Variations in rock support capacity due to local variations in bond strength and shotcrete thickness

Sjölander, Andreas; Ansell, Anders; Malm, Richard

doi:10.1016/j.engfailanal.2021.105612

Cited by 4 publications

(4 citation statements)

References 19 publications

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“…How these affect the structural capacity is not well studied, and a numerical study was therefore conducted. The complete results from this study are presented by Sjölander et al [21] and summarized below.…”

Section: Local Variations In Thickness and Bond Strengthmentioning

confidence: 93%

“…This modelling approach was used by Sjödin [22] and enables the user to control the variations by specifying the number of cosine waves, 𝑀𝑀 and 𝑁𝑁, the amplitude of each wave, 𝑎𝑎(𝑚𝑚, 𝑛𝑛) as well as the phase angle between each wave defined by 𝜙𝜙(𝑚𝑚, 𝑛𝑛). For a complete description see [22] and for a more thorough description of its implementation to study variations in bond strength see [21]. With this approach, the variations in bond strength will vary smoothly over the surface and clusters with high and low bond strength values will exist.…”

Section: Local Variations In Shotcrete Bond Strengthmentioning

confidence: 99%

“…As for the case with varying bond strength, there is a strong linear correlation between the mean shotcrete thickness and the failure load. As discussed in [21], one possible explanation for the strong correlation between failure load and the mean value of shotcrete bond and thickness is the combination of a stiff interface and a narrow area over which the bond stress is transferred. Thus, local weak sections may initiate the failure but will not control the failure progression.…”

Section: Local Variations In Shotcrete Thicknessmentioning

confidence: 99%

See 2 more Smart Citations

Failure Mechanisms of Fibre Reinforced Shotcrete: Numerical Simulations Considering Local Variations in Thickness and Bond Strength

Sjölander

Ansell

2022

Nordic Concrete Research

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Fibre-reinforced shotcrete is the most common support method for hard rock tunnels in the Nordic countries. The design of shotcrete is often based on empirical methods or simplified analytical equations, which neglect variations in mechanical properties and shotcrete thickness. Data collected from the field shows that significant variations in shotcrete thickness and bond strength should be expected during tunnel construction. However, how this affects the structural behaviour and capacity of the shotcrete lining is unknown. Moreover, the design philosophy for shotcrete assumes that the primary failure modes of shotcrete, i.e. bond and flexural failure, can be treated separately. This was derived based on observations of experiments in a laboratory environment. Therefore, the focus of a finalized doctoral project was to develop a numerical framework to simulate the structural behaviour of fibre-reinforced shotcrete in interaction with hard rock and rock bolts. The effect of variations in shotcrete thickness and bond strength was studied through numerical simulations to increase the understanding of its effect on the failure load of the lining. The results indicate that the most important parameter is the mean value of the shotcrete thickness and bond strength around a narrow perimeter of the block.’

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Section: Local Variations In Thickness and Bond Strengthmentioning

confidence: 93%

Section: Local Variations In Shotcrete Bond Strengthmentioning

confidence: 99%

Section: Local Variations In Shotcrete Thicknessmentioning

confidence: 99%

See 1 more Smart Citation

Failure Mechanisms of Fibre Reinforced Shotcrete: Numerical Simulations Considering Local Variations in Thickness and Bond Strength

Sjölander

Ansell

2022

Nordic Concrete Research

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“…The horizontal line indicates the requirements for f TPL re and E RDP , respectively. As reported in [54], in situ measurements of stresses and failures of shotcrete linings are rare, and the load acting in the shotcrete is complex to analyze. To determine a suitable residual capacity for the shotcrete lining and to point out which of the presented design methodologies that is most suitable is therefore difficult.…”

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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A new method for measuring the adhesion strength of rock-concrete specimens based on the calibration interface of the modified flat-joint model

Lan

Zhang

et al. 2022

Engineering Failure Analysis

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Variations in rock support capacity due to local variations in bond strength and shotcrete thickness

Cited by 4 publications

References 19 publications

Failure Mechanisms of Fibre Reinforced Shotcrete: Numerical Simulations Considering Local Variations in Thickness and Bond Strength

Failure Mechanisms of Fibre Reinforced Shotcrete: Numerical Simulations Considering Local Variations in Thickness and Bond Strength

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

A new method for measuring the adhesion strength of rock-concrete specimens based on the calibration interface of the modified flat-joint model

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