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Publications (4 of 4) Show all publications
Zirgulis, G., Javadi, H., Arun Chaudhari, O., Ghafar, A. N., Fontana, P., Sanner, B., . . . Shuster, M. (2023). Temperature evolution around four laboratory-scale borehole heat exchangers grouted with phase change materials subjected to heating–cooling cycles: An experimental study. Journal of Energy Storage, 74, Article ID 109302.
Open this publication in new window or tab >>Temperature evolution around four laboratory-scale borehole heat exchangers grouted with phase change materials subjected to heating–cooling cycles: An experimental study
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2023 (English)In: Journal of Energy Storage, ISSN 2352-152X, E-ISSN 2352-1538, Vol. 74, article id 109302Article in journal (Refereed) Published
Abstract [en]

This article presents the experimental results from a unique laboratory test-setup used to comparative study of heat transfer conditions in borehole heat exchangers with different grouts under a controlled environment. The work was part of a larger, EU-funded project on advanced materials for borehole heat exchangers pipes and grout, GEOCOND. Four grout columns with different formulations were cast and tested under cyclic heating and cooling. One grout column was cast using high thermal conductivity grout; two columns were cast from high thermal conductivity grout with microencapsulated phase change material (MC-PCM) and one with shape-stabilised phase-change material (SS-PCM). The objective of the test was to comparatively evaluate performance of the borehole heat exchanger under a cyclic temperature regime and to investigate if the selected phase change materials (PCM) embedded in grout can be activated by cyclic heating and function steadily. Twenty-five heating-cooling cycles were performed, each lasted 24 h. The results showed clear cooling delay in grouts containing PCM associated with the crystallization heat release. The cooling delay was better expressed in grouts with SS-PCM. The PCM related cooling delay was stable throughout all the cycling in SS-PCM containing grouts, however, the effect vanished in grouts with MC-PCM. © 2023 The Authors

Place, publisher, year, edition, pages
Elsevier Ltd, 2023
Keywords
Boreholes; Cooling; Geothermal energy; Grouting; Mortar; Thermal conductivity; Borehole heat exchangers; Cyclic heating; Heating-cooling cycle; High thermal conductivity; High thermal conductivity grout; Laboratory test; Shallow geothermal energies; Shape stabilized phase change material; Temperature evolution; Test setups; Phase change materials
National Category
Energy Engineering
Identifiers
urn:nbn:se:ri:diva-67699 (URN)10.1016/j.est.2023.109302 (DOI)2-s2.0-85174685922 (Scopus ID)
Funder
EU, Horizon 2020, 727583
Note

This work received funding from the European Union's Horizon 2020 research and innovation programme [grant agreement number No 727583 ].

Available from: 2023-11-06 Created: 2023-11-06 Last updated: 2023-11-16Bibliographically approved
Zirgulis, G., Nejad Ghafar, A. & Arun Chaudhari, O. (2022). Development of dynamic grouting under laboratory and field conditions. Geomechanics and Tunneling, 15(5), 535-539
Open this publication in new window or tab >>Development of dynamic grouting under laboratory and field conditions
2022 (English)In: Geomechanics and Tunneling, ISSN 1865-7362, E-ISSN 1865-7389, Vol. 15, no 5, p. 535-539Article in journal (Refereed) Published
Abstract [en]

When it comes to underground structures, water ingress from the surrounding formations leads to several environmental, economic and sustainability issues. To obtain the sealing, the grouting of rock fractures is done. Today, in the grouting operations, which are commonly conducted in almost all the tunnel and subsurface infrastructure projects, the pressure applied is static. This type of applied pressure might be suitable for the large fracture apertures > 100 μm, but it has been acknowledged that it is difficult to obtain sufficient penetration through smaller apertures, where filtration of cement particles starts to occur. Research is already done to overcome this issue by applying dynamic grouting pressure instead of static. It was proved that this approach erodes the formed filter cakes and improves grout penetrability in fractures below 100 μm. This research focuses on low-frequency rectangular pressure impulse as an alternative to other methods. The goal is to improve grout spread in micro-fractures (especially in apertures < 70 μm). During the investigation, a prototype dynamic injection equipment was built and tested under laboratory conditions. The 4 m variable aperture long slot (VALS) was used in the experiments to simulate rock fractures. The test showed better grout penetrability using dynamic pressure approach. At the current time of writing this article, preparation works are done for field test of prototype equipment at SKB Hard Rock Laboratory (HRL) at Äspö, Sweden. 

Place, publisher, year, edition, pages
Ernst und Sohn, 2022
Keywords
Conventional tunneling, dynamic grouting, filtration erosion, grout penetrability, Grouting, Innovative procedures/test techniques, rock fractures, Concrete construction, Fracture, Mortar, Rocks, Sustainable development, Underground structures, Field conditions, Filtration erosions, Innovative procedure/test technique, Laboratory conditions, Test techniques, Water ingress
National Category
Geotechnical Engineering
Identifiers
urn:nbn:se:ri:diva-61211 (URN)10.1002/geot.202200023 (DOI)2-s2.0-85139241886 (Scopus ID)
Available from: 2022-12-05 Created: 2022-12-05 Last updated: 2023-10-09Bibliographically approved
Javadi, H., Urchueguía, J. F., Badenes, B., Mateo, M. Á., Nejad Ghafar, A., Arun Chaudhari, O., . . . Lemus, L. G. (2022). Laboratory and numerical study on innovative grouting materials applicable to borehole heat exchangers (BHE) and borehole thermal energy storage (BTES) systems. Renewable energy, 194, 788-804
Open this publication in new window or tab >>Laboratory and numerical study on innovative grouting materials applicable to borehole heat exchangers (BHE) and borehole thermal energy storage (BTES) systems
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2022 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 194, p. 788-804Article in journal (Refereed) Published
Abstract [en]

In this study, a laboratory-scale prototype of a borehole field has been designed and built to assess various innovative grouting products in a fully controlled environment. Three novel grout formulations are developed and evaluated: enhanced grout, a mixture of enhanced grout and microencapsulated phase change material, and a mixture of enhanced grout and shape stabilized phase change material. The objective is to evaluate the enhancement in their thermal properties (i.e., thermal conductivity and thermal energy storage capacity) compared to those using a commercial reference grout. Besides, three-dimensional numerical modeling is performed to provide a better understanding of the heat transfer and phase transition inside and outside the grout columns and to study the capability of the developed grouts to be used in a borehole heat exchanger or as borehole thermal energy storage system. To the best of the authors' knowledge, there have been just a few numerical studies on using phase change materials inside borehole heat exchangers to assess thermal energy storage applications. The experimental and numerical results showed much higher efficiency of the grout developed with a high thermal conductivity than the reference grout in terms of heat transfer in both the grout column and the surrounding sand. Furthermore, the results indicated the noticeable influence of the microencapsulated phase change material's presence in the grout formulation in terms of heat absorption/storage during the phase transition (from solid to liquid). However, it is concluded that reengineering shape stabilized phase change material should be conducted to make it more appropriate for thermal energy storage applications.

National Category
Infrastructure Engineering
Identifiers
urn:nbn:se:ri:diva-59880 (URN)10.1016/j.renene.2022.05.152 (DOI)2-s2.0-85131566138 (Scopus ID)
Note

This article is part of a project that has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 727583.

Funding for open access charge: AYUDAS A INVESTIGADORES PREDOCTORALES PARA LA PUBLICACIÓN DE ARTÍCULOS DE INVESTIGACIÓN EN ABIERTO (PAID-12-21) by Universitat Politècnica de València.

Available from: 2022-08-08 Created: 2022-08-08 Last updated: 2023-06-02Bibliographically approved
Arun Chaudhari, O., Ghafar, A., Zirgulis, G., Mousavi, M., Fontana, P., Pousette, S. & Ellison, T. (2021). A Practical Construction Technique to Enhance the Performance of Rock Bolts in Tunnels. In: Proc of ICTC 2021: . Paper presented at ICTC 2021: 15. International Conference on Tunnel Construction Date and location – December 16-17, 2021 in Barcelona, Spain Conducted online due to pandemic)..
Open this publication in new window or tab >>A Practical Construction Technique to Enhance the Performance of Rock Bolts in Tunnels
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2021 (English)In: Proc of ICTC 2021, 2021Conference paper, Published paper (Refereed)
Abstract [en]

In Swedish tunnel construction, a critical issue that has been repeatedly acknowledged is corrosion and, consequently, failure of the rock bolts in rock support systems. The defective installation of rock bolts results in the formation of cavities in the cement mortar that is regularly used to fill the area under the dome plates. These voids allow for water-ingress to the rock bolt assembly, which results in corrosion of rock bolt components and eventually failure. In addition, the current installation technique consists of several manual steps with intense labor works that are usually done in uncomfortable and exhausting conditions, e.g., under the roof of the tunnels. Such intense tasks also lead to a considerable waste of materials and execution errors. Moreover, adequate quality control of the execution is hardly possible with the current technique. To overcome these issues, a nonshrinking/ expansive cement-based mortar filled in the paper packaging has been developed in this study which properly fills the area under the dome plates without or with the least remaining cavities, ultimately that diminishes the potential of corrosion. This article summarizes the development process and the experimental evaluation of this technique for the installation of rock bolts. In the development process, the cementitious mortar was first developed using specific cement and shrinkage reducing/expansive additives. The mechanical and flow properties of the mortar were then evaluated using compressive strength, density, and slump flow measurement methods. In addition, isothermal calorimetry and shrinkage/expansion measurements were used to elucidate the hydration and durability attributes of the mortar. After obtaining the desired properties in both fresh and hardened conditions, the developed dry mortar was filled in specific permeable paper packaging and then submerged in water bath for specific intervals before the installation. The tests were enhanced progressively by optimizing different parameters such as shape and size of the packaging, characteristics of the paper used, immersion time in water and even some minor characteristics of the mortar. Finally, the developed prototype was tested in a lab-scale rock bolt assembly with various angles to analyze the efficiency of the method in real life scenario. The results showed that the new technique improves the performance of the rock bolts by reducing the material wastage, improving environmental performance, facilitating and accelerating the labor works, and finally enhancing the durability of the whole system. Accordingly, this approach provides an efficient alternative for the traditional way of tunnel bolt installation with considerable advantages for the Swedish tunneling industry.

Keywords
Corrosion, durability, mortar, rock bolt
National Category
Infrastructure Engineering
Identifiers
urn:nbn:se:ri:diva-57528 (URN)
Conference
ICTC 2021: 15. International Conference on Tunnel Construction Date and location – December 16-17, 2021 in Barcelona, Spain Conducted online due to pandemic).
Available from: 2022-01-05 Created: 2022-01-05 Last updated: 2023-06-02Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3572-8873

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