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Small-scale experiments for contour-boreholes blast
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.ORCID iD: 0000-0002-6858-2057
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.ORCID iD: 0000-0001-8564-3694
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.ORCID iD: 0000-0002-5872-5173
2024 (English)In: ISRM European Rock Mechanics Symposium (EUROCK 2024): New challenges in rock mechanics and rock engineering / [ed] Tomás R., Cano M., Riquelme A., Pastor J.L., Benavente D., Ordóñez S., Taylor & Francis, 2024, p. 601-606Conference paper, Published paper (Refereed)
Abstract [en]

Blasting is widely used in tunneling when mechanical excavation methods cannot be applied due to rock conditions or cost constraints. The blast design of the contour holes defines the damage to the remaining rock, which might change the rock support requirements. This study investigates the crack behavior in sequential boreholes through small-scale experiments on rock-like specimens. Cylindrical samples, prepared with speckles for Digital Image Correlation (DIC), varied in decoupling ratio, and the detonation cord was detonated simultaneously in the blast holes. The data was collected with an ultra-high speed camera (UHSC) for DIC. The results indicated the development of the cracks between the boreholes and their behavior towards the boundary of the samples. The results showed that in this experimental configuration, there is no significant difference between the different decoupling ratios. This study shows the importance of an optimum blast design to minimize the damage to the remaining rock.

Place, publisher, year, edition, pages
Taylor & Francis, 2024. p. 601-606
Keywords [en]
Crack propagation, Digital Image Correlation (DIC), Contour blasting, Tunneling, Decoupling ratio
National Category
Other Civil Engineering
Research subject
Mining and Rock Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-104910DOI: 10.1201/9781003429234-88ISI: 001310272000088Scopus ID: 2-s2.0-85200358253OAI: oai:DiVA.org:ltu-104910DiVA, id: diva2:1847275
Conference
ISRM European Rock Mechanics Symposium (EUROCK 2024), Alicante, Spain, July 15-19, 2024
Projects
BeFo (Rock Engineering Research Foundation, Sweden) project number 427, “Experimental and Numerical modeling of blast-induced damage around rock tunnel using LS-DYNA”
Note

ISBN for host publication: 978-103255144-9; 

Available from: 2024-03-27 Created: 2024-03-27 Last updated: 2025-01-17Bibliographically approved
In thesis
1. Small-scale Experiments for Blast-induced Damage: Exploring crack propagation through Digital Image Correlation
Open this publication in new window or tab >>Small-scale Experiments for Blast-induced Damage: Exploring crack propagation through Digital Image Correlation
2024 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Blasting plays a crucial role in several engineering applications, from mining and tunneling to demolition projects. One of the remaining challenges of this process is that it can significantly affect the integrity of the rock mass by inducing damage in the form of cracks. Broadening the understanding of the behavior of the blast-induced cracks is essential for predicting the damage. One way of investigating this issue is through small-scale blasting experiments focused on crack propagation behavior.

Controlled blasting experiments were conducted on rock-like cylindrical samples charged with Pentaerythritol tetranitrate (PETN) cords. Different blast designs were tested and a method for integrating a Digital Image Correlation (DIC) technique in the analysis was developed. The DIC system was composed of an Ultra High-Speed Camera (UHSC), a light system, and a data acquisition system. The setup was tested in a laboratory and underwent different calibrations before implementing it in the mine, where using explosives during the tests is allowed. The UHSC captured the blasting process regarding crack propagation. To analyze the development of the cracks, DIC technique was employed and results in terms of displacement versus time were measured from the sample surface.

The described experiments integrate a novel analysis approach to the results from the DIC technique and propose a way of interpreting the outcomes regarding crack development in terms of velocity. While developing the methodology, the pre-processing of the data (UHSC images) was shown to enhance the DIC analysis and affect the further post-processing of the results. The presented methodology proposes a human-independent procedure of analysis that can help to differentiate the displacement of the crack along its time. Nevertheless, a visual analysis of the results was performed to complement the results and try to broaden the understanding of the crack development process.

The DIC results indicated a nonconstant crack propagation velocity while the development patterns were interpreted to match previous literature. The experimental studies confirmed the radial propagation behavior surrounding the blasthole in the single borehole test, while the two borehole configurations show to influence the crack propagation direction and interconnection.

This work describes small-scale experiments that provide meaningful insights in crack propagation and how the different blast design parameters can affect their development. The findings of this study could be useful as an input of a predictive tool to assess blast-induced crack initiation and development.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2024
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Keywords
Small-scale experiments, Blast-induced cracks, Digital Image Correlation, Crack propagation behavior
National Category
Other Civil Engineering
Research subject
Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-104912 (URN)978-91-8048-515-9 (ISBN)978-91-8048-516-6 (ISBN)
Presentation
2024-05-28, C305, Luleå Tekniska Universitet, Luleå, 10:00 (English)
Opponent
Supervisors
Projects
BeFo (Rock Engineering Research Foundation, Sweden) project number 427, “Experimental and Numerical modeling of blast-induced damage around rock tunnel using LS-DYNA”
Available from: 2024-03-27 Created: 2024-03-27 Last updated: 2024-05-07Bibliographically approved

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R. San Miguel, CarlotaPetropoulos, NikolaosYi, Changping

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