Browsing by Subject "longwall mining"

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Access status: Open Access ,
An attempt to determine the cause of the strong tremor responsible for a rockburst in a hard coal mine based on numerical modeling and spectral parameters
(Wydawnictwa AGH, 2024) Wojtecki, Łukasz; Krawiec, Krzysztof; Ćwiękała, Mateusz; Dzik, Grażyna
Seismic and rockburst hazards represent significant challenges during the longwall mining of coal seams. One analytical approach to assess the potential for rockburst hazards involves reconstructing the stress conditions within the rock mass. This article reports on the findings from three-dimensional (3D) numerical modeling aimed at examining the distribution of maximum shear stress within the rock mass amid the longwall mining operations of the 703/1 coal seam in a mine situated in the Upper Silesian Coal Basin, Poland which was disrupted by a rockburst incident. On the day of the rockburst, substantial concentrations of maximum shear stress were identified in a thick sandstone layer proximate to the boundary of the overlying 624 coal seam located significantly above the 703/1 coal seam. The calculated maximum shear stress demonstrated an increase of approximately 80% over the values observed in the absence of edge effects. Furthermore, also higher concentration of maximum shear stress was identified within the geologically weaker strata adjacent to the 703/1 coal seam. These observations facilitated the classification of the examined rockburst as a stress-stroke phenomenon. Additionally, the study determined the spectral parameters of the tremor, which possessed an energy of 9.8 × 10$^{7}$ J and triggered the analyzed rockburst. The ratio of the seismic energy of S and P-waves confirmed a shear mechanism in the focus. The scope of inelastic deformation within the focal zone was also quantified. Following the event, the rock mass that had been destressed due to the significant tremor and subsequent rockburst exhibited reduced seismic activity upon the resumption of longwall mining of the 703/1 coal seam.
Access status: Open Access ,
Analiza numeryczna migracji metanu z warstw spągowych do wyrobiska ścianowego
(2007) Kwaśniewski, Marek Andrzej; Lasek, Stanisław
A two-dimensional numerical model of a large (1000 × 200 m) part of the rock masses in the vicinity of coal seam 349 in longwall panel 802 in region B in the Murcki colliery was built using the distinct element code UDEC. Longwall mining of this seam with roof caving was simulated in the model over a length of 450 m. It was found that migration of methane from coal seams lying beneath the mined seam is possible under conditions where the floor strata deform to a great extent, undergo separation, fracture and break into blocks. It was revealed that the fractured zone in thin floor layers built of weak rocks develops more rapidly than the caving zone over the minedout area and reaches a depth of about 30 m below the seam. The floor strata undergo an intense heave towards the mined-out area. Even at the early stages of mining, the upward movement of the strata exceeded 1.5 m. Under the assumption that (i) methane-bearing strata occur 15.6 m below seam 349 and include seam 350 and the strata lying beneath, and (ii) the methane reservoir pressure is equal to 2 MPa, the direction, pressure, quantity and velocity of the methane flow through cracks developing in the floor strata under the area of seam 349 being mined were investigated.
Access status: Open Access ,
Innovative Mine Floor Grinding Machine
(Wydawnictwa AGH, 2024) Niezgoda, Franciszek; Zając, Janusz; Mitko, Kazimierz; Górecka, Izabela; Mojżysz, Stanisław
This article describes the process of development of the Hydroma floor grinding machine. It describes the current methods of solving exploitation problems related to uplifting of the floor in mining facilities and the issues of the need to maintain proper crosssections of roadways under current mining exploitation conditions in order to ensure the continuity and safety of mining facility operations. The existing methods of floor grinding were analyzed in terms of cost, labor intensity, safety, and environmental protection. The following section outlines the process of developing a mine floor grinding machine at Urządzenia i Konstrukcje Spółka Akcyjna, namely the stage of technical and marketing analysis is discussed, during which the needs and possibilities of implementing the floor grinding machine were assessed, as well as the process of preliminary research and design, construction and tests conducted on a prototype grinding machine. The operation of the floor grinder – which is driven by an electric motor to grind the elevated rock bed, load and transport the grinded rock to the hauling trucks, all performed by remote control – is described. In conclusion, the advantages of the Hydroma grinder are discussed, as it performs the work efficiently, effectively and safely, without exposing the environment to harmful emissions.
Access status: Open Access ,
Wpływ parametrów uskoku na zasięg jego oddziaływania
(Wydawnictwa AGH, 2011) Drzewiecki, Jan
In this article the method of estimation of range and intensity of fault impact is presented. From the practically point of view when the fault throw is comparable with height of longwall support there is a typical underground mining situation. On the other hand when the fault throw is higher than longwall face it will make an unfavorable situation. In each case the immediate vicinity of the fault or fault zones is characterized by anomalous in relation to the natural/gravity pressure condition. The vicinity of fault is a factor for weakening the rock mass. On the other hand the vicinity of the fault is an area of energy and stress concentration. This concentration in the vicinity of the fault combined with the energy accumulated in the range of longwall mining will determine the possibility of dynamic phenomena in hard coal seam as well as in the roof rocks. The proposed method also takes into account three parameters of fault: the faults throw h, the dip angle of the fault plane alpha and depth of hard coal seam H. The range of stress anomaly zones in the two walls of the fault is determined using a computer program developed by GIG called »SIGMA Z« for calculating the stress values using the formulas developed for calculating the values of the anomalous propagation velocity of longitudinal seismic wave in the analyzed area. Currently, this method is used in predicting stress distribution in the area of the mining activities.
Access status: Open Access ,
Zagrożenie tąpaniami a ryzyko zawodowe
(Wydawnictwa AGH, 2010) Drzewiecki, Jan
The underground mining is determined by particular environmental system which is connected with hazards on the different levels of influence for workers and working environment. Hazards in underground mines were dividing into hazards connected with mining machinery and mining systems and hazards which are connected with mining environment. In the paper are presented the elementary methods of estimate of occupational hazard. The main attention attends to rock burst hazard which is connected with mining environment and is an effect of underground mining. It is not fully possible to estimate of occupational risk connected with the symptoms of rock burst hazards. Data base in Central Mining Institute shows that in the underground mining are rock burst cases with apparent deficiencies symptoms like small energies and seismic activities or lack of strata movement. From this reason for rock burst hazard is estimate an occupational risk not as definitively set variable but as a variable change in the time. This change is effect of changes in a shape.