Wyniki wyszukiwania - Biblioteka Nauki

1

The influence of the geometrical construction of the powered roof support on the loss of a longwall working stability based on the practical experience

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Rajwa S.

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tom Vol. 65, no. 3

511--529

EN

This article focuses on the difficulties in ensuring longwall stability resulting from the wrong geometric form of the structure of powered support sections. The authors proved, based on the in-situ measurements and numerical calculations, that proper cooperation of the support with the rock mass requires correct determination of the support point for the hydraulic legs along the length of the canopy (ratio), as well as the inclination of the shield support of the section of the powered roof support. The lack of these two fundamental elements may lead to roof drops that directly impact the production results and safety of the people working underground. Another matter arising from the incorrect geometric form of the construction are the values of forces created in the node connecting the canopy with the caving shield, which can make a major contribution to limit the practical range of the operational height of the powered roof support (due to interaction of powered support with rockmass) in terms of the operating range offered by the manufacturer of the powered support. The operating of the powered roof support in some height ranges may hinder, or even in certain cases prevent, the operator of powered support, moving the shields and placing them with the proper geometry (ensuring parallelism between the canopy and the floor bases of the section).

2

Zagrożenie zawałami w zakładach górniczych KGHM Polska Miedź SA w 2019 roku (Komunikat)

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Juszczyński D. , Wowczuk G.

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tom nr 10

10--12

PL

Jednym z zagrożeń występujących podczas wykonywania robót górniczych jest możliwość powstania zawału stropu wyrobiska. W artykule, na tle statystyki zawałów w polskich kopalniach rud miedzi w latach 2005-2020, przedstawiono charakterystykę zawałów w zakładach górniczych LGOM w 2019 r. wraz z omówieniem ich przyczyn.

EN

The hazard of roof fali affects underground mines all over the world, especially where the room and pillar mining system and roof bolting are applied. The paper presents at first statistics of roof faIIs in Polish copper mines for 2005-2020 period. There are two, in average, roof falls in yearly (the fali is defined as a rock mass drop reaching up to the extent of bolts length or above). Analysis of three cases of roof failures in Polish copper mines that occurred in 2019 shows that there is no just one main cause of the failure. However, generally, the geological structure and the presence of joints and cracks in the roof were the causes of rock failures in the 2019.

3

Czynniki wpływające na powstawanie obwałów skał w ścianach prowadzonych z zawałem skał stropowych

100%

Prusek S.

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2014

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tom T. 70, nr 3

71--78

PL

Występujące w ścianach utrudnienia w utrzymaniu stropu, takie jak opady czy też obwały, negatywnie wpływają na wyniki ekonomiczne kopalń oraz pogarszają bezpieczeństwo pracy załogi górniczej. W artykule przedstawiono wybrane wyniki dotychczas prowadzonych badań w zakresie opadów i obwałów, występujących w ścianach prowadzonych z zawałem stropu w kopalniach polskich i zagranicznych. Podano wyniki badań ankietowych przeprowadzonych w polskich kopalniach węgla kamiennego, a dotyczących określenia przyczyn powstawania pogorszonych warunków utrzymania stropu w ścianach zawałowych. Badania ankietowe pozwoliły na określenie głównych czynników geologicznych, górniczych oraz technicznych, decydujących o stateczności skał stropowych w ścianach.

EN

Roof instabilities occurring in the longwalls, such as roof falls, have a negative effect on the economic performance of mines and deteriorate significantly the safety of miners. This paper presents the selected results of studies on roof falls, occurring in the longwalls with natural roof caving in Polish and foreign mines. The results of a survey on the causes of worse roof conditions occurring in the longwalls, conducted in Polish coal mines were presented. The survey allowed to determine the main geological, mining and technical factors which influence the stability of the roof in longwalls.

4

The Assessment of Longwall Working Stability Based on the Mohr-Coulomb Stress Criterion – Numerical Analysis

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Janoszek T. , Janoszek T.

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5

Numeryczna analiza wpływu własności skał stropowych na możliwości ograniczenia ich opadu w wyrobisku ścianowym

84%

Tomiczek K.

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2017

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tom Vol. 6, iss. 3

274--284

PL

Jednym z podstawowych czynników wpływających na bezpieczeństwo i ciągłość procesu eksploatacji jest zapewnienie niezakłóconego wybierania pokładu poprzez utrzymanie stateczności skał występujących w stropie oraz w czole ściany przed stropnicami obudowy zmechanizowanej oraz zapobieganie niekontrolowanemu opadowi skał stropowych lub bloków węgla do przodka. Na podstawie przykładów eksploatacji trzech ścian S-2, S-3 i S4 w pokładzie 403/1, prowadzonych z zawałem warstw stropowych, przeprowadzono uproszczone analizy numeryczne używając programu różnic skończonych FLAC2D (Itasca C.G.). Badano wpływ własności skał stropowych i węgla na zasięg stref uplastycznienia oraz zniszczenia skał przed- i nad czołem ściany. Przeprowadzone analizy stanowiły negatywną weryfikacją prowadzonych dotychczas działań powodujących osłabienie górotworu i wskazywały na konieczność podjęcia takich, które zmierzałyby do jego wzmocnienia.

EN

One of the primary factors affecting the safety and permanence of the process of longwall mining excavation is to ensure the stability of rocks occurring in the roof and in the working face in front of the roof bar of the powered roof support and the prevention of uncontrolled roof fall to the free working face. Based on the examples of the operation of three longwalls with roof caving: S-2, S-3 and S4 on 403/1 coal bed were conducted simplified numerical analysis using the finite difference program FLAC2D (Itasca CG). The influence of properties of roof rock and coal to propagation of areas plasticity and damage of rocks in front of and above the working face. The analyzes conducted negative verification of activities carried out so far causing the weakening of the rock and pointed need of such tending to strengthen it.

6

The assessment of longwall working stability based on the Mohr-Coulomb stress criterion – numerical analysis

84%

Janoszek T.

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tom Vol. 65, no. 3

493--509

EN

The use of computer techniques at the design stage of industrial facilities is essential in modern times. The ability to shorten the time required to develop a project and assess the safety of the use of assumptions, often enables the reduction of the costs incurred in the future. The possibility to skip expensive prototype tests by using 3D prototyping is why it is currently the prevailing model in the design of industrial facilities, including in the mining industry. In the case of a longwall working, its stability requires the maintenance of the geometric continuity of floor rocks in cooperation with a powered roof support.The paper investigates the problem of longwall working stability under the influence of roof properties, coal properties, shield loading and the roof-floor interaction. The longwall working stability is represented by an index, factor of safety (FOS), and is correlated with a previously proposed roof capacity index ‘g‘. The topic of the paper does address an issue of potential interest. The assessment of the stability of the roof in longwalls was based on the numerical analysis of the factor of safety (FOS), using the Mohr-Coulomb stress criterion. The Mohr-Coulomb stress criterion enables the prediction of the occurrence of failures when the connection of the maximum tensile principal stress σ1 and the minimum compressive principal stress σ3 exceed relevant stress limits. The criterion is used for materials which indicates distinct tensile and compressive characteristics. The numerical method presented in the paper can be utilized in evaluating the mining natural hazards through predicting the parameters, which determine the roof maintenance in the longwall working.One of the purposes of the numerical analysis was to draw attention to the possibilities that are currently created by specialized software as an important element accompanying the modern design process, which forms part of intelligent underground mining 4.0.