scholarly journals On the relationship between gas emission from undermined coal-bearing stratum and the intensity of coal seam mining

2021 ◽  
Vol 280 ◽  
pp. 08017
Author(s):  
Sergei Mineev ◽  
Elvira Filatieva ◽  
Aleksandr Oleinichenko ◽  
Mihaela Toderas
Keyword(s):  
Unit Area ◽  
Active Movement ◽  
Gas Release ◽  
Coal Seams ◽  
Theoretical Scheme ◽  
Geological Conditions ◽  
Characteristic Points ◽  
Seam Mining ◽  
The Relationship ◽  
Excavation Site

A theoretical scheme of gas release from the coalbed under production by treatment workings has been developed. The sizes of zones of different intensity of gas release from the working thickness are set according to the characteristic points of muld shift of the earth's surface. Total amount of releasing gas is determined by the area of the developed space, over which there is an intensive movement of the mined coal. The formation of this area is associated with the development of cleaning operations within the boundaries of the excavation site and the speed of movement of the treatment face. During the development of the theoretical scheme, several assumptions were made, the validity of which was verified on the basis of experimental data obtained in the conditions of four mines at fifteen excavation sites. Coal seams with coals of grades G and A were worked out by them at a depth of 300-1195 m, the capacity of coal seams was 0.90-2.20 m, cleaning works were carried out at a depth of 300-1195 m, the length of the lavas was in the range of 74÷270 m. The monthly movement of the treatment faces and the amount of gas released during this period were taken into account for each excavation site. It is established that the relative gas release per unit area of the developed space remains a fairly constant value for some mining and geological conditions, if the total amount of gas is attributed to the area that determines the active movement of rocks over a moving treatment face. This allows you to use the previously obtained results of determining the categorical danger of mines by relative gas release per ton of coal production in terms of improving the forecast of gas release from the coalbed under production more efficiently.

Recent Patents on Thin Coal Seam Mining Equipment

2020 ◽  
Vol 13 (2) ◽  
pp. 99-108
Author(s):  
Yanxiang Wang ◽  
Daolong Yang ◽  
Bangsheng Xing ◽  
Tingting Zhao ◽  
Zhiyi Sun ◽  
...  
Keyword(s):  
Coal Seam ◽  
Underground Space ◽  
Mining Method ◽  
Mining Equipment ◽  
Coal Seams ◽  
Thin Coal Seam ◽  
Recoverable Reserves ◽  
Working Face ◽  
Geological Conditions ◽  
Seam Mining

Background:: China's thin and extremely thin coal seam resources are widely distributed and rich in reserves. These coal seams account for 20% of the recoverable reserves, with 9.83 billion tons of industrial reserves and 6.15 billion tons of recoverable reserves. Objective: Due to the complex geological conditions of the thin coal seam, the plow mining method cannot be effectively popularized, and the drum mining method is difficult to be popularized and applied in small and medium-sized coal mines, so it is necessary to find other more advantageous alternative mining methods. Methods: The equipment integrates mining operations, conveying operations, and supporting operations, and is suitable for mining short and extremely thin coal seam with a height of 0.35m-0.8m and width of 2m-20m. It has the advantages of the low body of the shearer, no additional support on the working face, and small underground space. The mining efficiency of thin coal seam and very thin coal seam can be improved and the mining cost can be reduced. Results: Thin coal seam shear mining combines mining, conveying, and supporting processes together and has the advantages of a low fuselage, no extra support required for the working face, and feasibility in a small underground space. Conclusion: The summarized mining method can improve the mining efficiency of thin and extremely thin coal seams, reduce mining costs, and incorporate green mining practices, which take both mining economy and safety into account.

scholarly journals Control of the Internal and External Staggered Distance of Coal Mining Face to the Water-Conducting Fissures in the Overlying Strata of the Near Coal

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zhiyuan Jin ◽  
Tao Peng
Keyword(s):  
Coal Seam ◽  
Coal Mining ◽  
Coal Mine ◽  
Calculation Formula ◽  
Coal Seams ◽  
Coal Face ◽  
Geological Conditions ◽  
Mining Face ◽  
Seam Mining ◽  
Water Proof

In Northwest China, rainfall is low, water resources are scarce, and the ecological environment is fragile. For shallow-buried and close-spaced coal seams with a thickness of upper coal bed >60∼70 m, the water-conducting fissures of the overlying rock will not penetrate the water-isolating layer after the upper coal seam is mined; the internal and external gap angles of the water-conducting fissures are not generated from the water-isolating layer. We set out to explore the critical internal and external dislocations for the second significant development of water-conducting fissures in the overlying rock after coal mining under control. A calculation model for the critical internal and external staggered distances of coal mining face in shallow-buried and close-spaced coal seams is established, the calculation formula is given, and the calculation formula for the critical seam mining ratio under the condition of internal staggered mining mode is given. Numerical simulation performed by UDEC methods: taking the overburden strata in the shallow-buried and close-spaced coal seam mining area of Shigetai Coal Mine as a prototype, it was verified that the critical internal and external offsets of the coal mining face in shallow-buried and close-spaced coal seams have a significant effect on the overlying water flow cracks in the mining of the lower coal seam. For the feasibility of developmental control, according to the engineering geological conditions of Shigetai, through the calculation method of external staggered distance, it is concluded that the distance of the open cut of the lower coal face and the upper coal face is only 21∼27 m, which is much smaller than the water barrier. It does not produce the critical distance of the water-conducting cracks. Therefore, in the process of mining the lower coal seam, the water-proof layer will produce water-conducting cracks, lose its water-proof performance, and cause water loss. This is also the cause of the water inrush accident in Shigetai Coal Mine.

Economic and Technical Analysis of Thick Coal Seam Mining Methods

2012 ◽  
Vol 170-173 ◽  
pp. 872-875
Author(s):  
Xiang Min Zhao ◽  
Peng Yang
Keyword(s):  
Surface Mining ◽  
Economic Security ◽  
Open Pit ◽  
Open Pit Mining ◽  
Coal Seams ◽  
Operating Personnel ◽  
Thick Coal Seam ◽  
Geological Conditions ◽  
Mining Methods ◽  
Seam Mining

Common mining methods for thick coal seams or extremely thick coal seams has slice mining top coal caving mining, greater height mining, and surface mining. From the perspective of economic and technological mining method, the choice of methods should be fully taken into account the technical, economic, quality of operating personnel, equipment, geological conditions. It allows priority to open-pit mining, and then according to the thickness, coal quality, coal other factors to select the top coal caving or mining of high extraction methods which can achieve the economic, security, and efficient purposes. Conversely, if the method is poor choice, it will certainly lead to economic and time losses.

scholarly journals Time Series Effect on Surface Deformation above Goaf Area with Multiple-Seam Mining

Symmetry ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1428
Author(s):  
Zhenyue Shi ◽  
Qingbiao Wang ◽  
Pu Wang ◽  
Donglin He ◽  
Yun Bai ◽  
...  
Keyword(s):  
Coal Mining ◽  
Surface Deformation ◽  
Ground Subsidence ◽  
Lagrangian Analysis ◽  
Large Area ◽  
Coal Seams ◽  
Near Surface ◽  
Geological Conditions ◽  
Mining Sequence ◽  
Seam Mining

The surface subsidence caused by coal mining is a large area, and computer simulation is a fast and intuitive method, which can help us understand the macroscopic subsidence law. The mined-out area left over by coal mining is not disposed of appropriately for a long time. Thus, it can easily cause ground subsidence, collapse, or spot cracking, especially when mining multiple coal seams, which seriously restricts the construction and safety of the near-surface rock and soil layers. Based on the engineering background of five-layer coal mining in the Beibu Coal Mine of Laiwu City, a “Fast Lagrangian Analysis of Continua in 3D” numerical calculation model was established. The model was used to analyze the surface deformation indexes of four groups with different mining sequences in multiple coal seams, revealing the sequence effects of mining time on the surface deformation law in the goaf collapse areas, hence obtaining optimal mining sequences. The results showed that the four groups of mining sequences (including vertical settlement and horizontal deformation) have stable surface deformation centers, but the deformation ranges and amounts are quite different. The settlement deformation is the main difference. Mining sequence I has the largest deformation of 62.7 cm, followed by mining sequence III. Mining sequences II and IV are basically the same, at only 22% of the value of mining sequence 1. A multi-index analysis of the surface deformation curve including the inflection point, stagnation point, and slope showed that the larger the surface deformation, the more evident the change of the curve (concave or convex) and slope, the more uneven the foundation stress, the more severe the damage to the surface structures, and the less suitable the surface construction. Finally, upon analyzing the indicators of surface stability and adaptability, mining sequence IV was indicated as the optimal scheme. It is suggested that an optimal mining sequence should be appropriately selected before the mining of multiple coal seams. The research results can provide effective guidance for addressing surface deformations under similar geological conditions, and can provide scientific evaluations for the safety and stability of surface buildings and structures, leading to considerable economic and social benefits.

Radiation Damage, Contrast and Statistics in High Resolution Biological Electron Microscopy

1970 ◽  
Vol 28 ◽  
pp. 260-261
Author(s):  
Robert M. Glaeser
Keyword(s):  
High Resolution ◽  
Particle Flux ◽  
Unit Area ◽  
Signal To Noise ◽  
Resolution Image ◽  
High Resolution Image ◽  
Pass Through ◽  
Counting Statistics ◽  
The Relationship ◽  
Picture Element

It is well known that a large flux of electrons must pass through a specimen in order to obtain a high resolution image while a smaller particle flux is satisfactory for a low resolution image. The minimum particle flux that is required depends upon the contrast in the image and the signal-to-noise (S/N) ratio at which the data are considered acceptable. For a given S/N associated with statistical fluxtuations, the relationship between contrast and “counting statistics” is s131_eqn1, where C = contrast; r2 is the area of a picture element corresponding to the resolution, r; N is the number of electrons incident per unit area of the specimen; f is the fraction of electrons that contribute to formation of the image, relative to the total number of electrons incident upon the object.

IMPROVEMENT OF SPRING DURUM WHEAT SELECTION METHODOLOGIES UNDER CLIMATE CHANGE CONDITIONS

1970 ◽  
pp. 33-36
Author(s):  
А. I. Grabovets ◽  
V. P. Kadushkina ◽  
S. А. Kovalenko
Keyword(s):  
Grain Yield ◽  
Durum Wheat ◽  
Correlation Coefficient ◽  
Harvest Index ◽  
Unit Area ◽  
Correlation Coefficients ◽  
Chemical Mutagenesis ◽  
Main Method ◽  
The Relationship ◽  
Selection Of

With the growing aridity of the climate on the Don, it became necessary to improve the methodology for conducting the  breeding of spring durum wheat. The main method of obtaining the source material remains intraspecific step hybridization. Crossings were performed between genetically distant forms, differing in origin and required traits and properties. The use of chemical mutagenesis was a productive way to change the heredity of genotypes in terms of drought tolerance. When breeding for productivity, both in dry years of research and in favorable years, the most objective markers were identified — the size of the aerial mass, the mass of grain per plant, spike, and harvest index. The magnitude of the correlation coefficients between the yield per unit area and the elements of its structure is established. It was most closely associated with them in dry years, while in wet years it decreased. Power the correlation of the characteristics of the pair - the grain yield per square meter - the aboveground biomass averaged r = 0.73, and in dry years it was higher (0.91) than in favorable ones (0.61 - 0.70) , between the harvest and the harvest index - r = 0.81 (on average). In dry years, the correlation coefficient increased to 0.92. Research data confirms the greatest importance of the mass of grain from one ear and the plant in the formation of grain yield per unit area in both dry and wet years. In dry years, the correlation coefficient between yield and grain mass per plant was on average r = 0.80; in favorable years, r = 0.69. The relationship between yield and grain mass from the ear was greater — r = 0.84 and r = 0.82, respectively. Consequently, the breeding significance of the aboveground mass and the productivity of the ear, as a criterion for the selection of the crop, especially increases in the dry years. They were basic in the selection.

scholarly journals Tropism of Sub-Axial Cervical Facet Joints Is Not Related to Segmental Movement during Active Movement or Therapist-Perceived Symptomatic Locations

Symmetry ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 739
Author(s):  
Neil Tuttle ◽  
Kerrie Evans ◽  
Clarice Sperotto dos Santos Rocha
Keyword(s):  
Cervical Spine ◽  
Neck Pain ◽  
Active Movement ◽  
Facet Joints ◽  
Segmental Mobility ◽  
Limited Mobility ◽  
Translational Movement ◽  
The Difference ◽  
Cervical Facet ◽  
The Relationship

Tropism, or asymmetry, of facet joints in the cervical spine has been found to be related to degenerative changes of the joints and discs. Clinicians often assume that differences in segmental mobility are related to tropism. The aims of this study were to determine the relationship between asymmetry of facet joints in the sub-axial cervical spine and (1) segmental mobility and (2) spinal levels perceived by therapists to have limited mobility. Eighteen participants with idiopathic neck pain had MRIs of their cervical spine in neutral and at the end of active rotation. Angular movement and translational movement of each motion segment was calculated from 3D segmentations of the vertebrae. A plane was fitted to the facet on each side. Tropism was considered to be the difference in the orientation of the facet planes and ranged from 1 to 30° with a median of 7.7°. No relationships were found between the extent of tropism and either segmental movement or locations deemed to be symptomatic. Tropism in the sub-axial cervical spine does not appear to be related to segmental mobility in rotation or to levels deemed to be symptomatic.

Reasonable Entry Layout of Lower Seam in Multi-Seam Mining Based on Numerical Simulation

2013 ◽  
Vol 295-298 ◽  
pp. 2980-2984
Author(s):  
Xiang Qian Wang ◽  
Da Fa Yin ◽  
Zhao Ning Gao ◽  
Qi Feng Zhao
Keyword(s):  
Numerical Simulation ◽  
Stress Distribution ◽  
Coal Seam ◽  
Coal Mine ◽  
Abutment Pressure ◽  
Surrounding Rock ◽  
Geological Conditions ◽  
Seam Mining

Based on the geological conditions of 6# coal seam and 8# coal seam in Xieqiao Coal Mine, to determine reasonable entry layout of lower seam in multi-seam mining, alternate internal entry layout, alternate exterior entry layout and overlapping entry layout were put forward and simulated by FLAC3D. Then stress distribution and displacement characteristics of surrounding rock were analyzed in the three ways of entry layout, leading to the conclusion that alternate internal entry layout is a better choice for multi-seam mining, for which makes the entry located in stress reduce zone and reduces the influence of abutment pressure of upper coal seam mining to a certain extent,. And the mining practice of Xieqiao Coal Mine tested the results, which will offer a beneficial reference for entry layout with similar geological conditions in multi-seam mining.

ANALYSIS OF PRODUCTION RISK FROM CRUSHES OF ROCKS AT EXCAVATION SITES, TAKING INTO ACCOUNT WAYS OF PROTECTION

2021 ◽  
pp. 124-134
Author(s):  
Iaroslav Liashok ◽  
◽  
Serhii Podkopaiev ◽  
Yuliia Simonova ◽  
Hennadii Boichenko ◽  
...  
Keyword(s):  
Practical Significance ◽  
Production Risk ◽  
Venn Diagrams ◽  
Deep Coal Mine ◽  
Geological Conditions ◽  
Rock Collapse ◽  
Available Information ◽  
Decision Making Model ◽  
Excavation Site ◽  
Industrial Risk

Purpose. To assess the production risk of rock collapse in a deep coal mine to identify hazards in the workplaces of the excavation site, taking into account different methods of protection of workings. Methods. A comprehensive approach was used, which included: analysis and generalization of known research; expert evaluation; use of the basic provisions of probability theory and set algebra (Venn diagrams), the method of estimating the production risk of Fine-Kinney; processing, analysis and interpretation of the obtained results. Results. Problems and sources of industrial risk from rock collapses during maintenance of workings, risk-forming factors that contribute to the threat of dangerous events at the excavation site are analyzed. The decision-making model is considered, which is based on the description of situations when the production risk of the dangerous factor “landslides and collapses” in the maintenance of preparatory workings depends on the result of choosing an alternative method of protection of the retractable lane. For excavation sites under the same mining and geological conditions for all workplaces, the probability of receiving consequences from dangerous events due to uncertain conditions of their implementation has been established. It is fixed that the realization of this production risk is influenced by low reliability and inefficiency of the practiced methods of protection of excavations. Risk analysis is defined as the systematic use of available information to identify hazards in the maintenance of long workings. Novelty. A model for monitoring the production risk of rock collapses in excavations of deep coal mines is proposed, which allows assessing the dynamics of the threat at the stage of technical decisions related to the choice and justification of the method of protection of workings taking into account the interaction of risk factors. Practical significance. When formulating measures to reduce the risk of dangerous events at the excavation site, it is necessary to take into account that the production risk of rock collapse while maintaining the workings depends largely on the method of protection and effectiveness of technological measures.

The relationship between crop yield (or mean plant weight) of lettuce and plant density, length of growing period, and initial plant weight

1976 ◽  
Vol 86 (1) ◽  
pp. 83-91 ◽  
Author(s):  
M. A. Scaife ◽  
D. Jones
Keyword(s):  
Time Course ◽  
Plant Density ◽  
Unit Area ◽  
Subterranean Clover ◽  
Plant Weight ◽  
Relative Growth ◽  
Growing Period ◽  
Lettuce Growth ◽  
Log Linear ◽  
The Relationship

SUMMARYLettuce obeys the Shinozaki–Kira relationship in which the reciprocal of plant weight is linearly related to plant density. The intercept (a) represents the reciprocal of the weight of an isolated plant and the slope (b) represents the reciprocal of yield/unit area at high densities (the ‘ceiling yield’). This work examines the time course of (a) and (b) in an ‘ideal environment’ in which water and nutrients are non-limiting, and the light/temperature regime is constant.Two pot experiments are described: the first showed that the growth of isolated lettuces follows a logistic expression, which can therefore be substituted for a–1 in the Shinozaki-Kira equation. It was then hypothesized that b–1, the ‘ceiling yield’ would be constant over time. This was confirmed by the second experiment, giving the equationw–1t = w–10 e1–kt × w–1max × bd,in which wt is mean plant weight at time t, w0 and wmax are the initial and final weights of isolated plants, k is the early relative growth rate of such plants, b–1 is the constant ceiling yield, and d is the plant density.Two examples of the use of the equation are given: one shows how it predicts the interaction between seed size and plant density within a species (subterranean clover): the other illustrates how it can be used to explain why lettuce growth appears to be log-linear against time whereas cereal growth is more nearly just linear.

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