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

100%

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

Optimisation of selected parameters of the shield support base dedicated for the condition of a weak floor

63%

Rajwa S. , Bock S.

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tom Vol. 67, no. 3

509--529

EN

In longwall coal exploitation, problems with the proper functioning of the powered shield support often occur. In many cases, it results from the insufficient load-bearing capacity of the ground (floor) and the inability to achieve the set or yield pressure of the shield support. The improper functioning of the shield support may also result from its construction and the lack of optimisation to work effectively on a weak mine floor. This paper presents an attempt to optimise the operating conditions of the base of two-legged shield support based on the field observations and results of the PFC3D numerical calculation. In the framework of the numerical calculations, the impact of the width of the base and the location of the hydraulic legs on the working conditions of shield support on a weak floor were analysed.

3

Geomechanical assessments of longwall working stability – a case study

51%

Nguyen P. M. V. , Rajwa S. , Płonka M. , Stachura W.

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tom Vol. 67, no. 2

333--354

EN

The stability of longwall mining is one of the most important and the most difficult aspects of underground coal mining. The loss of longwall stability can threaten lives, disrupt the continuity of the mining operations, and it requires significant materials and labour costs associated with replacing the damages. In fact, longwall mining stability is affected by many factors combined. Each case of longwall mining has its own unique and complex geological and mining conditions. Therefore, any case study of longwall stability requires an individual analysis. In Poland, longwall mining has been applied in underground coal mining for years. The stability of the longwall working is often examined using an empirical method. A regular longwall mining panel (F3) operation was designed and conducted at the Borynia-Zofiówka-Jastrzębie (BZJ) coal mine. During its advancement, roof failures were observed, causing a stoppage. This paper aims to identify and determine the mechanisms of these failures that occurred in the F3 longwall. A numerical model was performed using the finite difference method - code FLAC2D, representing the exact geological and mining conditions of the F3 longwall working. Major factors that influenced the stability of the F3 longwall were taken into account. Based on the obtained results from numerical analysis and the in-situ observations, the stability of the F3 longwall was discussed and evaluated. Consequently, recommended practical actions regarding roof control were put forward for continued operation in the F3 longwall panel.

4

Badania modelowe mechanizmu zawisania stropu wyrobiska ścianowego w warunkach eksploatacji złoża systemem ścianowym

51%

Janoszek T. , Rajwa S. , Walentek A.

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tom T. 75, nr 9

1--13

PL

W artykule zwrócono szczególną uwagę na zagadnienie związane z trudnością w utrzymaniu stateczności wyrobiska ścianowego w przypadku niekorzystnego zjawiska zawisania stropu wyrobiska ścianowego w warunkach prowadzonej eksploatacji systemem ścianowym na zawał. W tym celu przeprowadzono badania analityczne i numeryczne z zamiarem określenia parametrów, które determinują proces zawisania warstwy stropu wyrobiska ścianowego. Metodą analityczną badano wpływ parametrów fizyko- -mechanicznych oraz geometrycznych górotworu na proces zawisania stropu wyrobiska ścianowego nad zrobami interpretowany wartością jego ugięcia. Przedstawiono schemat obliczeniowy oraz warunki wytrzymałościowe procesu wydłużania belki (wspornika) w stropie wyrobiska. Natomiast za pośrednictwem obliczeń numerycznych badano wpływ wybranych parametrów modelu Coulomba-Mohra na wartości długości wspornika oraz obniżenia stropu dla określonych parametrów geometrycznych i mechanicznych obudowy zmechanizowanej. Otrzymane wyniki badań modelowych pozwoliły na określenie zależności opisujących wpływ wybranych parametrów mechanicznych skał i geometrycznych warstwy stropu wyrobiska ścianowego na proces jego powstawania i zawisania.

EN

The article focuses on the problem in maintaining the stability of a longwall working caused by the unfavourable phenomenon of the hanging roof in a longwall working. Model tests were carried out, intended to define the parameters that determine the process of roof hanging, based on the analytical and numerical methods. The analytical method was applied to study the influence of physic-mechanical and geometrical parameters of the rockmass on the process of roof hanging in the longwall working, interpreted the value of its deflection. The calculation scheme as well as the strength and stress conditions of the roof beam lengthening process in the longwall working are presented. Whereas, in the numerical calculations the influence of parameters of the Coulomb-Mohr’s model on the length and the deflection of the roof strata for given geometrical and mechanical parameters of the powered roof support, were investigated. The obtained results allowed to determine parameters describing influence of the selected mechanical and geometric parameters of the roof of the longwall working on the process of its hanging.

5

Rozwój konstrukcji stalowych odrzwi do rozcinek ścianowych

38%

Caban P. , Stoiński K. , Rotkegel M. , Rajwa S. , Gnatowski A. , Pacześniowski K.

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tom R. 58, nr 2

41--58

PL

Artykuł przedstawia rozwój konstrukcji obudów stalowych dla górnictwa, produkowanych przez Hutę Łabędy S.A. z przeznaczeniem do zabezpieczania wyrobisk korytarzowych, a szczególnie rozcinek ścianowych. Na przestrzeni ostatnich dekad obudowa rozcinek rozruchowych ewoluowała między innymi pod względem kształtu. Stosowane początkowo odrzwia prostokątne i typowe odrzwia ŁP z poszerzeniami zostały zastąpione przez odrzwia spłaszczone na bazie łuków ŁP (ŁPKO), a następnie przez specjalne odrzwia dostosowane kształtem do sekcji obudowy zmechanizowanej. Uzyskano w ten sposób obrys odrzwi pośredni, będący kompromisem pomiędzy prostokątnym (korzystnym z uwagi na zbrojenie i uruchomienie ściany), a łukowym (korzystnym z uwagi na wysokie parametry podpornościowe).

EN

The article presents the development of steel frame sets produced for mining purposes by Huta Łabędy S.A., intended for securing gallery workings, and longwall development drifts in particular. In recent decades, longwall development drift support has evolved in terms of characteristics such as its shape. The initially utilised rectangular frames and typical widened ŁP frames were replaced with flat frames based on ŁP arches (ŁPKO), and subsequently with special frame sets adapted to the shape of powered support units. The intermediate frame shape obtained in this way was a compromise between the rectangular (beneficial from the perspective of longwall equipment and development) and the arching design (beneficial due to the high load-bearing parameters).