Experience with light dynamic penetration in a landslide locality

Because of vital prevention and redevelopment measures in problem localities affected by slope instability, geotechnical investigations must be carried out. One of the applicable methods is Light Dynamic Penetration (LDP). Although it was designed for easy field investigations in planning line structures to identify parameters, such load bearing capacity, and compactness, its use proves to be much wider. Using LDP it is possible to detect the interfaces between the discrete layers, potential slip surfaces, or groundwater level. However, it is important to note that the results of LDP are always related to one point only and to investigate a whole area, a complementary survey is needed. In the paper we report research where we used a geophysical method of Electrical Resistivity Tomography (ERT) to validate the results rendered by Light Dynamic Penetration in a redeveloped post-mining locality characteristic of landslides. The results of both measurement methods were unified for better interpretation and clarification to find out whether LDP is suitable to investigate a landslide locality. It shows that LDP provides relevant information on the massif structure in a given locality, but as opposed to other geophysical methods LDP informs only about one point only. The authors thus recommend carrying out surveys in landslide areas combining LDP and ERT as complementary measurements of groundwater level in the openings made using LDP. Mutually combining these two methods, it is possible to obtain a number of valuable information on landslide conditions (depth and course of shear plane, groundwater level, structure of layers, etc.) and physical-mechanical properties of soils

Testing of Sealing Elements for FIB Apparatus Designed to Liquidate Open Eruption by Drilling Tools

Petroleum and natural gas still have their place among the most important resources in many industrial areas. Their global consumption influences an increasing demand on the quality of drilling works and the efficiency of extraction. Nonetheless, even in this field of human activity, we can encounter exceptional events and accidents. One of the most serious kinds of accidents during exploration is the so called open eruption of extracted medium. The specific case of this accident is an open eruption caused by drilling tools when a working crew is not capable of securing drilling workplace. In order to solve this emergency situation, Main Mining Rescue Station Hodonin (HBZS Hodonin),in cooperation with researchers from Faculty of Mining and Geology at VSB -Technical University of Ostrava, designed and developed specialised apparatus DPRP (Drill Pipe Rescue Press), working designation FIB-1. This apparatus enables the liquidation of eruption by pressing the drilling pipe. The residual crack, which remains following the pressing, must be eliminated by sealing materials. This paper reviews the testing of sealing elements (materials), designed by our team, in residual crack of circle shape with help of hydraulic press MTS 816 Rock Test System

Effects of cyclic loading on the rheological properties of sandstones

This paper presents some results of the laboratory tests on the time-dependent behaviour of three types of sandstone. Research into the rheological properties of rocks is mostly done under static (quasistatic) loading. In nature, however, rocks are also often subjected to cyclic (vibration) loading as a result of vibrations from traffic or the propagation of seismic waves due to, for example, earthquakes, rock bursts, blasting operations and such like. On this account, the research presented is focused on the study of rheological rock properties during vibration (cyclic) loading. The tests of the rheological properties of a cyclic load were conducted both in creep regime and in relaxation regime, at various levels of average load or strain and for various parameters of vibration (frequency, amplitude). The measured values of different parameter settings were compared and evaluated so that it was possible to set the dependence of cyclical rock loading in the rheological regime. For the purpose of the comparison of rock behavior during vibration and static loading, other tests were also carried out. The results of the research show that, in the course of cyclical loading, the rock rheological properties depend, to a significant extent, on the parameters of this loading, especially the amplitude and frequency.Web of Science3221420

Determination of the Uniaxial Compressive Strength of Rocks from the Strength Index

The uniaxial compressive strength (UCS) is classified as one of the basic mechanical properties of rocks, which is widely used in mining and construction practice. For example, it allows geomechanics to classify individual rocks and soils into groups with the same or similar mechanical properties. An example is the (RMR) Rock Mass Rating, Barton’s Q system. [1,2]. As a rule, only an indicative determination of the uniaxial compressive strength is sufficient for this classification.The uniaxial compressive strength is determined in the laboratory on regular test pieces. The preparation of these test bodies is often a time-consuming and costly process, and in some cases, the recommended shape cannot be prepared for a small amount of rock sample or, in the case of highly fractured and friable rock. For this reason, alternative methods for determining compressive strength are being sought. These methods are supposed to be faster and cheaper and to provide results directly in situ. The paper presents information obtained from the indirect determination of the uniaxial compressive strength according to the strength index measured with a field press on various rock types from the Czech Republic

Možnosti hodnocení stability skalních stěn v lomových provozech

Prezenční542 - Katedra hornického inženýrství a bezpečnostiNeuveden

Indikační plyny samovznícení uhelné hmoty

Import 29/03/2011Prezenční542 - Institut hornického inženýrství a bezpečnostiNeuveden

Binární ukazatele samovznícení uhlí v ostravsko-karvinském revíru

V létech 1986-2001 probíhala v OKR výzkumná aktivita pojmenovaná "Pasportizace slojí náchylných k samovznícení". Celkem bylo zpracováno 62 uhelných vzorků. Součásti obsahů výzkumných zpráv, katalogů, byly plynové obrazy plynných produktů tepelné oxidace obsahující plyny CO, CO2, H2, úbytek O2 a nasycené a nenasycené plynné uhlovodíky C2-C4. pro vyhodnocení plynových obrazů byly vytvořeny dva výpočetní programy. V obsahu článku jsou uvedeny vybrané binární plynové ukazatele, které mohou být uplatněny v OKR pro odhad teploty ohniska samovznícení uhlí.In the years 1986-2001, the research acitivity called "Cataloguing of seams from the viewpoint of their tendency towards spontaneous combustion" had run in the Ostrava-Karviná District (OKR) in the Czech part of Upper Silesian Basin. Totally 62 coal samples were documented. The gas images of gaseous products of thermal oxidation of coal samples containing the gases CO, CO2, decrease of O2, H2 and saturated and non-saturated gaseous hydrocarbons C2-C4 created an integral part of catalogues. For the purposes of these gas imagines evaluation two computer databases and two computing programs for evaluation of basic materials were created. In content of the article the selected binary ratios of gases are emphasized which can be applied in the OKR practice for indication of temperature of spontaneous combustion focus

The assessment of stress in an exploited rock mass based on the disturbance of the rigid overlying strata

Gravitational rules are used as the basis for the prognosis of vertical stress distribution in exploited rock masses. A decrease in stress in a worked-out area (decrease between the initial stress and the stress acting on the floor of the outmined seam) results in an increase in stress in the surrounding unworked area. The size of load in the floor of the worked-out area is determined by the degree of disturbance in the overlying strata rocks. An overall additional load in the surrounding rocks of the unworked area is determined based on the difference between the initial geostatic stress and the load in the floor of the worked-out area. The additional load, which is determined from the force of relieving the stress in the worked-out area divided by the periphery of the worked-out area, decreases per unit of length of the periphery of the worked-out area. Furthermore, the behaviour of stress in the direction of the worked-out area is calculated mathematically. In this way, the stress in the grid of points on the level of seams being mined can be calculated, and isolines of acting stress can be determined. As an example, we show calculations for a specific situation in a mine before rigid overlying strata failure and after the failure. After the rigid overlying strata failure, the additional stress decreased by approximately 40%.Web of Science50827

Possibilities of exploitation of graphite deposit in the Czech republic

This article deals with mining technical proposals for the renewal of graphite raw material mining in the immediate vicinity of the town of Český Krumlov, where there are three sub-locations called Městský Vrch, Lazec-Křenov and Bíca. These sites are significant in terms of the quantity of natural graphite reserves, a raw material listed as a critical raw material by the EU. This list is regularly updated to reflect changing economic importance and supply challenges based on industrial availability. The article describes possible alternatives for the resumption of graphite mining in the Český Krumlov deposit (Městský Vrch and Lazec – Křenov localities). It describes the initial situation at the Český Krumlov deposit after the end of mining and the alternatives for the design of opening and mining operations. The authors conclude by comparing the advantages and disadvantages of the proposed alternatives.Web of Science28120019

An investigation of the factors associated with interpretation of mine atmosphere for spontaneous combustion in coal mines

The risk of spontaneous combustion of coal is highly serious especially in gaseous underground coal mines. In many cases such a spontaneous combustion is a source of initiation of methane-explosive mixture with tragic consequences. Early indication of spontaneous combustion and determination of its seat temperature is in a given environment a key part of safety of underground coal mines. A commonly used method for the detection of spontaneous combustion is an interpretation of coal oxidation gas products whose historical roots go back to the first halve of the 20th century as Graham's ratio. In the second half of this century a wide research on application of desorbed higher hydrocarbons C1–C4 and hydrogen for the given purpose took place. Until now, the interpretations in question encounter significant inaccuracies. The paper describes the research on factors affecting the accuracy of the determination of coal spontaneous combustion temperature on conditions of underground coal mines. The research was focused on the accuracy of interpretation of mine gases in connection with the use of laboratory verified gas characteristics of thermal oxidation of coal. Three chromatograph laboratories had been involved to test thermal oxidation of coal to determine a deviation of spontaneous combustion gases. The variability among the laboratories and used techniques were insignificant. Besides the laboratory methods, it may not reflect processes in coal mines and one of the results was that coal itself had been a source of substantial variability of desorption of spontaneous combustion gases. The spontaneous combustion data still requires human interpretation. Simple criteria for providing warning by a computer do not exist just yet