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Abstract

This paper describes the concept of controlling the advancement speed of the shearer, the objective

of which is to eliminate switching the devices off to the devices in the longwall and in the adjacent

galleries. This is connected with the threshold limit value of 2% for the methane concentration in the

air stream flowing out from the longwall heading, or 1% methane in the air flowing to the longwall.

Equations were formulated which represent the emission of methane from the mined body of coal in the

longwall and from the winnings on the conveyors in order to develop the numerical procedures enabling

a computer simulation of the mining process with a longwall shearer and haulage of the winnings. The

distribution model of air, methane and firedamp, and the model of the goaf and a methanometry method

which already exist in the Ventgraph-Plus programme, and the model of the methane emission from the

mined longwall body of coal, together with the model of the methane emission from the winnings on

conveyors and the model of the logic circuit to calculate the required advancement speed of the shearer

together all form a set that enables simulations of the control used for a longwall shearer in the mining

process. This simulation provides a means for making a comparison of the output of the mining in the

case of work using a control system for the speed advancement of the shearer and the mining performance

without this circuit in a situation when switching the devices off occurs as a consequence of exceeding

the 2% threshold limit value of the methane concentration. The algorithm to control a shearer developed

for a computer simulation considers a simpler case, where the logic circuit only employs the methane

concentration signal from a methane detector situated in the longwall gallery close to the longwall outlet.

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Authors and Affiliations

Wacław Dziurzyński
Andrzej Krach
Teresa Pałka
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Abstract

The use of computer techniques at the design stage of industrial facilities is essential in modern times. The ability to shorten the time required to develop a project and assess the safety of the use of assumptions, often enables the reduction of the costs incurred in the future. The possibility to skip expensive prototype tests by using 3D prototyping is why it is currently the prevailing model in the design of industrial facilities, including in the mining industry. In the case of a longwall working, its stability requires the maintenance of the geometric continuity of floor rocks in cooperation with a powered roof support.

The paper investigates the problem of longwall working stability under the influence of roof properties, coal properties, shield loading and the roof-floor interaction. The longwall working stability is represented by an index, factor of safety (FOS), and is correlated with a previously proposed roof capacity index ‘g‘. The topic of the paper does address an issue of potential interest.

The assessment of the stability of the roof in longwalls was based on the numerical analysis of the factor of safety (FOS), using the Mohr-Coulomb stress criterion. The Mohr-Coulomb stress criterion enables the prediction of the occurrence of failures when the connection of the maximum tensile principal stress σ1 and the minimum compressive principal stress σ3 exceed relevant stress limits. The criterion is used for materials which indicates distinct tensile and compressive characteristics. The numerical method presented in the paper can be utilized in evaluating the mining natural hazards through predicting the parameters, which determine the roof maintenance in the longwall working.

One of the purposes of the numerical analysis was to draw attention to the possibilities that are currently created by specialized software as an important element accompanying the modern design process, which forms part of intelligent underground mining 4.0.

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Authors and Affiliations

Tomasz Janoszek
ORCID: ORCID
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Abstract

In longwall coal exploitation, problems with the proper functioning of the powered shield support often occur. In many cases, it results from the insufficient load-bearing capacity of the ground (floor) and the inability to achieve the set or yield pressure of the shield support. The improper functioning of the shield support may also result from its construction and the lack of optimisation to work effectively on a weak mine floor. This paper presents an attempt to optimise the operating conditions of the base of two-legged shield support based on the field observations and results of the PFC3D numerical calculation. In the framework of the numerical calculations, the impact of the width of the base and the location of the hydraulic legs on the working conditions of shield support on a weak floor were analysed.
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Authors and Affiliations

Sylwester Rajwa
1
ORCID: ORCID
Sven Bock
2
ORCID: ORCID

  1. Central Mining Institute (GIG), 1 Gwarków Sq., 40-166 Katowice, Poland
  2. DMT GmbH, Germany

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