Comparison of rockburst occurrence during extraction of thick coal seams using top-coal caving versus slicing mining methods

2018 ◽  
Vol 55 (10) ◽  
pp. 1433-1450 ◽  
Author(s):  
Zhen-lei Li ◽  
Xue-qiu He ◽  
Lin-ming Dou ◽  
Da-zhao Song
Keyword(s):  
Conceptual Model ◽  
Extraction Process ◽  
Mining Method ◽  
Fracture Zones ◽  
Coal Seams ◽  
Prone Area ◽  
Mining Coal ◽  
Mine Openings ◽  
Method Of Extraction

In recent years, rockbursts have occurred frequently during the mining of thick coal seams in China. Use of the top-coal caving or slicing mining method to extract these thick seams may result in distinct geomechanical responses in the strata and, in turn, the pattern of rockburst occurrence around longwall layouts. To establish a thorough understanding of which method (caving or slicing) is better when it comes to preventing rockbursts during the extraction process, a suite of in situ rockburst measurements was conducted. Six typical rockburst-prone collieries were monitored during which a total of 110 rockburst events occurred. Numerical modelling was used to help interpret the observations. Here, we focus on the analysis of these field observations and the numerical simulations employed to develop a conceptual model for rockburst occurrence during caving mining of thick coal seams. We find that caving mining has a certain rockburst-reducing effect in that the method significantly decreases, or even avoids, the occurrence of rockbursts at coalfaces. Moreover, it reduces the scope of the damage likely to be incurred and the severity and frequency of rockbursting. According to the conceptual model, the rockburst-prone area during caving mining is generally the roadway section located a certain distance ahead of the coalface. This distance, which is roughly 10–54 m, is consistent with the rockburst damage observed on site (mostly 10–50 m ahead of the coalface). This rockburst pattern arises because caving mining results in reduced stress concentration, less bottom coal being retained, and wider-ranging fracture zones around the mine openings, especially ahead of the coalface. This makes the rock surrounding the mine openings less likely to accumulate high levels of elastic energy that need releasing and hence it is more difficult to induce rockbursting. Therefore, it is recommended that the top-coal caving method should be the preferred method of extraction when mining coal seams of a certain thickness.

scholarly journals Appendix: Economic Geology: Exploration for coal, oil and minerals

1997 ◽  
Vol 17 (1) ◽  
pp. 449-454 ◽  
Keyword(s):  
Academic Research ◽  
The Political ◽  
Geological Exploration ◽  
Coal Seams ◽  
Mineral Wealth ◽  
Political Implications ◽  
The Status ◽  
Comprehensive Survey ◽  
Mining Coal

AbstractThe incentive for most geological exploration has been related to the possibility of mineral wealth. Some has been undertaken by industry, other as a result of national interest. A great deal of academic research, particularly since 1960, has been financed by industry. It is impossible with financial pressures so strong to disentangle the presentation of research as between 'fundamental' and 'applied'. This section, summarizes the explicit search for hydrocarbons (coal and petroleum) and metalliferous and other minerals which in various ways has been alluded to in the preceding chapters. It is not intended as a comprehensive surveyCoal seams crop out extensively in Svalbard and, being conspic-uous in cliffs and talus, have been exploited in surface workings for fuel by whalers and hunters from the earliest days.The potential for mining and export and the political implications was increasingly realised from the later years of the Nineteenth Century. Until the status of Spitsbergen and Bjornoya was settled, coal was a political consideration and when the Treaty protected international commercial rights, economic facts slowly displaced political manoeuvring until the present situation where purely commercial considerations hardly make mining coal for export competitive. Coal occurrences may also have a potential for natural gas, possibly with similar competitive limitations with the present perception of offshore resources.Coal, being the only mineral effectively exploited, has focused research on coal-bearing strata. This review treats coal in situ from a stratigraphic-regional viewpoint beginning with the youngest seams. Further discussion in a stratigraphic context can be found

scholarly journals Improvement of Continuous Lateral Surface Mining Method for Coal Extraction from Closed Mines’ Pillars

2020 ◽  
pp. 542-562
Keyword(s):  
Dust Emission ◽  
Surface Mining ◽  
Economic Benefits ◽  
Coal Extraction ◽  
Mining Method ◽  
Coal Seams ◽  
Coal Deposits ◽  
Underground Mine Workings ◽  
Coal Pillars ◽  
Mining Coal

The presented paper deals with a continuous lateral method of closed mines' coal pillars surface mining and its advantages in land intensity, dust emissions, maximizing coal extraction, and overburden transporting costs. While inclined and steep coal seam strata in the pillars are widely exploited with land-and-cost intensive deepening longitudinal mining method, this article substantiates the choice of modification of block-and-layer continuous lateral mining method for different kinds of coal deposits. The aim of the study is to specify the modifications of the method proposed, define the stages of their carrying out, and emphasize the advantages over deepening longitudinal method of coal pillars surface mining. The basic principle of the proposed continuous lateral method of mining the coal pillars is limiting the final depth of quarry by the vertical height of the first floor of the underground mine workings. The continuous lateral mining method is detailed in the article in three modifications (for development coal seams strata of high and medium thickness, as well as distanced separate coal seams), which advantages are low land intensity and dust emission from the dump. Attention is also paid to the economic benefits of the block-and-layer continuous lateral method of mining coal pillars of closed mines, whereby the overburden transporting costs can be significantly reduced, while limitations of the proposed mining method concern specific sites of closed mines that make up a small part of the coal pillars extracted by surface mining today.

scholarly journals Intensification of the extraction process of phenolic compounds from Acorus calamus leaves

2021 ◽  
pp. 4-10
Author(s):  
Oleksiy Andryushayev ◽  
Olena Ruban ◽  
Yuliia Maslii ◽  
Inna Rusak
Keyword(s):  
Phenolic Compounds ◽  
Raw Materials ◽  
Extraction Process ◽  
Raw Material ◽  
Acorus Calamus ◽  
Optimal Conditions ◽  
Ultrasonic Action ◽  
Different Temperatures ◽  
Method Of Extraction ◽  
Temperature Time

The aim. To determine the intensified method of extraction of phenolic compounds from Acorus calamus leaves and optimal conditions for the process. Materials and methods. In order to develop the optimal intensified method of extraction samples were prepared in different conditions of raw materials-extractant ratio, temperature, time and multiplicity. As a raw materials spectrophotometrically pre-standardized Acorus calamus leaves were used. The extraction was carried out in a hermetically sealed ultrasonic extraction reactor PEX 1 (REUS, Contes, France). As the criteria of extraction efficiency were indicators of dry residue and total amount of flavonoids determined using methods described in State Pharmacopoeia of Ukraine. The amount of flavonoids was determined spectrophotometrically on a certified device Specord 200 (Analytik Jena, Germany). Results. According to our research results it was found that ultrasonic action and addition of surfactant significantly improves the efficiency of the extraction process. The optimal conditions for the process were determined. Experimentally proved that the rational raw material-extractant ratio is 1:15. Comparative study of the extraction process with different temperatures showed that the highest amount of extractives is achieved at temperature 70 °C and 45 min of duration. The optimal extraction multiplicity is 3. Conclusions. As a result of the study, the intensified extraction method for Acorus calamus leaves – re-maceration with ultrasound – was established. The conducted researches allowed to develop the method of extraction, expedient in the conditions of the modern pharmaceutical industry.

Comparison between the conventional method of extraction of essential oil of Laurus nobilis L. and a novel method which uses microwaves applied in situ, without resorting to an oven

2007 ◽  
Vol 1143 (1-2) ◽  
pp. 36-40 ◽  
Author(s):  
Guido Flamini ◽  
Marianna Tebano ◽  
Pier Luigi Cioni ◽  
Lucia Ceccarini ◽  
Andrea Simone Ricci ◽  
...  
Keyword(s):  
Essential Oil ◽  
Conventional Method ◽  
Laurus Nobilis ◽  
Novel Method ◽  
Method Of Extraction

Novel in situ production of smooth diamond films

1998 ◽  
Vol 13 (7) ◽  
pp. 1735-1737 ◽  
Author(s):  
Donald R. Gilbert ◽  
Dong-Gu Lee ◽  
Rajiv K. Singh
Keyword(s):  
Electron Cyclotron Resonance ◽  
Microwave Plasma ◽  
Ion Beam ◽  
Diamond Films ◽  
Extraction Process ◽  
Pure Oxygen ◽  
Average Roughness ◽  
Process System ◽  
Unique Method

We have developed a unique method to produce smooth diamond films using a modified microwave plasma process system. This method consists of sequential in situ deposition and planarization in an electron cyclotron resonance plasma system. Diamond films were deposited to a thickness of 3.0 μm in this system at a pressure of 1.000 Torr from gas mixtures of methanol and hydrogen. Deposition was followed by planarization using a two-grid ion beam extraction process with a pure oxygen plasma at 10 mTorr. The average roughness of the diamond films so produced was as low as 30 nm, which was a factor of two lower than that of the as-deposited diamond films.

scholarly journals Peculiarities of using classification indicators of the coal metamorphism degree for predicting the hazardous coal seams properties

2020 ◽  
Vol 201 ◽  
pp. 01014
Author(s):  
Mykola Antoshchenko ◽  
Elvira Filatieva ◽  
Vladyslav Yefimtsev ◽  
Vadym Tarasov
Keyword(s):  
Spontaneous Combustion ◽  
Chemical Activity ◽  
Mining Engineering ◽  
Coal Seams ◽  
Mining Operations ◽  
Emergency Situations ◽  
Specific Composition ◽  
Geological Conditions ◽  
Definition Of ◽  
Mining Coal

Currently, there is no reliable regulatory framework for determining the hazardous properties of coal seams, including the propensity of coal for spontaneous combustion. Under relatively identical mining engineering and geological conditions for mining coal seams, the probability of emergency situations is determined to a large extent by the genetic properties of coal. The research methodology is based on the classical definition of metamorphism, which characterizes the change in the composition and properties of coal. The analysis involves indicators that directly or indirectly characterize the elemental composition of organic and mineral mass, chemical activity and physico-mechanical properties. This will allow to establish a specific composition and properties that contribute to the manifestation of certain hazardous properties of coal seams during mining operations. It is shown that the modern industrial classification does not take into account the change in the organic and mineral constituents of coal, which does not make it possible to use it unchanged to predict the hazardous properties of coal seams.

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