideline as a framework for evaluation. Furthermore, the research was aimed to give answers on: what is the applicability of the guideline, what are the main issues encountered during its usage and how to improve it. Geotechnical Hazard Potential was evaluated using a proposed methodology. Next, seismic risk in the Pyhäsalmi mine was assessed. Seismic events from the database were clustered into logical groups in order to speed up the analysis. Then, the maximum predicted size of a seismic event was found for each cluster group. Seismic risk was assessed based on the largest possible seismic event attributable with a particular damage that is expected. The final risk was evaluated using two methodologies: one that is currently used in the mining industry and second under the development. The level of seismic risk in the Pyhäsalmi mine was found to be low. The biggest risk was found in areas located at the northern ore-waste contact zone. Installation of additional ground support was recommended in order to lower the risk. The Geotechnical Risk Assessment guideline was found to be suitable framework for risk assessment purposes, which supports in selection of appropriate assessment approach and aids in selection of tools that are used throughout the evaluation. Its applicability was found to be high, however minor changes were recommended in order to use its full functionality.
  • Geotechnical risk management concept for intelligent deep mines
    (2017) Mishra, Ritesh; Janiszewski, Mateusz; Uotinen, Lauri; Szydlowska, Martyna; Siren, Topias; Rinne, Mikael
     A4 Artikkeli konferenssijulkaisussa
    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 is 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 I2Mine 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 $128,621 to $25,766 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.
  • High-resolution photogrammetry to measure physical aperture of two separated rock fracture surfaces
    (2024-08) Torkan, Masoud; Janiszewski, Mateusz; Uotinen, Lauri; Baghbanan, Alireza; Rinne, Mikael
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Photogrammetry, reconstructing three-dimensional (3D) models from overlapping two-dimensional (2D) photos, finds application in rock mechanics and rock engineering to extract geometrical details of reconstructed objects, for example rock fractures. Fracture properties are important for determining the mechanical stability, permeability, strength, and shear behavior of the rock mass. Photogrammetry can be used to reconstruct detailed 3D models of two separated rock fracture surfaces to characterize fracture roughness and physical aperture, which controls the fluid flow, hydromechanical and shear behavior of the rock mass. This research aimed to determine the optimal number of scale bars required to produce high-precision 3D models of a fracture surface. A workflow has been developed to define the physical aperture of a fracture using photogrammetry. Three blocks of Kuru granite (25 cm × 25 cm × 10 cm) with an artificially induced fracture, were investigated. For scaling 3D models, 321 markers were used as ground control points (GCPs) with predefined distances on each block. When the samples were well-matched in their original positions, the entire block was photographed. Coordinate data of the GCPs were extracted from the 3D model of the blocks. Each half was surveyed separately and georeferenced by GCPs and merged into the same coordinate system. Two fracture surfaces were extracted from the 3D models and the vertical distance between the two surfaces was digitally calculated as physical aperture. Accuracy assessment of the photogrammetric reconstruction showed a 20–30 μm digital control distance accuracy when compared to known distances defined between markers. To attain this accuracy, the study found that at least 200 scale bars were required. Furthermore, photogrammetry was employed to measure changes in aperture under normal stresses. The results obtained from this approach were found to be in good agreement with those obtained using linear variable displacement transducers (LVDTs), with differences ranging from 1 μm to 8 μm.
  • Hydraulically fractured hard rock aquifer for seasonal storage of solar thermal energy
    (2018-05-15) Janiszewski, Mateusz; Shen, Baotang; Rinne, Mikael
     A4 Artikkeli konferenssijulkaisussa
    The intermittent nature of solar thermal energy derives from its oversupply during the low season and undersupply during the peak season. The solution is to accumulate and store the surplus energy that can be used in times of high demand and low supply. The HYDROCK concept is a method developed for seasonal heat storage in artificially fractured bedrock. This study aims to investigate the rock fracturing process in the construction of hydraulically fractured hard rock aquifer for seasonal storage of thermal energy. The primary objective of this study is to perform a sensitivity analysis of numerical simulations of rock fracturing processes that are taking place during the development of artificially fractured heat storage in hard rocks. Coupled hydro-mechanical numerical models are generated using rock fracture mechanics code FRACOD2D. The sensitivity of critical parameters is presented, and all relevant influencing factors are investigated. Suggestions for practical applications of HYDROCK are given.
  • In Situ Experiment and Numerical Model Validation of a Borehole Heat Exchanger in Shallow Hard Crystalline Rock
    (2018-04-17) Janiszewski, Mateusz; Caballero Hernandez, Enrique; Siren, Topias; Uotinen, Lauri; Kukkonen, Ilmo; Rinne, Mikael
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Accurate and fast numerical modelling of the borehole heat exchanger (BHE) is required for simulation of long-term thermal energy storage in rocks using boreholes. The goal of this study was to conduct an in situ experiment to validate the proposed numerical modelling approach. In the experiment, hot water was circulated for 21 days through a single U-tube BHE installed in an underground research tunnel located at a shallow depth in crystalline rock. The results of the simulations using the proposed model were validated against the measurements. The numerical model simulated the BHE’s behaviour accurately and compared well with two other modelling approaches from the literature. The model is capable of replicating the complex geometrical arrangement of the BHE and is considered to be more appropriate for simulations of BHE systems with complex geometries. The results of the sensitivity analysis of the proposed model have shown that low thermal conductivity, high density, and high heat capacity of rock are essential for maximising the storage efficiency of a borehole thermal energy storage system. Other characteristics of BHEs, such as a high thermal conductivity of the grout, a large radius of the pipe, and a large distance between the pipes, are also preferred for maximising efficiency.