Archives of Mining Sciences

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.

In view of the permanent increase of the municipal solid waste incineration (MSWI) residues amount,

the numerous attempts to find a way of their recovery have been undertaken. In this paper the idea of the

recovery of the MSWI residues in Kłodawa salt mine is presented. The idea is to fill the waste in underground

workings, close and/or backfill the underground excavations with self-solidifying mixture prepared

on the basis of MSWI grained solid residues. Two techniques are proposed: 1) hydraulic backfill technique

(HBT) where the mixture is prepared in the surface installation and pumped down into the underground

workings through shaft and the pipelines and 2) dry waste technique (DWT), where dry grained waste is

dropped into the mine by pneumatic pipeline transport, then supplied to the underground mixture-preparing-

installation and pumped as a thin liquid or paste into the selected workings. The description of the

technology is preceded by general characteristic of the hardening backfill in underground mines and by

characteristic of MSWI residues, drafted on the basis of the literature review.

The article contains considerations on possible actions directed at increasing productivity of hard

coal mining industry. It is necessary to improve the state of the industry, and ensure its survival. Basic

definitions and measures concerning productivity and management were presented to illustrate examples

referring to a mining enterprise. Then, basing on organizing, one of the management functions, the issue

of productivity in a mining enterprise and its influence on improving effectiveness of operational management,

was analysed. An assumption was presented that solutions concerning identification of sources

and volume of costs, hitherto existing in mining enterprises, ought to be complemented with the planning

function following process approach. It can be the starting point for decisions of economic feasibility of

given deposits, seams or parts of them, before mining operations start, and to control incurred costs in

process approach. The article is summed up with a process algorithm of cost management.

The brake linkage of a hoisting machine is a very important component determining the safety of

the hoisting machine’s entire braking system. It is subject to weekly inspections. However, an efficiency

test of brake performance is carried out every 6 months. Once every 3 years, a test must be carried out by

an appraiser who pays particular attention to the executive and control components of the brakes as well

as the strain - brake system and brake release components. The legal provisions regulating the testing

of braking system linkages are not precise. So far, the control has been based on random measurement

of strains using electrical resistance strain gauges stuck to the surface of the linkage. A new method

for measuring the strains of the linkage has been proposed in the work. It is based on fibre optic strain

sensors with Fibre Bragg Gratings (FBG). They are mounted using specially designed and tested holders

for mounting on the brake linkage. They provide quick assembly and the measurement of strain in the

direction parallel to the axis of the linkage. The structure of the holder also allows for the measurement

in 4 positions turned every 90 relative to one another. Such a measurement enables a comprehensive

analysis of strains and stresses in the brake linkage. In the work, it was shown that there is a complex

state of strain and stress in the brake linkage. The previous procedures for linkage testing are inadequate

in relation to this condition. An experimental and numerical method was proposed to assess the state

of linkage stress. It should constitute the basis for the decision of the appraiser to allow the linkage for

further use. The method proposed in the work also allows for continuous measurements of linkage strains

as well as dynamic braking tests.

The technology for gob-side entry retaining in steep coal seams is still in the development stage. The

analysis results of the caving structure of main roof, low influence of gateway’s stability because of long

filling distance and weak dynamic effect of the gateway, and the low stress redistribution environment

indicate that using this technology in steep coal seams has significant advantages. Moreover, to reinforce

the waste rock and the soft floor and to better guard against the impact of the waste rock during natural

filling, a rock blocking device and grouting reinforcement method were invented, and theoretical calculations

result show that the blocking device has high safety factor. In addition, we also developed a set of

hydraulic support devices for use in the strengthening support zone. Furthermore, because the retaining

gateway was a systematic project, the selection of the size and shape of the gateway cross section and its

support method during the initial driving stage is a key step. Thus, first, a section the size of bottom width

and roof height of a new gateway was determined to meet any related requirements. Then, according

to the cross sections of 75 statistical gateways and the support technique, it chosen a trapezoidal cross

section when the dip of the coal seam is 35° < α ≤ 45°, a special and an inclined arch cross section when

45° < α ≤ 55°. Eventually, a support system of bolts and cables combined with steel mesh and steel belts

was provided. The support system used optimized material and improved parameters, can enhanced the

self-bearing ability of the surrounding coal and rock masses.

In the process of coal extraction, a fractured zone is developed in the overburden above the goaf. If

the fractured zone is connected with an aquifer, then water inrush may occur. Hence, research and analysis

of the height of overburden fractured zone (HOFZ) are of considerable significance. This study focuses

on the HOFZ determination in deep coal mining. First, general deformation failure characteristics of

overburden were discussed. Second, a new method, numerical simulation by orthogonal design(NSOD),

have been proposed to determinate the HOFZ in deep coal mining. Third, the validity of NSOD is verified

in the practical application, compared with empiric al formula in Chinese Regulations and in-situ test.

These three methods were applied to determine the HOFZ of working face No. 111303 in No. 5 coal

mine. The pre dicted HOFZ of NSOD is found to be similar to the result of the in-situ test (8.9% relative

error), whereas the HOFZ calculated by the empirical formula has extremely large error (25.7% relative

error). Results show that the NSOD can reliably predict the HOFZ in deep coal mining and reduce time

and expenses required for in-situ test.

The paper presents results of research on cobalt and nickel ions removal from monocomponent solutions

using Purolite ion exchange resins. It has been shown that C 160 ion exchange resin has the best

sorption properties for both ions (Qe – 72.5 mg Co/g and 88.2 mg Ni/g). Regeneration process of this

ion exchanger has high efficiency, achieving about 93% for cobalt ions and about 84% in case of nickel

ions. It has been shown that the use of ion exchange method with suitable ion exchange resins guarantees

effective removal of cobalt and nickel ions from solutions with very high concentrations corresponding

to contents of these metals in industrial wastewaters (e.g. galvanic). In case of C 160 ion exchange resin,

after the sorption process is carried out in one 50 minute cycle, the cobalt concentration decreased from

about 30 000 mg/L to about 9 500 mg/L (approx. 68%), whereas nickel concentration reached about

6 300 mg/L (approx. 79%). Studied chelating resins don’t have such high sorption capacities. In their

case, it is required to convert cobalt and nickel ions into complex forms. The kinetics of studied processes

were described by pseudo-second order equations.

For most precious metal mines, cemented tailings backfill slurry (CTBS) with different cement-sand

ratio and solid concentration are transported into the gobs to keep the stability of the stope and mitigate

environmental pollution by mine tailing. However, transporting several kinds of CTBS through the same

pipeline will increase the risk of pipe plugging. Therefore, the joint impacts of cement-sand ratio and

solid concentration on the rheological characteristics of CTBS need a more in-depth study. Based on the

experiments of physical and mechanical parameters of fresh slurry, the loss of pumping pressure while

transporting CTBS with different cement-sand ratio, flux and solid mass concentration were measured

using pumping looping pipe experiments to investigate the joint impacts of cement-sand ratio and solid

concentration on the rheological characteristics of CTBS. Meanwhile, the effect of different stopped pumping

time on blockage accident was revealed and discussed by the restarting pumping experiments. Furthermore,

Fluent software was applied to calculate the pressure loss and velocity distribution in the pipeline to further

analysis experimental results. The overall trends of the simulation results were good agreement with the

experiment results. Then, the numerical model of the pipeline in the Sanshandao gold mine was conducted

to simulate the characteristics of CTBS pipeline transportation. The results show that the pumping pressure

of the delivery pump can meet the transportation requirements when there is no blockage accident. This

can provide a theoretical method for the parameters optimizing in the pipeline transportation system.

This article presents the use of a multi-criterion Analytic Hierarchy Process (AHP) method to assess

geological and mining condition nuisance in longwall mining operations in selected coal mines in Poland.

For this purpose, a methodology has been developed which was used to calculate the operational nuisance

indicator (WUe) in relation to the cost of mining coal in individual longwalls. Components of the aggregate

operational nuisance indicator include four sub-indicators: the natural hazards indicator (UZN), an

indicator describing the seam parameters (UPZ), an indicator describing the technical parameters (UT)

and an environmental impact indicator (UŚ). In total, the impact of 28 different criteria, which formed

particular components of the nuisance indicators were analysed. In total 471 longwalls in 11 coal mines

were analysed, including 277 longwalls that were mined in the period of 2011 to 2016 and 194 longwalls

scheduled for exploitation in the years 2017 to 2021.

Correlation analysis was used to evaluate the relationships between nuisance and the operating costs

of longwalls. The analysis revealed a strong correlation between the level of nuisance and the operating

costs of the longwalls under study. The design of the longwall schedule should therefore also take into

account the nuisance arising from the geological and mining conditions of the operations. Selective

operations management allows for the optimization of costs for mining in underground mines using the

longwall system. This knowledge can also be used to reduce the total operating costs of mines as a result

of abandoning the mining operations in entire longwalls or portions of longwalls that may be permanently

unprofitable. Currently, underground mines do not employ this optimization method, which even more

emphasizes the need for popularizing this approach.

Recalling the body of experience gathered in the collieries of the Upper Silesian Coal Basin, the

increased risk of seismicity and rockburst occurrences in confined conditions including the exploitation of

remnants were identified. This study investigates geomechanical aspects of longwall mining in the areas

affected by old excavations aimed at relaxation of a multi-bed deposits within a thick coal seam or a group

of seams. It is assumed that high-energy seismicity is another factor determining the rockburst hazard

alongside the state of stress. A case study is recalled, describing a colliery where mining-induced seismic

activity of a de-stressed coal seam remained at the level comparable to or higher than it was experienced

in the de-stressed seam operations. An analytical model was used to study the stress state and potential

loss of structural continuity of an undisturbed rock body surrounding the longwall panel being mined

beneath or over the abandoned workings. Recalling the developed model of the system involving nonlinear

functions demonstrating the existence of abandoned mine workings within the rock strata, computer

simulations were performed to evaluate the rockburst hazards along the face area. Discussions of results

are based on observations of immediate roof convergence and the vertical stress concentration factor at

the longwall face zone. Computational data of the modelled mining situations demonstrates that despite

using the de-stressing method of mining, the occurrence of events impacting on mine working beneath

and over abandoned workings cannot be precluded. Here the scale of rockburst hazards is determined by

local mining and geological conditions, such as the type and extent of abandoned workings, their age and

vertical distance between them and the coal seam currently mined.

Households are the most significant group of consumers in the municipal and household sector in

Poland. In 2010-2016, households consumed annually from 8.9 to 10.8 million Mg of coal (77-81%

share in this sector).

As of the beginning of 2018, seven voivodships in Poland have already introduced anti-smog resolutions,

one has its draft, three are considering introduction of such resolutions. In the face of introducing

anti-smog resolutions, the analysis of coal consumption by households was conducted for a situation

where anti-smog resolutions will be introduced in all voivodships in Poland.

A forecast of hard coal consumption by Polish households in 2017-2030 was presented in the article.

Two scenarios differentiated in terms of calorific value of coal were taken into account: (i) concerned coal

with a calorific value of 24 MJ/kg (min. Q for eco-pea coal: grain size 5.0-31.5 mm), (ii) – coals with

a calorific value of 26 MJ/kg (Q recommended for use by producers of class 5 boilers).

In the perspective of 2030, the largest decrease in hard coal consumption can be expected (jointly)

in the voivodships of Śląskie, Dolnośląskie, Opolskie and Lubuskie. Under the assumptions made, in

relation to 2016, it may be reduced by half and fall from 2.8 to the level of 1.4-1.5 million Mg. The

smallest decreases in consumption may occur (jointly) in the Małopolskie, Lubelskie, Podkarpackie and

Świętokrzyskie voivodships – decrease by 16-22% and fall from 2.6 to approximately 1.9-2.0 million Mg.

On a national scale, coal consumption may decrease from the current 10.4 (2016) to around 6.3-6.8 million

Mg (a decrease of 30-35%).

Despite the decrease in hard coal consumption in the 2030 perspective, one should expect an increase

in demand for high quality coal dedicated to modern boilers (usually pea assortments) as well as qualified

coal fuels (mainly eco-pea coal).

Explosions of coal dust are a major safety concern within the coal mining industry. The explosion and

subsequent fires caused by coal dust can result in significant property damage, loss of life in underground

coal mines and damage to coal processing facilities. The United States Bureau of Mines conducted

research on coal dust explosions until 1996 when it was dissolved. In the following years, the American

Society for Testing and Materials (ASTM) developed a test standard, ASTM E1226, to provide a standard

test method characterizing the “explosibility” of particulate solids of combustible materials suspended

in air. The research presented herein investigates the explosive characteristic of Pulverized Pittsburgh

Coal dust using the ASTM E1226-12 test standard. The explosibility characteristics include: maximum

explosion pressure, (Pmax); maximum rate of pressure rise, (dP/dt)max; and explosibility index, (Kst). Nine

Pulverized Pittsburgh Coal dust concentrations, ranging from 30 to 1,500 g/m3, were tested in a 20-Liter

Siwek Sphere. The newly recorded dust explosibility characteristics are then compared to explosibility

characteristics published by the Bureau of Mines in their 20 liter vessel and procedure predating ASTM

E1126-12. The information presented in this paper will allow for structures and devices to be built to

protect people from the effects of coal dust explosions.

The evaluation of threats connected with the presence of methane in coal seams is based on our

knowledge of the total content of this gas in coal. The most important parameter determining the potential

of coal seams to accumulate methane is the sorption capacity of coal a. It is heavily influenced by the

degree of coalification of the coal substance, determined by the vitrinite reflectance R0 or the content of

volatile matter V daf. The relationship between the degree of coalification and the sorption capacity in the

area of the Upper Silesian Coal Basin (USCB) has not been thoroughly investigated, which is due to the

zonation of methane accumulation in this area and the considerable changeability of methane content in

various localities of the Basin. Understanding this relationship call for in-depth investigation, especially

since it depends on the analyzed reflectance range. The present work attempts to explain the reasons for

which the sorption capacity changes along with the degree of coalification in the area of Jastrzębie (the

Zofiówka Monocline). The relationship between parameters R0 and V daf was investigated. The authors

also analyzed changes of the maceral composition, real density and the micropore volume. Furthermore,

coalification-dependent changes in the sorption capacity of the investigated coal seams were identified.

The conducted analyses have indicated a significant role of petrographic factors in relation to the accumulation

properties of the seams located in the investigated area of USCB.

The coal exploitation in the Upper Silesia region (along the Vistula River) triggers the strata seismic

activity, characterized by very high energy, which can create mining damage of the surface objects, without

any noticeable damages in the underground mining structures. It is assumed that the appearance of the

high energy seismic events is the result of faults’ activation in the vicinity of the mining excavation. This

paper presents the analysis of a case study of one coal mine, where during exploitation of the longwall

panel no. 729, the high energy seismic events occurred in the faulty neighborhood. The authors had analyzed

the cause of the presented seismic events, described the methods of energy decreasing and applied

methods of prevention in the selected mining region. The analysis concluded that the cause of the high

energy seismic events, during the exploitation of the longwall panel no. 729 was the rapid displacements

on the fault surface. The fault’s movements arose in the overburden, about 250 m above the excavated

longwall panel, and they were strictly connected to the cracking of the thick sandstone layer.

Geodesic measurements of mining area deformations indicate that their description fails to be regular,

as opposed to what the predictions based on the relationships of the geometric-integral theory suggest.

The Knothe theory, most commonly applied in that case, considers such parameters as the exploitation

coefficient a and the angle of the main influences range tgβ, describing the geomechanical properties of the

medium, as well as the mining conditions. The study shows that the values of the parameters a = 0.8 and

tgβ = 2.0, most commonly adopted for the prediction of surface deformation, are not entirely adequate in

describing each and every mining situation in the analysed rock mass. Therefore, the paper aims to propose

methodology for determining the value of exploitation coefficient a, which allows to predict the values

of surface subsidence caused by underground coal mining with roof caving, depending on geological and

mining conditions. The characteristics of the analysed areas show that the following factors affect surface

subsidence: thickness of overburden, type of overburden strata, type of Carboniferous strata, rock mass

disturbance and depth of exploitation. These factors may allow to determine the exploitation coefficient a,

used in the Knothe theory for surface deformation prediction.

One of the main purpose of accurate blasting in open pit mining is to achieve optimum rock fragmentation.

The degree of rock fragmentation plays a significant role in order to control and minimise the

overall production cost including loading, hauling and crushing. In the present paper, the application of

a Number-Size (N-S) fractal model is intended to classify the blast fragmentation size in the Jalal-Abad

iron mine, SW Iran, using GoldSize image analysis software for four blasting with the obtained result

being compared with Kuz-Ram curves. To do this, the fractal dimensions via N-S log-log plots were

generated based on the output of the GoldSize software. The results indicated that the fragmented rocks

have a multifractal nature with four/five different fragmented populations in terms of size namely; the fine

rocks with the size of less than 16 cm, Mean-fragment values between 16 and 45 cm, In-range between

45 and 70 cm and finally, oversize larger than 70 cm.