In-Situ and Laboratory Investigation on Leaching and Effects of Early Curing of Shotcrete

Sjölander, Andreas; Ansell, Anders

doi:10.2478/ncr-2019-0014

Cited by 2 publications

(3 citation statements)

References 9 publications

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“…In an in situ investigation performed by Sjölander and Ansell [ 1 ], early leaching and the presence of cracks in a shotcrete rock support were investigated. No visible cracks were found, and most leached areas were dry, indicating that the leaching process had stopped.…”

Section: Damage and Degradation Of Concrete In Tunnelsmentioning

confidence: 99%

“…Inspections must be conducted to detect, observe, and measure damage such as cracks, water, and leaching, which can lead to decreased structural capacity. Cracks are a common initiation to the degradation of concrete and reinforcement, water often accelerates the deterioration, and leaching is common in structures with one-sided water pressure, such as tunnels [ 1 , 2 ]. Leaching is normally a slow process that takes many years to initiate, but the process can be accelerated if cracks are present or the quality of the shotcrete is lower.…”

Section: Introductionmentioning

confidence: 99%

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Towards Automated Inspections of Tunnels: A Review of Optical Inspections and Autonomous Assessment of Concrete Tunnel Linings

Sjölander

Belloni

Ansell

et al. 2023

Sensors

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In recent decades, many cities have become densely populated due to increased urbanization, and the transportation infrastructure system has been heavily used. The downtime of important parts of the infrastructure, such as tunnels and bridges, seriously affects the transportation system’s efficiency. For this reason, a safe and reliable infrastructure network is necessary for the economic growth and functionality of cities. At the same time, the infrastructure is ageing in many countries, and continuous inspection and maintenance are necessary. Nowadays, detailed inspections of large infrastructure are almost exclusively performed by inspectors on site, which is both time-consuming and subject to human errors. However, the recent technological advancements in computer vision, artificial intelligence (AI), and robotics have opened up the possibilities of automated inspections. Today, semiautomatic systems such as drones and other mobile mapping systems are available to collect data and reconstruct 3D digital models of infrastructure. This significantly decreases the downtime of the infrastructure, but both damage detection and assessments of the structural condition are still manually performed, with a high impact on the efficiency and accuracy of the procedure. Ongoing research has shown that deep-learning methods, especially convolutional neural networks (CNNs) combined with other image processing techniques, can automatically detect cracks on concrete surfaces and measure their metrics (e.g., length and width). However, these techniques are still under investigation. Additionally, to use these data for automatically assessing the structure, a clear link between the metrics of the cracks and the structural condition must be established. This paper presents a review of the damage of tunnel concrete lining that is detectable with optical instruments. Thereafter, state-of-the-art autonomous tunnel inspection methods are presented with a focus on innovative mobile mapping systems for optimizing data collection. Finally, the paper presents an in-depth review of how the risk associated with cracks is assessed today in concrete tunnel lining.

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Section: Damage and Degradation Of Concrete In Tunnelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Towards Automated Inspections of Tunnels: A Review of Optical Inspections and Autonomous Assessment of Concrete Tunnel Linings

Sjölander

Belloni

Ansell

et al. 2023

Sensors

Self Cite

View full text Add to dashboard Cite

show abstract

“…Hence, a shotcrete lining with a low residual capacity could be used. On the other hand, load-independent stresses, caused by, e.g., drying shrinkage and thermal expansion, could lead to severe cracking already in the construction phase as shown by, e.g., Ansell [55] and Sjölander and Ansell [56]. Hence, adding more fibres to increase the ductility and, possibly, to reduce the crack widths could be preferable.…”

Section: Structural Performancementioning

confidence: 99%

On the Design of Permanent Rock Support Using Fibre-Reinforced Shotcrete

Sjölander

Ansell

Nordström

2023

Fibers

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Fibre-reinforced shotcrete (sprayed concrete) is one of the major components in the support system for tunnels in hard rock. Several empirical design methodologies have been developed over the years due to the complexity and many uncertainties involved in rock support design. Therefore, this paper aims to highlight how the choice of design methodology and fibre type impacts the structural capacity of the lining and the emission of greenhouse gases (GHG). The paper starts with a review of different design methods. Then, an experimental campaign is presented in which the structural performance of shotcrete reinforced with various dosages of fibres made of steel, synthetic and basalt was compared. A case study is presented in which the permanent rock support is designed based on the presented design methods. Here, only the structural requirements were considered, and suitable dosages of fibres were selected based on the experimental results. The emission of GHG was calculated for all design options based on environmental product declarations for each fibre type. The result in this paper indicates that synthetic fibres have the greatest potential to lower the emissions of GHG in the design phase. Moreover, the choice of design method has a significant impact on the required dosage of fibres.

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In-Situ and Laboratory Investigation on Leaching and Effects of Early Curing of Shotcrete

Cited by 2 publications

References 9 publications

Towards Automated Inspections of Tunnels: A Review of Optical Inspections and Autonomous Assessment of Concrete Tunnel Linings

Towards Automated Inspections of Tunnels: A Review of Optical Inspections and Autonomous Assessment of Concrete Tunnel Linings

On the Design of Permanent Rock Support Using Fibre-Reinforced Shotcrete

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