Research on Mechanism of Roof Caving in Gob-Side Entry Retaining in Upper Roadway within Inclined Coal Seam

2021 ◽  
Vol 09 (02) ◽  
pp. 138-147
Author(s):  
少旭 吴
Keyword(s):  
Coal Seam ◽  
Roof Caving

Numerical Simulation of Underground Pressure in Mining High-Inclined Coal-Seam with Analysis of Material Properties in Mine Dongbaowei

2013 ◽  
Vol 644 ◽  
pp. 382-386 ◽  
Author(s):  
Ming Ming Wen
Keyword(s):  
Coal Seam ◽  
In Situ Observation ◽  
Coal Seams ◽  
Relevant Model ◽  
Roof Caving ◽  
Deformation Feature ◽  
Working Face ◽  
Strata Behavior ◽  
Surrounding Rock Stress

The FLAC software is used in establishing a relevant model to study the strata behavior of fully mechanized working face of steep coal seams. Using this model, we have simulated the roof caving characteristic and the stress distribution of surrounding rocks and analyzed the deformation feature of the surrounding rocks in the working face end. Based on the in-situ observation about the fully mechanized working face, we have obtained the surrounding rock stress and the strata behavior of steep coal seam and proposed some countermeasures aiming at these problems.

scholarly journals Geophysical Evaluation of Effectiveness of Blasting for Roof Caving During Longwall Mining of Coal Seam

2019 ◽  
Vol 177 (2) ◽  
pp. 905-917 ◽  
Author(s):  
Łukasz Wojtecki ◽  
Petr Konicek ◽  
Maciej J. Mendecki ◽  
Iwona Gołda ◽  
Wacław M. Zuberek
Keyword(s):  
Coal Seam ◽  
Stress Drop ◽  
Longwall Mining ◽  
High Energy ◽  
Longwall Face ◽  
Seismic Moment Tensor ◽  
Coal Seams ◽  
Rockburst Hazard ◽  
Roof Caving ◽  
Roof Rocks

Abstract Deep longwall mining of coal seams is made in the Upper Silesian Coal Basin (USCB) under complicated and mostly unfavourable geological and mining conditions. Usually, it is correlated with rockburst hazard mostly at a high level. One of the geological factors affecting the state of rockburst hazard is the presence of competent rocks in the roof of extracted coal seams, so rock falling behind the longwall face does not occur, and hanging-up of roof rocks remains. The long-lasting absence of caving may lead to an occurrence of high-energy tremor in the vicinity of the longwall face. Roof caving behind the longwall face may be forced by blasting. The column of explosives is then located in blastholes drilled in layers of roof rocks, e.g. sandstones behind the longwall face. In this article, a characterization of tremors initiated by blasts for roof caving during underground extraction of coal seam no. 507 in one of the collieries in the USCB has been made using three independent methods. By the basic seismic effect method, the effectiveness of blasting is evaluated according to the seismic energy of incited tremors and mass of explosives used. According to this method, selected blasts gave extremely good or excellent effect. An inversion of the seismic moment tensor enables determining the processes happening in the source of tremors. In the foci of provoked tremors the slip mechanism dominated or was clearly distinguished. The expected explosion had lesser significance or was not present. By the seismic source parameters analysis, among other things, an estimation of the stress drop in the focus or its size may be determined. The stress drop in the foci of provoked tremors was in the order of 105 Pa and the source radius, according to the Brune’s model, varied from 44.3 to 64.5 m. The results of the three mentioned methods were compared with each other and observations in situ. In all cases the roof falling was forced.

scholarly journals Regularities in formation of stressed state in roof rocks of mined-out space during development stage

2022 ◽  
pp. 68-75
Author(s):  
V.N. Zakharov ◽  
V.A. Trofimov ◽  
A.V. Shlyapin
Keyword(s):  
Coal Seam ◽  
Development Stage ◽  
Stress And Strain ◽  
Formation Water ◽  
Variable Theory ◽  
Complex Variable Theory ◽  
Compressive Stresses ◽  
Roof Caving ◽  
Deformation Processes ◽  
Roof Rocks

Formation of the stress-and-strain state of the rock mass in the roof of mined coal seam depends on the development of the mined-out space. It is believed that the coal seam is located deep enough and it can be assumed that the effect of the daylight surface on its condition can be neglected. In this case, the solution is based on the analytical approach using methods of the complex variable theory and it is reduced to the construction of a single permission analytical function. The paper reviews the evolution of the deformation processes in development of the mined-out space in presence of a hard-to-collapse elastic roof, which is capable of sinking smoothly over time, without sudden caving on the landings on the floor. A particular attention is paid to the phase when the roof and the floor touch each other, i.e. the roof caving, starting from the first touching and up to its complete caving. In this case, two sections of the hanging roof are formed, that are gradually reducing in length as the dimensions of the mined-out space increase. The area of roof caving is progressively increasing, and the vertical compressive stresses at the boundary are gradually rising, tending to reach the initial vertical pressure at the depth of the formation before the start of its mining. Tension zones relative to the horizontal and vertical stresses are identified, that are attributed to the areas of roof hang-up, which may determine the location of zones with higher methane and formation water permeability, both in the rocks between the seams and in the coal seam.

The Detection Research of Roadway Roof Strata Structure in Coal Seam

2013 ◽  
Vol 734-737 ◽  
pp. 677-681
Author(s):  
Qing Xiang Zhang ◽  
Hou Sheng Jia ◽  
Long Fan ◽  
Xi Dong Zhao ◽  
Zhi Gang Wang ◽  
...  
Keyword(s):  
Coal Seam ◽  
Engineering Practice ◽  
Theory Analysis ◽  
Coal Roadway ◽  
Roof Caving ◽  
Instability Theory ◽  
Rock Structure ◽  
Roof Strata ◽  
Good Agreement ◽  
Main Factor

Through the structure instability theory analysis of the coal roadway roof ,the author concluded that mechanical properties of rock, location, thickness and thickness ratio is the main factor affecting the instability and failure of rock structure. Capitalize on the roof caving hidden danger detector developed by the China university of mining and technology to synchronize, continuous and intensive monitor the rotational speed, thrust for synchronization and thrust. Based on the record ,the author inferred the coal seam roof lithology and rock structures of the different drilling location. Engineering practice shows that the use of roof caving hidden danger detector to identify lithology of strata and structure is in good agreement with the core test values. Coincidence rate reached 95.14% and the recognition effect is quite good.

Phosphorus minerals in tonstein; coal seam 405 at Sośnica-Makoszowy coal mine, Upper Silesia, southern Poland

2013 ◽  
Vol 63 (2) ◽  
pp. 271-281 ◽  
Author(s):  
Magdalena Kokowska-Pawłowska ◽  
Jacek Nowak
Keyword(s):  
Trace Elements ◽  
Coal Seam ◽  
Mineral Composition ◽  
Coal Mine ◽  
Chemical Compositions ◽  
Coal Basin ◽  
Upper Silesia ◽  
Southern Poland ◽  
Basin Area

Abstract Kokowska-Pawłowska, M. and Nowak, J. 2013. Phosphorus minerals in tonstein; coal seam 405 at Sośnica- Makoszowy coal mine, Upper Silesia, southern Poland. Acta Geologica Polonica, 63 (2), 271-281. Warszawa. The paper presents results of research on tonstein, which constitutes an interburden in coal seam 405 at the Sośnica- Makoszowy coal mine, Makoszowy field (mining level 600 m), Upper Silesia, southern Poland. The mineral and chemical compositions of the tonstein differ from the typical compositions described earlier for tonsteins from Upper Silesia Coal Basin area. Additionally, minerals present in the tonsteins include kaolinite, quartz, kaolinitised biotite and feldspars. The presence of the phosphatic minerals apatite and goyazite has been recognized. The presence of gorceixite and crandallite is also possible. The contents of CaO (5.66 wt%) and P2O5 (6.2 wt%) are remarkably high. Analysis of selected trace elements demonstrated high contents of Sr (4937 ppm) and Ba (4300 ppm), related to the phosphatic minerals. On the basis of mineral composition the tonstein has been identified as a crystalline tonstein, transitional to a multiplied one.

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