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1

Rock pore structure as main reason of rock deterioration

Ondrášik M., Kopecký M.

Studia Geotechnica et Mechanica

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2014

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Vol. 36, nr 1

79--88

EN

Crashed or dimensional rocks have been used as natural construction material, decoration stone or as material for artistic sculptures. Especially old historical towns not only in Slovakia have had experiences with use of stones for construction purposes for centuries. The whole buildings were made from dimensional stone, like sandstone, limestone or rhyolite. Pavements were made especially from basalt, andesite, rhyolite or granite. Also the most common modern construction material – concrete includes large amounts of crashed rock, especially limestone, dolostone and andesite. However, rock as any other material if exposed to exogenous processes starts to deteriorate. Especially mechanical weathering can be very intensive if rock with unsuitable rock properties is used. For long it had been believed that repeated freezing and thawing in relation to high absorption is the main reason of the rock deterioration. In Slovakia for many years the high water absorption was set as exclusion criterion for use of rocks and stones in building industry. Only after 1989 the absorption was accepted as merely informational rock property and not exclusion. The reason of the change was not the understanding of the relationship between the porosity and rock deterioration, but more or less good experiences with some high porous rocks used in constructions exposed to severe weather conditions and proving a lack of relationship between rock freeze-thaw resistivity and water absorption. Results of the recent worldwide research suggest that understanding a resistivity of rocks against deterioration is hidden not in the absorption but in the structure of rock pores in relation to thermodynamic properties of pore water and tensile strength of rocks and rock minerals. Also this article presents some results of research on rock deterioration and pore structure performed on 88 rock samples. The results divide the rocks tested into two groups – group N in which the pore water does not freeze even when the temperature decreases to –20 ºC, and the second group F in which the pore water freezes. It has been found that the rocks from group N contain critical portion of adsorbed water in pores which prevents freezing of the pore water. The presence of adsorbed water enables thermodynamic processes related to osmosis which are dominantly responsible for deterioration of rocks from group N. A high correlation (R = 0.81) between content of adsorbed water and freeze-thaw loss was proved and can be used as durability estimator of rocks from group N. The rock deterioration of group F is caused not only by osmosis, but also by some other processes and influences, such as hydraulic pressure, permeability, grain size, rock and mineral tensile strength, degree of saturation, etc., and the deterioration cannot be predicted yet without the freeze-thaw test. Since the contents of absorbed water and ratio between adsorbed and bulk water (of which the absorbed water consists) is controlled by the porosity and pore structure, it can be concluded that the deterioration of some rocks is strongly related to rock pore structure.

2

Complex geodetic and photogrammetric monitoring of the Kraľovany rock slide

Fraštia M., Marčiš M., Kopecký M., Liščák P., Žilka A.

Journal of Sustainable Mining

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2014

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Vol. 13, iss. 4

12--16

EN

Purpose The complex monitoring of rock slides with the size of 16 ha in order to predict the development of other slides and prevent possible human and material losses. Methods Precise geodetic point measurement, terrestrial laser and image scanning and aerial photogrammetry were used to obtain detailed knowledge about the geometry and behaviour of the rock slide. Except for terrestrial images, the images were taken using an SLR camera (set on a motor paraglide) and a compact camera (set on a remotely piloted system). The state and condition of the locality before the rock slide was taken from archive images taken by a digital large format camera. Results Vectors and velocities of the displacements of discrete points were determined with high precision; the changes in quarry wall surfaces were determined by laser and photogrammetry scanning. Finally, high resolution orthophotomosaics of the site were generated using aerial photogrammetry at each observation point. Practical implications The termination of mining and the design of the remediation works were determined according to the results of the measurements. Also, monitoring was carried out in order to observe any changes due to the implementation of a highway project based in the localisation. Originality/ value Complex geodetic and photogrammetric monitoring of rock slides offers detailed information about slide surfaces and has previously been used in Slovakia on a significant scale.

3

Horizontal drains as effective measure for landslide remediation

Kopecký M., Ondrášik M., Antolová D.

Studia Geotechnica et Mechanica

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2013

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Vol. 35, nr 1

129--142

EN

Decrease of groundwater table level or decrease of buoyancy effects of groundwater is one of the most important landslide remediation measures. In Slovakia as well as in the world the horizontal drainage boreholes are often used for the landslide remediation. The article describes 40 years’ experience with use of the horizontal drainage boreholes in Slovakia, particularly in terms of their effectiveness and long-term functionality.

4

Model for RTS noise in submicron MOSFETs

Šikula J., Sedláková V., Pavelka J., Navarová H., Chvátal M., Kopecký M.

Zeszyty Naukowe Wydziału ETI Politechniki Gdańskiej. Technologie Informacyjne

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2010

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T. 18

409-414

EN

The paper presents a model for RTS noise in submicron MOSFETs which can explain some of complex switching phenomena being measured in nanoscale devices. A modified two-step approach is proposed. The charge carrier quantum transitions represent a primary process X(t), which involves two or three quantum states. The measurable quantity is the current modulation, which has discrete states and is represented by a secondary process Y(t). From the dependence of the capture time constant c on the drain current we can calculate x-coordinate of the trap position.

PL

W pracy przedstawiono model szumu RTS w submikronowych tranzystorach MOSFET, który może wyjaśnić niektóre ze złożonych zjawisk przełączania obserwowanych w przyrządch o nanoskali. Zaproponowano zmodyfikowane podejście dwu etapowe. Kwantowe przejścia nośników ładunku reprezentują pierwotny proces X(t) o dwóch lub trzech stanach kwantowych. Wielkością mierzalną jest modulacja prądu o stanach dyskretnych, reprezentujaca proces wtórny Y(t). Na podstawie zależności stałej czasowej pułapkowania c od prądu drenu można wyznaczyć współrzędną x położenia pułapki.

5

A View on The Ways Design of Reliability Criteria in Structural Mechanics

Kopecký M.

Machine Dynamics Research

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2010

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Vol. 34, No. 3

124-132

EN

Contemporary intensive development of technology puts ever-increasing demands on the reliability of products. The increase in the reliability level is emphasised also in transport machines and equipment. This all requires a further improvement of the method of designing and strength checking of a construction. The methods described in this paper are the ways to reach the solution goals with the maximum use of computer technology. A practical example of loading system analysis in presented which demonstrates use the special instrument to measurement of distribution the force and torsion moment in card an-joint for control purposes and uses the special instrument to generally measurement of distribution random loading parameter. In some machinery and equipment, or their elements, the problem of strength reliability is due to the present-day regulations conditioned by a fatigue process and by knowledge of a fatigue curve. A considerable part of dynamically loaded components in mechanical engineering is loaded with time-variable strength. In the case of the means of machinery , competitiveness leads to weight reduction savings and extreme operational situations cause high overloading. It is probable that the most significant cause of this unfortunate situation is the fact that so far there has not been a single universal theoretically and experimentally proved fatigue theory which would consider all the factor that have an influence on the phenomena. Apart from this, there is not a generally accepted methodology of fatigue tests. A demand to guarantee strength reliability is more important predominantly in case when a failure-free operation of a constructional element can influence the safety of human lives or when an eventual failure can bring about considerable economic losses. The variability of fatigue mechanisms in the Wohler curve belongs among the questions so far not clearly specified. It has to be said, that insufficient information about the values of the fatigue curve can lead to errors sometimes higher than 100%. Also, because of economic and others reasons, it is impossible to carry out sufficient amount of fatigue tests on a finished product in order to get reliable information about the fatigue curve. It is further connected with a choice of a suitable commutation of a fatigue failure which can also lead to different results. Random operational loading creates a stochastic process of excitation forces. A successful reproduction of the response of this random loading depends on the technical facilities. With regard to a probability character of the fatigue curve, where its exponents p, q, have a character of a random quantity, a total service life is also a random quantity characterized by a probability density. The probability that a failure might occur before a required servicelife Lp ends is given by a hatched surface. The methods described in this paper are the ways to reach the solution goals by means of a characteristic curve of strength reliability and reduced fatigue curve with the maximum use of computer technology. The application of this methodology shortens knowledge of the time to failure of mobile machine components and contributes to the safety and economy of mechanical systems. The results of its application would be presented to mobile facility elements.

6

An analysis of the natural frequencies exerted on a bearing-type transferring fixed on the frame at the top

Vavro J., Kopecký M., Fandáková M.

Vibrations in Physical Systems

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2004

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Vol. 21

403--404

EN

The article is dealing with the natural frequencies analyse of the bearing-type transferring, which is attached to the frame from above. Transferring is a part of a production line, which is used in rubber industry and serves by the assembling of the truck tyres and tyres.

7

The Experimental Measurement of the Tire Impurities Circulation by the Dynamic Loading and Application of the Experimental Evaluation by the Method of the Active Factor Experiment

Vavro J., Kopecký M., Koštial P., Hajská H., Fandáková M.

Machine Dynamics Problems

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2004

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Vol. 28, No. 4

171-176

EN

The article is dealing with the measurement of the tire impurities circulation by the dynamic loading along with the disc. There are made measurements for the various tire velocities on the roadway by the constant inflation pressure in tire and by the tire constant external loading and time service longitudes. In the article is suggested the process of the measurement evaluation by the method of the active factor experiment.

8

The Cause of Dynamic Stress on Propagation of Cracks in Vulcanizates

Cúth V., Kopecký M., Švecová Z.

Machine Dynamics Problems

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2004

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Vol. 28, No. 3

77-82

EN

Vulcanized rubber composition - rubber - belongs to a very important constructional and technological materials. Especially its elastic properties, gave rise to its indispensableness in technical practice. Task of this paper is the understanding of influence of various strains special developed mixtures for personal tire on the increase of cracks during the working of the product, it means his cyclic stress. The experiments were performed at various on instrument programming deviced strains on tension equipment INSTRON 4302 according to methodics developed in VUG Matador a.s. Puchov, which support on effect detection of various factor which influenced the propagation of crack growth.

9

Rotating Machines Parts and their Vibration Control

Kopecký M., Cúth V., Vavro J.

Machine Dynamics Problems

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2004

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Vol. 28, No. 3

171-176

EN

The development of new aggregates of mobile machine aims at the reduction of production and operational costs and, at the same time, at the increase of transmitted power when a sufficient reliability is provided. Simultaneously, the real operational safety concerning maximum permissible stress is also rescued. This results in necessity of further more exact methods of design and strength control of aggregate elements. The use of vibration data from rotating machinery to determine machine health has a long history. A practical example of gearbox vibration frequency analysis is presented, which demonstrates the use of high-resolution frequency controls using zoom FFT for diagnostic purposes. It is intended to show how to get and interpret good results from controls, with particular reference to points, which arise in gearbox applications.

10

Lateral Forces Effect on Safety of Driving in Curve

Hajská H., Fandáková M., Kopecký M., Slabeycius J., Sága M.

Machine Dynamics Problems

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2004

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Vol. 28, No. 3

119-124

EN

In this contribution we presented measurements of lateral forces on a drum-testing machine. Measurements of lateral forces are introduced in tables and figures in dependence on radial load in different angles directional deviation.