Ákos Török

Ákos Török
Budapest University of Technology and Economics · Department of Engineering Geology and Geotechnics

PhD, DSc

About

204
Publications
98,241
Reads
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2,605
Citations
Introduction
Historic sites, monuments, air pollution, stone and mortar testing, slope stability, radioactive waste disposal site selection
Additional affiliations
January 2015 - February 2016
Budapest University of Technology and Economics
Position
  • Professor (Full)
September 1986 - March 2015
Budapest University of Technology and Economics
Position
  • Professor (Full)
Description
  • Engineering Geology Unit with expertise in: Accredited Material Testing Laboratory (Stone, Mortar, Brick), Diagnostics of Monuments, Radioactive Waste Disposal, Tunnelling, Slope Stability, Mineral Resources Evaluation, Sedimentary Geology, Diagenesis

Publications

Publications (204)
Article
Full-text available
The freezing technique has been employed for a long time to strengthen the mechanical properties of intact rock and rock mass; however, it has not received as much attention as it deserves. This paper thoroughly reviews the effect of freezing on the essential mechanical properties, including uniaxial compressive strength, tensile strength, and Youn...
Article
Loessial soil is moisture-sensitive soil susceptible to settle when fully saturated. In this study, efforts were made to investigate the effect of oil pollutants on mechanical behavior of soil. The loess soil was contaminated by 2,4,6,8 and 10% dry weight of lamp oil and gasoline. Atterberg limits, direct shear, unconfined compressive strength (UCS...
Article
Full-text available
The mechanical properties of frozen rocks vary significantly from the properties of the same lithology under ambient temperature. The goal of this paper is to investigate these changes in the physical and mechanical properties of rocks due to saturation and freezing. Besides, the attention was paid on discovering new correlations between the mechan...
Article
Full-text available
An accurate determination of Hoek–Brown constant m i is of great significance in the estimation of the failure criteria of brittle rock materials. So far, different approaches such as rigidity index method (R-index), uniaxial compressive strength-based method, and tensile strength-based method, and the combination of these two methods (combination...
Article
Water saturation is considered one of the major factors influencing stones deterioration. The effect of moisture on the deterioration process of stone was investigated with the help of ultrasonic wave velocities. P and S waves velocities were calculated for twelve different lithotypes including limestone (porous limestone, laminated and less-lamina...
Article
Full-text available
The time-dependent stability of tunnels is an important and challenging topic, mainly when the tunnel is excavated in incompetent and weak rocks. The creep property of rock is one of the crucial mechanical properties of weak rock and the main factor affecting the long-term stability of rock masses. Also, water as an important environmental factor i...
Conference Paper
Full-text available
Soft rocks have an important role in the geological structure of Dalmatia (Croatia) and Budapest area (Hungary). In general, soft rocks are transitional material between the hard rock and soft soil with compressive strength below 25 MPa. A lower limit of soft rock strength is a subject of many discussions in geotechnics. Most of the soft rock mater...
Article
Full-text available
The evaluation of shear stress versus shear displacement curves is in the main focus of geotechnical engineering. Such curves, depending on the rock assessed, consist of a quasi-linear section, followed by a "kick" representing the peak shear strength, and a residual part, mostly parallel to the abscissa. The aim of the present study is to facilita...
Article
Syracuse and the other cities of the Hyblaean area (in south-eastern Sicily) are characterized by a close relationship between building stone and geological context, since the wide use of local calcarenites characterized and defined their urban planning and architecture. In this paper, we discuss the results of a research aimed at investigating fou...
Article
Full-text available
Cylindrical specimens obtained from the monzogranite host rock of the National Radioactive Waste Repository of Hungary were tested at room temperature and 250 °C, 500 °C, and 750 °C of heat treatment. Reflectance spectra (color), bulk density, Duroskop surface hardness, and ultrasound-wave velocity values were measures before and after thermal stre...
Article
Low- and intermediate-level radioactive waste is stored in the National Radioactive Waste Repository in Bátaapáti in Hungary. The repository is located in the Carboniferous Mórágy Granite Formation. This paper focuses on heat-related changes of physical properties such as bulk density, P-wave velocity, P-wave modulus, and Duroskop surface hardness...
Article
Full-text available
The durability of consolidated highly porous limestones was tested after salt and freeze–thaw cycles. Three porous limestone lithotypes that were commonly used in construction in the Central-European region during previous centuries were selected for the tests. Specimens of Miocene limestone were consolidated with four different types of ethyl sili...
Article
Full-text available
A comprehensive understanding of geological, structural geological, hydrogeological and geotechnical features of the host rock are essential for the design and performance evaluation of surface and underground excavations. The Hungarian National Radioactive Waste Repository (NRWR) at Bátaapáti is constructed in a fractured granitic formation, and T...
Article
Full-text available
Testing long-term properties of aggregates requires time consuming laboratory tests. Alternatively, mathematical models can also be used to describe the abrasion process of aggregates. The paper uses another approach it links long-term abrasion to rock mechanical properties to facilitate a quick assessment of long term behavior of aggregates. It ex...
Article
Precast concrete segments are mainly loaded by thrust jacks during the installation stage. It is then essential to limit the cracks and damages of the segments during this phase to be sure of their structural integrity and sustainability. Using fibers, the cracks can be better controlled and stabilized in the concrete. It will allow to lead to smal...
Article
Full-text available
Determining linear elastic stiffness parameters is a crucial aspect of ground characterization that enables subsequent numerical analyses using finite element, discrete element, and other procedures. Before estimating global settings for a rock mass relative to a proposed excavation such as a rock slope, tunnel or cavern, it is essential to underst...
Article
Full-text available
Four different porous limestone lithotypes were collected from the cellar system of Budapest (Hungary). All lithologies have high porosities ranging from 16 to 30%. The laboratory analyses focused on the mechanical properties testing to assess the strength changes due to water saturation. The density, ultrasonic sound wave propagation, uniaxial com...
Article
Full-text available
Aggregates are necessary materials for the construction industry. Owing to their favourable properties, andesites are frequently used rock materials; hence, the investigation of their mechanical and aggregate properties has great significance. This paper introduces the analyses of 13 Hungarian andesite lithotypes. The samples were collected from si...
Preprint
Full-text available
The program for the final disposal of low and intermediate level radioactive waste has been established by the Paks Nuclear Power Plant, Hungary. The Central Nuclear Financial Fund and the Public Limited Company for Radioactive Waste Management (PURAM) has been established to coordinate organizations and activities for all tasks in connection with...
Article
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Construction materials of a partly ruined Medieval church of Central Hungary were studied in details to assess its conditions and to obtain information on the phases of construction. At first, digital images were taken to create a 3D model of the remaining walls. The material properties were measured in situ using non-destructive test methods. Stre...
Article
Full-text available
Volcanic tuffs have a historical tradition of usage in Northern Hungary as dimension stones for monumental construction, Ottoman architecture, common dwellings, etc., admirable at its best in the medieval castles of Eger and Sirok. This research explores tuff deterioration in the castle walls, dealing with the mineralogical composition, microstruct...
Article
Full-text available
A 3D surface model of an active limestone quarry and a vegetation-covered plateau was created using unmanned aerial vehicle (UAV) technique in combination with terrestrial laser scanning (TLS). The aim of the research was to identify major fault zones that dissect the inaccessible quarry faces and to prepare a model that shows the location of these...
Article
Full-text available
Abstract This paper demonstrates the application of in situ diagnostic tools to document stone heritage sites prior to conservation interventions using a Medieval ruin of Central Europe (Székesfehérvár, Hungary). The applied methods included lithological mapping and characterisation and mapping of decay forms as well as in situ measurements of phys...
Article
Volcanic tuffs are notoriously very heterogeneous materials exhibiting a recurrent lithological diversity, which, in turn, can be associated with changing petrophysical and mechanical properties. This variability was investigated on a small scale in different Miocene acid tuffs extracted in the same quarry region, within just a few km radius from t...
Article
Full-text available
The durability of aggregates against salt weathering is calculated after five cycles of immersion in a magnesium sulfate solution followed by drying according to the relevant European standard (EN 1367–2: 2010). The aim of the study is to investigate the long-term durability of aggregates by increasing the number of cycles of the salt crystallizati...
Article
Full-text available
Freeze-thaw cycles can cause considerable damage to porous materials and thus have an adverse effect on the durability of mortars and porous stone. To assess the behavior and frost resistance of two types of porous limestone, three commercially available repair mortars and four mixtures of laboratory-prepared repair mortars were subjected to freeze...
Conference Paper
Full-text available
The cellars are usually the result of previous quarrying activities. The area of these cavities nowadays located under urban areas and usually makes difficult the urban developments. There are some areas in Budapest where cellars are found below future construction sites therefore detailed investigation of these cellar systems are required. The inv...
Conference Paper
Full-text available
The paper compares the engineering geological parameters of Croatian flysch deposits and Hungarian marls with respect to slope stability. Eocene flysch deposits are widespread sediments in Central Dalmatia. They form gentle to steep slopes in the countryside and in urban areas, with risks of slope instability. Especially weathered and long-time exp...
Conference Paper
Full-text available
Nearly 30 m high rock slope construction was necessary in soft rock condition during the construction of main road No. 21 in Hungary. Using rock mechanical laboratory test results, two different empirical rock classes (Slope Mass Rating-SMR and Q-slope) were applied to calculate the stability of the rock slope. For these calculations, the angles be...
Chapter
Full-text available
The mechanical properties of frozen rocks are very different from the properties of the same lithologies under ambient temperature. The goal of this paper is to describe the changes in the physical parameters of rocks caused by freezing. In addition, estimations are given on how these parameters are influenced by the intrinsic properties of rocks....
Article
Full-text available
8 different natural stone types were exposed to exhaust gas under laboratory conditions to assess urban stone damage. 3 cm in diameter cylindrical test specimens were made from travertine, non-porous limestone, limestone, rhyolite tuff, sandstone, andesite, granite and marble. The samples were exposed for 1, 2, 4 and 8 hours to exhaust gas that was...
Chapter
Anisian Muschelkalk ramp cycles are well documented from the northwestern Tethys shelf and its northern Peri-Tethys Basin by detailed studies in Germany, the Netherlands, Poland, and Hungary. High-resolution correlation based on cyclostratigraphy has been attempted in recent years, but is still hampered by precise age control. The recent approach o...
Article
Full-text available
This study presents five different lithotypes of limestone containing stylolites and commonly used as dimension stones in Egypt, Hungary and Israel. All the studied limestones are generally hard, dense, with high degree of cementation and have high strength and low porosity. Stylolites are small tooth-like irregular surfaces most often developed on t...
Article
Mineral carbonation has been proposed as a safe method for carbon capture and storage (CCS). Mafic lithologies are among the most promising rocks for mineral carbonation due to their high content in Ca, Fe and Mg-bearing silicate minerals, which react with CO2 to form stable carbonate phases. Here, we discuss the potential of using waste material f...
Conference Paper
Full-text available
The shear strength of rocks along discontinuities is one of the key parameters for the determination of rock slope stability, the stability of rocks during underground space development and tunneling. Its value is influenced by numerous factors including surface roughness, which is one of the most widely investigated discontinuity property. The pre...
Article
Full-text available
The effect of particulate matter - as a component of an internal combustion engine's exhaust gas - on 8 different types of construction materials have been studied under laboratory conditions. Our aim was double. On the one hand it was to investigate the degree of discolouration, whether there is a difference between the 8 types of rock in the same...
Article
Full-text available
Twenty-seven samples of black weathering crust and host carbonates were studied from seven European countries (Germany, Hungary, Belgium, Czech Republic, France, Italy and Poland) representing 11 different sites. The samples were collected for sites for which long-term air pollution records are available. The mineralogical analyses (XRD, polarizing...
Article
Full-text available
Steep, hardly accessible cliffs of rhyolite tuff in NE Hungary are prone to rockfalls, endangering visitors of a castle. Remote sensing techniques were employed to obtain data on terrain morphology and to provide slope geometry for assessing the stability of these rock walls. A RPAS (Remotely Piloted Aircraft System) was used to collect images whic...
Article
Full-text available
Shear strength along rock discontinuities by means of direct shear strength tests were performed on granitic and clayey rocks. Both rock types represent potential host rocks of radioactive waste. The paper focuses on the effect of one parameter in particular influencing the shear strength: the angle enclosed by the plane of the sample surface and t...
Article
Full-text available
This paper focuses on the effect of high temperature on the mechanical properties of a porous limestone that is widely used as dimension stone in Hungary. The changes in physical properties of 3 types of porous limestone were analyzed at 22 °C, 300 °C and 600 °C, respectively. The limestone specimens were also subjected to freeze-thaw cycles to ass...
Article
Full-text available
The Micro-Deval test method is used for testing of aggregate durability. The present paper focuses on two Hungarian andesites obtained from the quarries of Recsk (Mátra Mountains, Hungary) and of Nógrádkövesd (Cserhát Mountains, Hungary). The aim of this study is to find a simple test method based on the original Micro-Deval test method to assess t...
Article
Full-text available
Aggregate properties and strength parameters of four andesites from two operating Hungarian quarries of Nógrádkövesd (one lithotype) and Gyöngyössolymos (three lithotypes) are presented in this paper. Air-dry, water-saturated and freeze–thaw subjected specimens were tested on core-drilled cylindrical specimens, and the aggregate properties were als...
Article
Full-text available
Four ready-mix commercial available repair mortars—that are used for porous limestone repair—were studied under different laboratory conditions. To have better compatibility with porous limestone, not only pure mortars but also mortars with 50 wt% of limestone aggregate was tested. The reason why limestone aggregate was added to mortar was to modif...
Article
Full-text available
Low strength rhyolite tuff forms steep cliffs in NE Hungary. A multi-dimensional approach including field analysis and laboratory tests was conducted to understand the mechanical properties of the tuff and to measure discontinuity surfaces. With the help of RPAS (Remotely Piloted Aircraft System) and TLS (Terrestrial Laser Scanning), a digital terr...
Article
Full-text available
The shear strength of rocks along discontinuities has the highest influence on rock slope stability; therefore, its accurate determination is crucial. This paper presents a potential solution for the 3D surface detection of the rock discontinuity surfaces by using photogrammetric methods (ShapeMetriX3D), from which one of the most important shear s...
Article
Full-text available
Adhesion strength between porous limestone and 8 repair mortars (4 commercial and 4 laboratory mixture) was tested. The composition of repair mortars was modified by adding aggregates, resulting in 1:3 and 1:5 binder/aggregate ratio. The limestone surface was either pre-treated (wetted) or dry. The pull-off strength was measured by using standard t...
Article
Full-text available
A cikk a Magyar Tudományos Akadémia Széchenyi-téri székháza ünnepélyes átadásának másfélszáz éves évfordulója alkalmából bemutatja a várostörténeti szempontból is kiemelkedő jelentőségű középület építése során alkalmazott kőanyagokat. Történeti szemlélettel ismerteti az építő- és díszítőkövek felhasználásának körülményeit, típusait, valamint levélt...
Conference Paper
Full-text available
Steep, and hardly accessible jointed rhyolite tuff cliff faces surround a Castle in NE-Hungary, at village of Sirok. The assessment of cliff stability required the recording of cliff geometry. Traditional surveying was not possible therefore cliff faces were 3D modelled by GNSS supported terrestrial laser scanner and UAV. The onsite engineering geo...
Conference Paper
Full-text available
Elevated temperature causes changes in mechanical properties of rock, due to thermal effect and mineralogical transformations, which show great varieties for different lithologies. The present paper provides information on seven different sandstones. The studied predominantly quartz sandstones show different petrology from fine-grained to coarse-gr...
Article
Full-text available
The stability of reservoir slopes is critical to the safe operation of reservoirs and is intensely affected by cyclic wetting and drying (W-D) caused by water level fluctuation. A new cyclic W-D test was performed on remoulding specimens to explore the influence of cyclic W-D on the microstructure of slip zone soils. Firstly, the unsaturated compac...