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Use of machine learning algorithms to assess the state of rockburst hazard in underground coal mine openings

Journal of Rock Mechanics and Geotechnical Engineering 2022年第3期14卷 703-713页

作者： lukasz wojtecki Sebastian Iwaszenko Derek B.Apel Mirosawa Bukowska Janusz Makówka Central Mining Institute Katowice40-166Poland School of Mining and Petroleum Engineering University of AlbertaEdmontonT6G 2R3Canada

The risk of rockbursts is one of the main threats in hard coal mines. Compared to other underground mines, the number of factors contributing to the rockburst at underground coal mines is much *** such as the coal seam tendency to rockbursts, the thickness of the coal seam, and the stress level in the seam have to be considered, but also the entire coal seam-surrounding rock system has to be evaluated when trying to predict the rockbursts. However, in hard coal mines, there are stroke or stress-stroke rockbursts in which the fracture of a thick layer of sandstone plays an essential role in predicting rockbursts. The occurrence of rockbursts in coal mines is complex, and their prediction is even more difficult than in other mines. In recent years, the interest in machine learning algorithms for solving complex nonlinear problems has increased, which also applies to geosciences. This study attempts to use machine learning algorithms, i.e. neural network, decision tree, random forest, gradient boosting, and extreme gradient boosting(XGB), to assess the rockburst hazard of an active hard coal mine in the Upper Silesian Coal Basin. The rock mass bursting tendency index WTGthat describes the tendency of the seam-surrounding rock system to rockbursts and the anomaly of the vertical stress component were applied for this purpose. Especially, the decision tree and neural network models were proved to be effective in correctly distinguishing rockbursts from tremors, after which the excavation was not damaged. On average, these models correctly classified about 80% of the rockbursts in the testing datasets.

关键词： Hard coal mining Rockburst hazard Machine learning algorithms

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The influence of mining factors on seismic activity during longwall mining of a coal seam

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International Journal of Mining Science and Technology 2021年第3期31卷 429-437页

作者： Łukasz wojtecki Joanna Kurzeja Małgorzata Knopik Department of Geology and Geophysics Central Mining Institute40-166 KatowicePoland Polish Mining Group 40-039 KatowicePoland

In this article an attempt to determine the influence of mining factors on the seismic activity during the longwall mining of the upper layer of coal seam no.405/2 in one of the Polish hard coal mines in the Upper Silesian Coal Basin was *** longwall panels were mined in analogous geological conditions and based on the same mining system and ***,there was significant difference with regards to the mining factors,which was reflected in the observed seismic *** tools used in mining seismology were applied to illustrate the aforementioned influence of mining factors,*** frequency-energy distribution,the frequency-magnitude distribution,the 2 D distribution of released seismic energy,the relationship between released seismic energy and the volume of mined coal,the Benioff strain release,and the Gutenberg-Richter(GR)b coefficient distribution(b is the proportion between high and low energy tremors).Concerning the Benioff strain release,a new solution,based on the slope of a fitted line in a moving time window,is proposed.

关键词： Underground coal mining Induced seismicity Seismic statistics Benioff strain release

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Spatiotemporal analysis of elastic and inelastic deformations in roof-rocks from seismological observations

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International Journal of Mining Science and Technology 2021年第2期31卷 241-251页

作者： Maciej JMendecki RafałPakosz Łukasz wojtecki Wacław MZuberek Faculty of Environmental Sciences the University of Silesia in Katowice41-200 SosnowiecPoland Polish Mining Group 40-039 KatowicePoland Central Mining Institute 40-166 KatowicePoland

The spatiotemporal analysis of seismic zones characterised by the scattering and accumulation of strain energy in the roof-rocks of the excavated longwall panel where inelastic or elastic deformations occurred during hard coal seam mining is *** studied longwall panel was designed to utilize the effect of partial stress relaxation caused by the earlier extraction of the coal seams located above.A full seismic moment tensor and spectral source parameter analyses were used to obtain information about the degree of inelastic and elastic coseismic *** study also showed that these deformation changes correspond to variation in the Benioff strain release ***,analyses of deformation zones were compared with the relationship between radiated energy and the excavated volume of rocks per *** concept of balanced seismic energy release assumed the exponential increase of released seismic energy with the increase in the volume of excavated *** between the observed and predicted radiated energies indicated that strain energy in selected zones in the rock mass was either scattered if the prediction was overestimated,or accumulated if ***,the study showed that elastic deformation in one zone can lead to inelastic deformation in the same zone.

关键词： Mining seismicity Seismic source volume Apparent volume Hard coal mine Longwall mining Benioff strain

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Effects of torpedo blasting on rockburst prevention during deep coal seam mining in the Upper Silesian Coal Basin

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第4期9卷 694-701页

作者： L. wojtecki P. Konicek J. Schreiber Polish Mining Group Powstanców 30 Katowice 40-039 Poland Department of Geomechanics and Mining Research Institute of Geonics Czech Academy of Sciences Studentska 1768 Ostrava-Poruba 708 00 Czech Republic

In the Upper Silesian Coal Basin(USCB),coal seams are exploited under progressively more difficult geological and mining conditions(greater depth,higher horizontal stress,more frequent occurrence of competent rock layers,etc.).Mining depth,dislocations and mining remnants in coal seams are the most important factors responsible for the occurrence of rockburst *** mining next to the mining edges of neighbouring coal seams is particularly *** levels of rockburst hazards are minimised via the use of rockburst prevention *** active prevention method is torpedo blasting in roof *** blastings are performed in order to decrease local stress concentrations in rock masses and to fracture the roof rocks to prevent or minimise the impact of high-energy tremors on *** estimation of the effectiveness of torpedo blasting is particularly important when mining is under difficult geological and mining *** blasting is the main form of active rockburst prevention in the assigned colliery in the Polish part of the *** effectiveness of blasting can be estimated using the seismic effect method,in which the seismic monitoring data and the mass of explosives are taken into *** seismic effect method was developed in the Czech Republic and is always being used in collieries in the Czech part of the coal ***,this method has been widely adopted for our selected colliery in the Polish part of the coal *** effectiveness of torpedo blastings in the faces and galleries of the assigned longwall in coal seam 506 has been *** results show that the effectiveness of torpedo blastings for this longwall was significant in light of the seismic effect method,which corresponds to the in situ *** seismic effect method is regularly applied to estimating the blasting effectiveness in the selected colliery.

关键词： Rockburst prevention Torpedo blasting Seismic effect Upper Silesian Coal Basin(USCB)

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A criterion for high-cycle fatigue life and fatigue limit prediction in biaxial loading conditions

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Acta Mechanica Sinica 2016年第4期32卷 696-709页

作者： lukasz Pejkowski Dariusz skibicki Faculty of Mechanical Engineering University of Science and Technology KaJiskiego 7 85-789 Bydgoszcz Poland

This paper presents a criterion for high-cycle fatigue life and fatigue strength estimation under periodic proportional and non-proportional cyclic loading. The criterion is based on the mean and maximum values of the second invariant of the stress deviator. Important elements of the criterion are： function of the non-proportionality of fatigue loading and the materials parameter that expresses the materials sensitivity to non-proportional loading. The methods for the materials parameters determination uses three S–N curves： tension–compression, torsion, and any non-proportional loading proposed. The criterion has been verified using experimental data, and the results are included in the paper. These results should be considered as promising. The paper also includes a proposal for multiaxial fatigue models classification due to the approach for the nonproportionality of loading.

关键词： criterion fatigue proportional invariant verified coordinates scatter cycle steels assumed

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Life cycle assessment of opencast lignite mining

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International Journal of Coal Science & Technology 2021年第6期8卷 1272-1287页

作者： lukasz Lelek Joanna Kulczycka Mineral and Energy Economy Research Institute Polish Academy of SciencesWybickiego 7A Str.31-261 CracowPoland Faculty of Management AGH University of Science and Technology30-067 CracowPoland

The life cycle phase of fossil fuel extraction is mainly considered in the life cycle assessment(LCA)when evaluating the energy production *** is then only one of many unit processes,which contribute to the blurring of mining-relevant *** are few items in the literature focusing exclusively on the lignite mining phase and analysing the specific mining conditions and associated environmental *** article focuses on the LCA of lignite mining processes on the basis of data coming from a Polish *** technology for opencast lignite mining is noted for its high production efficiency,high level of recovery and lower risk as regards the safety of workers when compared with underground mining ***,the need to remove large amounts of overburden to uncover the deposit contributes to a much greater degradation of the *** the results obtained,several key(hot spot)elements of the lignite mining operations were distinguished for modelling the environmental impact,i.e.:calorific value,the amount of electricity consumption,the manner in which waste and overburden are *** a result there is a high sensitivity of the final indicator to changes in these impacts.

关键词： Life cycle assessment(LCA) Lignite Mining Fossil fuel

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Grobner-Shirshov Bases for Plactic Algebras

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Algebra Colloquium 2014年第4期21卷 591-596页

作者： lukasz Kubat Jan Oknifiski Institute of Mathematics Polish Academy of Sciences Sniadeckich 8 00-956 Warsaw Poland Institute of Mathematics Warsaw University Banacha 2 02-097 Warsaw Poland

A finite GrSbner-Shirshov basis is constructed for the plactic algebra of rank 3 over a field K. It is also shown that plactic algebras of rank exceeding 3 do not have finite GrSbner-Shirshov bases associated to the natural degree-lexicographic ordering on the corresponding free algebra. The latter is in contrast with the case of a strongly related class of algebras, called Chinese algebras.

关键词： plactic monoid GrSbner-Shirshov basis semigroup algebra

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Relaxation dynamics of excited states of Tm3+ ions in TeO2-ZnO-Na2O-Y2O3 glasses

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Journal of Rare Earths 2019年第11期37卷 1188-1195页

作者： lukasz Marek Marcin Sobczyk Wladyslaw Wrzeszcz Faculty of Chemistry University of Wroclaw

Tellurite glasses with the composition of xTm2O3-(6-x)Y2O3-3Na2O-25ZnO-66TeO2(where 0≤x≤6)were obtained by the melt-quenching ***(300 K),excitation(300 K)and fluorescence spectra(300 K)as well as fluorescence decay curves of Tm^3+-doped title glasses are presented and discussed in *** Judd-Ofelt analysis based on the room temperature absorption spectrum was applied for determination of fundamental fluorescence properties such as radiative transition probabilities(AT),branching ratios(βR),radiative lifetimes(τR)of the emitting levels of the Tm^3+ion and stimulated emission cross-sections(σem).Fluorescence spectra were recorded and analysed in the visible and near-infrared spectral *** emission and effective cross-section were calculated for the 3F4→3H6 transition,showing that the investigated glasses are promising laser host materials,operating at 1.8μ*** observed concentration quenching and non-exponential decay curves from the 1 G4 and 3H4 states indicate nonradiative energy transfer between Tm^3+*** analysis of non-exponential fluorescence decay curves from the 1 G4 and 3H4 levels was carried out in framework of the InokutiHirayama and Yokota-Tanimoto models and energy transfer microparameters were *** self-quenching model was proposed for describing relaxation of the first excited state of the Tm^3+ion.

关键词： Tm3+ Tellurite glasses Judd-Ofelt theory Luminescence Laser materials Non-radiative energy transfer

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Laser-induced white-light emission from graphene ceramics–opening a band gap in graphene

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Light(Science & Applications) 2015年第1期4卷 545-552页

作者： Wieslaw Strek Bartlomiej Cichy lukasz Radosinski Pawel Gluchowski lukasz Marciniak Mikolaj lukaszewicz Dariusz Hreniak Polish Academy of Sciences Institute of Low Temperatures and Structural Research50-422 WroclawPoland Wroclaw University of Technology Group of Chemical and Biochemical Processes50-370 WroclawPoland

Recent theoretical and experimental studies have indicated the existence of a new stable phase of carbon with mixed sp^(2) and sp^(3) hybridized bonds—*** a two-layered structure with sp^(2)/sp^(3) bonds may be observed after the photostimulation of highly oriented pyrolytic graphene with femtosecond laser *** hidden multistability of graphene may be used to create a semiconducting phase immersed in the semimetallic continuum,resulting in bandgap *** demonstrate that bandgap opening and light emission from graphene is possible using continuous-wave laser beams with wavelengths from the visible(405 nm)to the near-infrared range(975 nm).We demonstrate that without the application of cooling,the effective temperature of the emitting sample remains lower than 900 K,which is far below the value predicted by the theory of black-body ***,light emission from a graphene sample may be observed at temperatures as low as 10 K.

关键词： ceramics graphene photoluminescence white light

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Substructure isolation and damage identification using free responses

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Science China(Technological Sciences) 2014年第9期57卷 1698-1706页

作者： HOU JiLin JANKOWSKI lukasz OU JinPing School of Civil Engineering Dalian University of Technology Smart-Tech Centre Institute of Fundamental Technological Research Polish Academy of Sciences School of Civil Engineering Harbin Institute of Technology

Structural health monitoring （SHM） has become a hot and intensively researched field in civil engineering. Thereinto, damage identification play an important role in maintaining structural integrity and safety. Many effective methods have been proposed for damage identification. However, accurate global identification of large real-world structures is not easy due to their com- plex and often unknown boundary conditions, nonlinear components, insensitivity of glohal response to localized damages, etc. Furthermore, global identification often requires lots of sensors and involves large number of unknowns. This is costly, rarely feasible in practice, and usually yields severely ill-conditioned identification problems. Substructuring approach is a possible solution： substructuring methods can focus on local small substructures; they need only a few sensors placed on the substruc- ture and yield smaller and numerically much more feasible identification problems. This paper proposed an improved sub- structure method using local free response for substructure damage identification. The virtual supports are constructed by Sub- structure Isolation Method （SIM） using the linear combination of the substructural responses. The influence of the global errors is isolated by adding the virtual supports on the main degree of freedoms （DOFs） of the substructure. Through the correlation analysis, the substructural modes are selected and used for damage identification of the substructure. A plain model of cable stayed bridge is used for the verification of the proposed method.

关键词： structural health monitoring (SHM) damage identification substructure cable stayed bridge free response

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