Ákos Török

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

Collapsible soils are susceptible to high and relatively sudden volume change after wetting under a specific load. They tend to have a high initial void index (more than 40%), a low saturation degree (less than 60%), a high silt content (greater than 30%), and quick softening after reaching humidity (loss of bonding). Due to the settlement of the u...

Rocks deformed at low confining pressure are brittle, which means that after peak stress, the strength declines to a residual value established by sliding friction. The stress drop is the variation between peak and residual values. But no tension reduction takes place at high confining pressure. A proposed definition of the brittle-ductile transiti...

In order to understand how the in-situ primary stress state has evolved with subsidence and uplift in a granitic rock mass for anticipated of a radioactive waste repository in Hungary, the authors investigated the applicability of seismic tomography as an interpretive tool. Very high P wave velocity (V p) values were obtained during the tomographic...

Stone deterioration is a non-linear process that is difficult to observe in a short period. The current study documents surface changes related to material loss using terrestrial laser scanner (TLS) and explains the differences in weathering of lithotypes and different wall orientations of various weathering forms. Ruins of a medieval church constr...

Soft rocks in various forms of marly materials have an important role in the geological structure of Dalmatia (Croatia) and Budapest region (Hungary). These materials can cause serious problems in design and construction, due to their complex behavior under atmospheric conditions. For the purpose of better understanding soft rocks behavior and thei...

The present study evaluates the structural and environmental performance of recycled fibers as a low‐cost and eco‐friendly reinforcement of segmental tunnel lining. In this research, the defect effects in the support area are investigated using three types of scaled panel samples. In addition to the fiber‐only reinforced concrete, the performance o...

There are historic subsurface dimension stones in the capital of Hungary (Budapest) that were excavated in porous limestone. The stability of these subsurface openings is important, since most of them are located in urban areas, where existing buildings or new structures are planned to be built. The paper presents a detailed study considering the g...

Recognized as one of the most destructive geological disasters, a myriad of landslides has revived and developed in the Three Gorges Reservoir area under the combined action of various detrimental factors, becoming a nightmare for the residents over vicinity. Therefore, the pertinently regional landslide susceptibility mapping (LSM) is of great sig...

After the economic boom in Iraq-Kurdistan the infrastructural reorganization began, based on the design of the highway and road network. The construction of the high number of tunnels is required because of the relief of the region thus the tracing of the roads can be better. Our Hungarian team was responsible for the verification of the Iranian-de...

Defining the practical and proper rock failure criteria plays the most significant role in analysis and design in rock mechanics and rock engineering. Up to now, several failure criterions have been proposed for brittle rocks. Among them, Hoek-Brown failure criterion has received much attention and applied among the others for brittle rocks. The go...

Slope stability analysis has received substantial attention in the scope of rock mechanics and rock engineering for many years. Various methods are available for analysing the stability of the vertical slope. The objective of this paper is to extend the proposed theoretical equation regarding tensile strength (t), Poisson's ratio () and bulk dens...

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...

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...

The present paper provides a case study and an overview of the stability of high banks bordering the eastern basin of the largest central European lake, Lake Balaton, in Hungary. External factors such as rain, lake-water level, or pore water pressure are considered in the stability analysis. The slope stability was assessed using two software with...

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...

Frequent soil landslide events are recorded in the Three Gorges Reservoir area, China, making it necessary to investigate the failure mode of such riverside landslides. Geotechnical centrifugal test is considered to be the most realistic laboratory model, which can reconstruct the required geo-stress. In this study, the Liangshuijing landslide in t...

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...

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...

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...

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...

Landslides are often triggered by various mechanisms such as precipitation, increase in the groundwater table, surface load, etc. and are classified according to the geometry and intensity of the motion. This paper provides an inventory considering all these factors by interpreting landslide records and available maps of the lakeside banks of the l...

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...

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...

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...

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...

This study focuses on the mechanical parameters of Miocene limestones from Hungary. Four different lithotypes of porous limestone from two localities were analysed in laboratory conditions. These lithologies have been widely used for centuries as construction material in Central Europe. One type of the Badenian Leithakalk limestone, which is a bioc...

Salt weathering is one of the crucial causes of building stone decay. For assessing the durability of stones against salt weathering, a standardised test procedure (EN 12370:2020 Determination of resistance to salt crystallisation) is used: the mass loss of the stone is measured during sodium sulphate crystallisation cycles. Porous, Miocene limesto...

Medium-and low-level radioactive waste is stored in the subsurface galleries of a granitic formation in Southern Hungary. The main lithology is monzogranite. The present study focuses on the thermal behavior and characteristics of intact rocks and thermally exposed specimens. Cylindrical specimens were heated to 250°C, and 500°C in an electric oven...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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....

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...

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...

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...

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...

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...

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...

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...

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...