Automation of the longwall mining system

Cost effective, safe, and technologically sound applications of automation technology to underground coal mining were identified. The longwall analysis commenced with a general search for government and industry experience of mining automation technology. A brief industry survey was conducted to identify longwall operational, safety, and design problems. The prime automation candidates resulting from the industry experience and survey were: (1) the shearer operation, (2) shield and conveyor pan line advance, (3) a management information system to allow improved mine logistics support, and (4) component fault isolation and diagnostics to reduce untimely maintenance delays. A system network analysis indicated that a 40% improvement in productivity was feasible if system delays associated with all of the above four areas were removed. A technology assessment and conceptual system design of each of the four automation candidate areas showed that state of the art digital computer, servomechanism, and actuator technologies could be applied to automate the longwall system

The Breaking Span of Thick and Hard Roof Based on the Thick Plate Theory and Strain Energy Distribution Characteristics of Coal Seam and Its Application

In mining engineering, the thick and hard roof threatens the safe production. Based on Reissner plate theory and combined with weighted residual method, with four edges clamped as the boundary conditions, this paper deduces the theoretical formula of the first breaking span of thick and hard roof. Based on Vlasov plate theory, with four edges simply supported as the boundary conditions, this paper deduces the theoretical formula of the periodic breaking span of thick and hard roof. The two formulas are used to verify the breaking span of thick and hard roof of Tashan Coal Mine, proving that its accuracy is higher than that of traditional beam theory. This paper studies the distribution characteristics of strain energy density in front of the coal seam during the mining process by numerical simulation, which is compared with the results of field microseismic experiments. It is found that the strain energy density of the coal seam has a good correlation with the probability of microseismic events. This paper provides theoretical support for more precise calculation of breaking span of the thick and hard roof and technical support for the practical stability analysis of the surrounding rock under the thick and hard roof

An Analysis of Stresses and Displacements around a Fault Plane Due to Longwall Face Advance in Coal Mining

This study has examined 3D stresses and displacements around a longwall mining system that is intercepted by a geological fault. More specifically, the study has analyzed the effect of a fault on longwall gate development entries, set-up rooms, T-junctions, and the longwall face as the longwall face progressed toward, through, and away from the fault. A general lithologic sequence and mining parameters related to the Herrin No. 6 coal seam in southern Illinois were employed. FLAC3D structural analysis code was used for simulating two (2) adjacent longwall faces. Linear elastic rock mass elements with non-linear elastic-plastic fault elements were analyzed using Hoek- Brown brittle failure criteria. Two (2) models were developed for analysis: a base elastic case without fault and an elastic model with elastic-plastic fault elements. Engineering properties for the rock mass strata were derived from a history of rock core testing and modified following the process indicated for Hoek’s Geologic Strength Index. Gob engineering properties and estimated load carrying capacities developed in earlier studies were used to make simulations physically realistic. The local tectonic (horizontal) stress field and vertical stress levels were applied to the simulation boundaries. Analysis data was extracted for several data lines in the roof and floor that were determined to be critical based on the geometry of the mine layout. Extracted data included 3D stresses and displacements with the Z-direction indicating vertical. This data was used to calculate vertical convergence and vertical and horizontal stress concentration variables VSCF, HSCF-XX, and HSCF-YY. Such data were developed for the longwall face advancing in 30-foot (10-m) increments away from the set-up room. Incremental displacements due to the fault proved to be more significant than changes in stress concentrations VSCF, HSCF-XX, and HSCF-YY. Set-up room X-displacements show a consistent increase in the fault case around 35%. Incremental Y-displacements vary sharply at first then changes quickly reduce to zero (0). Z-displacements were similar in both models. A fault oriented more vertically would have larger Z-displacement values. Gate X-displacements significantly decrease in the fault model until the face reaches 558 feet (170 m) from the starting point. Y-displacements show a rapid percentage rise in the fault model as the longwall face approaches the intersection of the fault with the first gate entry, but significant percentage decreases both before and after reaching this intersection. Significant increases in Z-displacements occur as the face approaches and leaves the intersection of the fault with the gate entries. Around the fault, the first row of gate pillars experiences a change in horizontal displacements HSCF-XX and HSCF-YY of approximately 10%. Second row pillars also see a change in HSCF-XX of around 10%, but not a significant change in HSCF-YY. Gate entry VSCF values show significant increases at the fault intersection until the face passes the gate/fault intersection

Soft Roof Failure Mechanism and Supporting Method for Gob-Side Entry Retaining

To study the soft roof failure mechanism and the supporting method for a gateway in a gently inclined coal seam with a dip angle of 16° kept for gob-side entry retaining, and through the methodology of field investigation and numerical and analytical modeling, this paper analyzed the stress evolution law of roof strata at the working face end and determined that the sharp horizontal stress unloading phenomenon along the coal wall side did not appear after the working face advanced. Conversely, the horizontal stress along the gob side instantly decreased and the tensile stress produced, and the vertical stress in the central part of the roof had a higher reduction magnitude as well. An in-depth study indicates that the soft roof of the working face end subsided and seriously separated due to the effect of the front abutment pressure and the roof hanging length above the gob line, as well as certain other factors, including the rapid unloading of the lateral stress, tension and shear on the lower roof rock layer and dynamic disturbance. Those influencing factors also led to rapid crack propagation on a large scale and serious fracturing in the soft roof of the working face end. However, in the gob stress stabilized zone, the soft roof in the gob-side entry retaining has a shearing failure along the filling wall inside affected by the overburden pressure, rock bulking pressure, and roof gravity. To maintain the roof integrity, decrease the roof deformation, and enable the control of the working face end soft roof and the stabilization of the gob-side entry retaining roof, this study suggests that the preferred bolt installation angle for the soft roof situation is 70° based on the rock bolt extrusion strengthening theory

Applicability of siberian placer mining technology to Alaska

The result of Perestroyka and Glasnost has been an awakening of potential for cooperation between East and West. Nowhere has that been better demonstrated than between Alaska and Magadan Province, USSR. This report summarizes a one year effort financed by ASTF, with participation from several technical organizations, to establish contacts with the Siberian placer mining industry. The purpose of the project was to provide initial assessment of the Soviet technology for placer mining in permafrost. A ten day trip to Magadan province by an ASTF team and a similar length visit to Alaska by the Soviet mining group representing the All Union Scientific and Research Institute of Gold and Rare Metals, (VNII-I), Magadan are described. The report also reviews translated data on mining in permafrost and describes surface and underground placer mining technology developed by the Soviets. The report also lists relevant publications on Soviet mining research and state of the art Soviet mining technology and expertise

Technology Diffusion in the Coal Mining Industry of the USSR: An Interim Assessment

Over many years IIASA has been involved in energy studies, coal was always an important research topic at all levels from resource assessment, study of potential future coal supply to the analysis of environmental impacts resulting from expanded coal utilization. The present paper presents an analysis of technological change in the coal mining industry of the USSR. It describes within a quantitative framework first the evolution of the coal mining industry in general, based on macro indicators of output, production intensity and labor productivity. Then it describes qualitatively the different historical phases of development and introduction of new technologies into the sector and concludes by quantifying the historical trajectories of new technologies diffusion, using standard models of technological diffusion and substitution. The paper not only provides insight into the dynamics of the technological change in the coal mining industry of the USSR, but addresses also some of the effects of theses developments. Finally some tentative conclusions with respect to future evolution in the industry are outlined. Other IIASA studies have addressed similar changes in the technology of coal mining in the USA the UK and the FRG, albeit in not such great detail. These results could be used in conjunction with the present study for a subsequent cross national comparison of technological trends in the coal mining industry. The present paper is the product of a continued and very fruitful cooperation between IIASA and the Academy of the National Economy at the Council of Ministers of the USSR. It adds to the productivity of this cooperation, which will continue in the future

Technology Diffusion in the Coal Mining Industry of the USSR: An Interim Assessment

Over many years IIASA has been involved in energy studies, coal was always an important research topic at all levels from resource assessment, study of potential future coal supply to the analysis of environmental impacts resulting from expanded coal utilization. The present paper presents an analysis of technological change in the coal mining industry of the USSR. It describes within a quantitative framework first the evolution of the coal mining industry in general, based on macro indicators of output, production intensity and labor productivity. Then it describes qualitatively the different historical phases of development and introduction of new technologies into the sector and concludes by quantifying the historical trajectories of new technologies diffusion, using standard models of technological diffusion and substitution. The paper not only provides insight into the dynamics of the technological change in the coal mining industry of the USSR, but addresses also some of the effects of theses developments. Finally some tentative conclusions with respect to future evolution in the industry are outlined. Other IIASA studies have addressed similar changes in the technology of coal mining in the USA the UK and the FRG, albeit in not such great detail. These results could be used in conjunction with the present study for a subsequent cross national comparison of technological trends in the coal mining industry. The present paper is the product of a continued and very fruitful cooperation between IIASA and the Academy of the National Economy at the Council of Ministers of the USSR. It adds to the productivity of this cooperation, which will continue in the future

Survey on roof movement of the gangue backfill working face

This paper studied the roof movement characteristics of LW1302N-1 with gangue backfill mining in Shandong Xinjulong Company of China. The monitoring of roof subsidence of the gob and bearing stress of filled gangue was carried out by using the roof subsidence and gangue loading monitoring system. From data analysis, the result shows that: (1) Gob roof subsidence can be divided into six stages including slow subsidence, fast subsidence, very fast subsidence, subsidence slowing down, subsidence speeding up and subsidence becoming slow. (2) Filled gangue loading period can be divided into four stages including slow increasing resistance, fast increasing strength, strengthening and continuing increasing resistance, Similarly, the gob roof movement consists of four steps such as immediate roof caving, central roof flexure, main roof fracturing, and high strata flexure. (3) The immediate roof is 3.1 times the thickness of equal mining height, and the main roof is 2.7 times the thickness of equal mining height. The research results provide a reference to the analysis of the characteristics of overlying strata structure and roof movement for gangue backfill mining in deep coal mines