Fredrik Johansson

Fredrik Johansson
KTH Royal Institute of Technology | KTH · Department of Civil and Architectural Engineering

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59
Publications
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529
Citations

Publications

Publications (59)
Article
Full-text available
Significant uncertainties remain regarding the field assessment of the peak shear strength of rock joints. These uncertainties mainly originate from the lack of a verified methodology that would permit prediction of rock joints’ peak shear strength accounting for their surface area, while using information available from smaller samples. This paper...
Article
Full-text available
Grout curtains are commonly constructed under dams to reduce the seepage through the rock foundation. In the design of grout curtains, empirical methods have mainly been used since the introduction of dam foundation grouting. Although empirical methods have been used with success in several projects, they have their limitations, such as poor contro...
Article
The storage of hydrogen gas in underground lined rock caverns (LRCs) enables the implementation of the first fossil-free steelmaking process to meet the large demand for crude steel. Predicting the response of rock mass is important to ensure that gas leakage due to rupture of the steel lining does not occur. Analytical and numerical models can be...
Article
Fine-grained infilling materials in rock fractures cannot be penetrated by cement-based grout, while high water velocities in the unfilled parts of the fracture can impose erosion of the infilling materials. Understanding the erosion process of the infilling materials is, therefore, essential for the design of grout curtains. In this paper, the inc...
Article
Full-text available
This paper presents an investigation of the influence of large-scale asperities on the shear strength of four physical models of a pillar (also known as buttress web) from Kalhovd dam in Norway. The objective was to observe the structural behaviour of the pillar under design and ultimate loading scenarios and to compare results of the tests with th...
Article
Full-text available
The mechanical behaviour of natural, unfilled rock joints is influenced by the interaction between surface roughness and matedness of the contact surfaces. In the field, natural rock joints normally exhibit a mismatch between the contact surfaces, mainly due to different geological processes such as weathering or deformations. Various attempts have...
Conference Paper
Full-text available
To reduce the water leakage and the uplift pore pressure in the rock foundation, grout curtains are often constructed under dams. However, the design of grout curtains has long been based on empirical knowledge. When designing the grout curtain, focus was mainly given on closing the curtain and limiting the leakage, without considering the thicknes...
Conference Paper
Efforts to decrease CO2 emissions in the Swedish steelmaking process involve the use of industrial quantities of hydrogen gas supplied from large-scale Lined Rock Cavern (LRC) storages in order to eliminate the use of fossil fuels. This storage must be placed at sufficient depth so that the overburden is able to resist the uplifting gas pressure fr...
Article
Full-text available
The location and geometry of large-scale asperity present at the foundation of concrete gravity dams and buttress dams affect the shear resistance of the concrete-rock interface. However, the parameters describing the frictional resistance of the interface usually do not account for these asperities. This could result in an underestimate of the pea...
Article
Full-text available
A common approach to verify a shotcrete layer’s ability to secure blocks that can exist between rockbolts in a tunnel is to use analytical calculations. For this situation, an attractive approach to account for variability in the shotcrete parameters is to use reliability-based methods. Variability can then be accounted for by assigning suitable pr...
Article
Full-text available
In comparison with other types of construction, the development of rock engineering design codes has been slow. Codes must, however, be developed with relevant discipline-specific characteristics in mind. This paper, therefore, presents a generic design framework for rock engineering. The framework is based on the presumption that rock engineering...
Article
This paper presents the development and installation of a prototype ice load panel and measurements of ice load from February 2016 to February 2018 at the Rätan hydropower dam in Sweden. The design of the 1 × 3 m² panel enables direct measurement of ice pressure on the concrete surface is based on previous experience from similar measurements with...
Article
Landslides as major geo-hazards in Sweden adversely impact on nearby environments and socio-economics. In this paper, a landslide susceptibility map using a proposed subdivision approach for a large area in southwest Sweden has been produced. The map has been generated by means of an artificial neural network (ANN) model developed using fourteen ca...
Conference Paper
Efforts to substitute the use of fossil fuels in industry by hydrogen gas requires the storage of large volumes of gas with a reliable pressure vessel design. The Hydrogen Breakthrough Ironmaking Technology (HYBRIT) initiative aims to make the whole steel making process in Sweden fossil-free with the storage of industrial scale quantities of hydrog...
Article
Full-text available
A common support measure for underground excavations in jointed rock masses to support loose blocks is to apply a thin shotcrete layer to the periphery of the excavation and systematically install rockbolts into the surrounding rock mass. In this support system, large blocks are carried by the rockbolts and small blocks are carried by the thin shot...
Article
Full-text available
The European design code for geotechnical engineering, EN-1997 Eurocode 7, is currently under revision. As design of underground openings in rock fundamentally differs from design of most other types of structures, the revised Eurocode 7 must be carefully formulated to be applicable to underground openings. This paper presents the authors’ view of...
Conference Paper
In this paper, a reliability based framework for the assessment of sliding stability for concrete dams was presented. The framework consists of several parts based on the Probabilistic model code for concrete dams developed by Westberg-Wilde and Johansson and includes guidelines on how reliability based sliding stability assessment should be perfor...
Book
Full-text available
The objective of HYBRIT RP1 is to explore and assess pathways to fossil-free energy-mining-iron-steel value chains and thereby provide a basis for industrial development activities and the necessary future transformative change in this field. A large-scale storage capacity for hydrogen gas is an important component of the proposed HYBRIT concept. U...
Conference Paper
Full-text available
A comprehensive understanding of the shear strength and the mechanical behavior of rock joints is to some extent still missing today. Several attempts have been made to develop empirical and analytical shear strength criteria that explain this mechanism. One of the most important parameters governing the shear strength of rock fractures is the surf...
Article
Limitations with the current design using partial factors in Eurocode 7 have been identified. Uncertainties in the material properties are incorporated in both the cautious estimate of the characteristic value and the partial factor. Furthermore, the partial factor is fixed, which limits the opportunities to update the design when additional inform...
Article
Full-text available
According to Eurocode 7, two accepted approaches for managing uncertainty in tunnel design are reliability-based methods and the observational method. Reliability-based methods account for uncertainty by acknowledging the random variation of the input parameters; the observational method does this by verifying the expected behavior from an initial...
Technical Report
Fulltext: urn:nbn:se:kth:diva-221063 In this report, the influence of degradation on the strength of rock bolts has been studied. A literature study has been performed in order to determine the degradation rate and to present observations and conclusions from available assessments of rock bolts. All cases found in the literature have shown that th...
Conference Paper
In order to sufficiently seal an underground facility in fractured rock, it is essential to obtain adequate grout spread into the surrounding fractures. The grout spread itself depends on parameters, the most significant of which are the filtration tendency and rheological properties. These properties can be affected by the applied pressure. High-f...
Article
Limitations with the current design using partial factors in Eurocode 7 have been identified. Uncertainties in the material properties are incorporated in both the cautious estimate of the characteristic value and the partial factor. Furthermore, the partial factor is fixed, which limits the opportunities to update the design when additional inform...
Conference Paper
The Swedish national guidelines for design of the main structural support system in road and railway rock tunnels have been adjusted to cohere with Eurocode 7. In the design guidelines, the limit states that the designer should consider are specified. The main method to account for uncertainties in the Swedish guidelines is similar to the method pr...
Conference Paper
Full-text available
In this paper, detailed numerical and analytical calculations are presented with the aim to study the effect of rock bolts and the influence of degradation on the dam safety. In addition, results from inspections and pull-out tests are presented from a case study with rock bolts that has been installed for 50 years. All tested bolts have with margi...
Article
Full-text available
The observational method in geotechnical engineering is an acceptable verification method for limit states in Eurocode 7, but the method is rarely used despite its potential savings. Some reasons may be its unclear safety definition and the lack of guidelines on how to establish whether the observational method is more favourable than conventional...
Article
Full-text available
Although there are many proposed relations for different rock types to predict the uniaxial compressive strength (UCS) as a function of P-wave velocity (V P) and point load index (Is), only a few of them are focused on marlstones. However, these studies have limitations in applicability since they are mainly based on local studies. In this paper, a...
Conference Paper
Full-text available
The updated safety-factor requirements for stability of concrete gravity dams in several European countries have resulted in making many existing dams theoretically unsafe. Furthermore, the contribution to stability from bonding, cohesion and rock-bolts are often neglected or underestimated in the design methods usually used. The reason behind is,...
Poster
Full-text available
This poster presents a short history of grouting in micro-fractures < 70 µm, the mechanisms, and problems in the past and present and our expectation in future. It also shows the industrial application of the proposed method. Two experimental setups used in this study are presented together with some illustrative results and conclusions on potentia...
Article
Full-text available
As concrete dams age, the need for remedial grouting to reduce the seepage and uplift pressure in the rock foundations under them increases. Based on a case study of a Swedish dam with very low calculated safety against sliding, this paper discusses the application of the observational method (as defined in Eurocode 7) to manage safety aspects duri...
Article
For concrete dams, cohesive strength often constitutes a significant share of the overall shear strength of partially bonded concrete-rock interfaces. However, cohesive strength is also associated with great uncertainties that may have a significant impact on the assessed stability of the analyzed structure. In this paper, the merits of including c...
Article
Full-text available
The shear strength of the concrete–rock interface has a substantial influence on the sliding stability of concrete gravity dams founded on rock. While several studies have been done on concrete–rock contacts, there remains uncertainty regarding the peak shear strength of partially bonded interfaces. There exists, in particular, an uncertainty regar...
Article
It is widely recognized that the mechanical parameters for unfilled and rough rock joints, such as the peak shear strength, can vary with scale. However, due to contradictory results concerning the extent and nature of the scale effect reported in the literature, it is still a debated subject. A conceptual model developed by Johansson and Stille 20...
Conference Paper
Full-text available
At shallow depth, in situ stress can affect significantly the behavior of the rock mass around excavations, but stress measurements are usually subjected to high levels of uncertainty. This is the case at the Odenplan railway station in Stockholm where unexpected large values of displacements were recorded during the excavation. A sensitivity analy...
Conference Paper
According to Eurocode 7, the observational method is an accepted design method, where a preliminary design may be updated as the construction progresses. However, Eurocode 7 does not give any advice on how to relate the observations to the acceptable level of safety of the structure. In this paper, we outline a methodology for how to use deformatio...
Article
Full-text available
The limit equilibrium method (LEM) is widely used for sliding stability evaluation of concrete gravity dams. Failure is then commonly assumed to occur along the entire sliding surface simultaneously. However, the brittle behaviour of bonded concrete-rock contacts, in combination with the varying stress over the interface, implies that the failure o...
Conference Paper
Krångfors is a concrete dam located in northern Sweden that was constructed in three stages from 1928 to 1973. This expansion in different stages resulted in a complicated structural design. Extensive cracks have been noticed in parts of the structure. Two main hypotheses for the cause of these cracks were initially established; 1) alkali-silica re...
Conference Paper
Full-text available
Dams in countries with cold climate are subjected to ice loads during the winter, and these may have significant influence on the dam stability. The design value of the horizontal ice load varies between 50-200 kN/m from the South to the North of Sweden, according to the Swedish guideline for dam safety (RIDAS 2011). However, the size of the ice lo...
Conference Paper
Full-text available
In order to determine the in-situ shear strength of rock joints, large scale testing is required. However, this is both expensive and difficult to execute. One possible method to overcome this may be to use photogrammetry to capture large joint surface roughness in-situ and downscale it to replica samples, which could be sheared in laboratory. In t...
Article
The correlation between Standard and Cone Penetration Tests (SPT and CPT) as two of the most used in-situ geotechnical tests is of practical interest in engineering designs. In this paper, new SPT-CPT correlations for southwest of Sweden are proposed and developed using an artificial neural networks (ANNs) approach. The influences of soil type, dep...
Technical Report
Full-text available
Title: Failure of Concrete Dams In consequence classification of concrete dams, or in dam breach simulations for emergency preparedness studies, the assumptions on the width of the failure and the rate of development of the breach is essential for the results. The knowledge on failure modes for concrete dams is good but the knowledge on the width a...
Article
Several criteria have been proposed over the years in order to predict the peak shear strength of rock joints. The most widely used criterion is the JRC–JCS criterion by Barton. It says that changes in the peak shear strength originate from surface roughness, joint wall compressive strength and normal stress. A limitation with this criterion is tha...
Article
Full-text available
In probabilistic stability analyses of concrete dams founded on rock, the uplift pressure is often a parameter of major importance. In previous literature, it has been suggested that assessing uplift with pore pressure measurements, instead of using empirical assumptions, could improve the calculated dam safety. This paper presents a coherent metho...
Article
Structural reliability analysis is not widely used for the design and assessment of concrete dams. In this paper, the system reliability of a spillway structure consisting of two monoliths is calculated. Limit state functions are defined from the failure modes sliding in the concrete rock contact, sliding in the rock mass, and adjusted overturning....

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Projects

Projects (6)
Project
A new design concept of grout curtain under dams is expected to be developed based on the existing theories on rock grouting.