Accurate understanding of the three-dimensional (3d) morphology of a complex goaf and its relative displacement in space is a precondition to further analyzing the stability of the cavity. in this study, to make an accurate stability analysis of the goaf, laser detection and numerical simulation are used to study the interior space form of goaf and the change characteristics of stress and displacement in goaf. The results of the study show that the BLSS-PE mining 3d laser system as a field detection tool can detect the morphology of the cavity more comprehensively and improve the accuracy of the detection data to a certain extent. Combined with the numerical simulation software analysis, it can be seen that the maximum principal stress in the 818-2# goaf increases after excavation. in addition, the maximum value appears in the top and bottom plates of the goaf, and the minimum stress remains nearly unchanged. The tensile stress appears in the upper and lower plates but is lower than the surrounding rock. The maximum horizontal and vertical displacements of the 818-2# goaf are small. The plastic zone appears in the surrounding rock of the goaf as the mining work progresses, but the area is small. it is concluded that the goaf is relatively stable overall. The research results may provide a strong reference for ground pressure management in mines and comprehensive control of goaves.

For the prevention and control of rockburst in underground coal mines, a detailed assessment of a rockburst hazard area is crucial. in this study, the dependence between stress and elastic wave velocity of axially-loaded coal and rock samples was tested in a laboratory. The results show that P-wave velocity in coal and rock is positively related to axial stress and can be expressed by a power function. The relationship showed that high stress and a potential rockburst area in coal mines can be determined by the elastic wave velocity anomaly assessment with passive seismic velocity tomography. The principle and implementation procedure of passive seismic velocity tomography for elastic wave velocity were introduced, and the assessment model of rockburst hazard using elastic wave velocity anomaly was built. A case study of a deep longwall panel affected by rockbursts was introduced to demonstrate the effectiveness of tomography. The rockburst prediction results by passive velocity tomography closely match the dynamic phenomenon in the field, which indicates the feasibility of elastic wave velocity anomaly for rockburst hazard prediction in coal mines.

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In the longwall exploitation system, the main gates are subject of the most intensive movements of the rock mass, where the proximity of the excavation front is a key factor. The paper presents the results of a research on the constants mb and s of Hoek-Brown failure criterion for the rocks surrounding the gallery: shale, sandy shale, coal and medium-grained sandstone, in relation to the distance to longwall face. The research comprised numerical modeling based on convergence monitoring records. The convergence measurements were carried out on three stations in a selected maingate in a coal mine from Upper Silesia Coal Basin near Jastrzębie-Zdrój, concurrently with changing distance to the longwall face. The measured were the width, the height and the heave of the floor of the gate. The measurements showed that the convergence at the longwall-maingate crossing was 1.5-3 times greater than in the locations much further from the longwall face. It was demonstrated that this effect was due to continuously changing properties of the rock-mass surrounding the gallery that can be expressed as decreasing empirical parameters mb i s of Hoek-Brown's criterion. These parameters are decreasing exponentially together with the distance to the longwall face The consistency between the theoretical and factual curve varies between 70% to 98%. The change of each of the parameters can be described by general equation P = a • exp (-b • d ), where a, b are constants, and d is the distance to the excavation face. The authors highlight that during the measurements period the horizontal stress was 1.45 to 1.61 times greater than the concurrent vertical stress. The so high horizontal stress causes heave of unsupported gallery floor which is commonly observed in the mines in Silesia.

The paper presents a new method for measuring the strain and load of wire ropes guide using fiber optic sensors with Bragg gratings. Its principle consists in simultaneous fiber optic measurement of longitudinal strain of the rope and transverse strain of the bolt fixing the rope. The tensometric force transducers which have been used so far were only able to determine the load in the head securing the rope through an indirect measurement using a special strain insert. They required calibration, compensation of temperature changes, as well as periodic checking and calibration. The head fastening the rope required significant design changes. Measurement based on fiber optic sensors does not have these drawbacks and is characterized by a much higher accuracy and safety of measurements, because the working medium is light. The fastening head does not change. The measurement of the rope load may be based on the change of strain value or indirectly by means of measuring the deflection of the bolt fixing the rope holder. The proposed solution consists in placing the optical fiber with Bragg grating inside the bolt. It enables continuous measurements with a frequency of 2 kHz. A special test bench was built at the Research and Supervisory Centre of Underground Mining. Testing on guide ropes was carried out in a mining hoist in the Piast mine.

The correct management of underground works, petroleum and gas reservoirs and geothermal applications relies on the hydromechanical behaviour of rock masses. We describe a laboratory approach to measuring permeability for different types of rock specimens. A laboratory system was designed and set up using rock mechanics equipment (a servo-controlled hydraulic press, a Hoek cell, a pump for injecting water and a scale for measuring the volume of water flow). To verify the validity of the permeability measurements, tests were carried out on a reference porous rock (Corvio sandstone), with results showing good agreement with those published in the literature. Tests were subsequently carried out on artificially fissured granite specimens with different joint patterns, submitted to various confinement stresses up to 20 MPa. Results showed good agreement with traditional Klinkenberg test results. Other tests done with artificially fissured specimens are described for demonstrative purposes.

MeasureMents of the Methane ConCentration along the longwall exCavations and longwallone of the most hazardous places in mines are longwall areas.they emit a considerable amount of methane to the ventilation air. the emission depends on many but mostly known factors.the article presents the research results on changes in the methane concentration along the longwall excavations and longwall.the distributions were obtained based on a measurement experiment at the Zg Brzeszcze mine in Poland.the author's research aimed to experimentally determine the concentration of methane as a function of the length of excavation for the longwall excavations and longwall.As a result, methane concentration trends along the excavations were obtained.the conclusions show the pros and cons of the method used, and it allows to set the right direction in the development of measurement systems and sensors.

The ConCenTraTion of rare earTh elemenTs in The Polish Power PlanT wasTes the article presents the results of laboratory tests determining the concentration of rare earth elements (Ree) in coal-burning wastes to assess their economic usefulness. the content of valuable elements was determined by the technique of inductively coupled plasma mass spectrometry (icP-Ms) in the material collected from three regions of southern Poland. a mixture of waste (including fly ash, furnace slag) from heat and power plants using coal for thermal transformation processes was an object for testing. Part of the research project was to identify a share of the rare elements in the collected samples with a selected grain class of <0.045 mm.

The underground complicated testing environment and the fan operation instability cause large random errors and outliers of the wind speed signals.The outliers and large random errors result in distortion of mine wind speed monitoring, which possesses safety hazards in mine ventilation system.Application of Kalman filter in velocity monitoring can improve the accuracy of velocity measurement and eliminate the outliers.Adaptive Kalman Filter was built by automatically adjusting process noise covariance and measurement noise covariance depending on the differences between measured and expected speed signals.We analyzed the fluctuation of airflow flow using data of wind speed flow and distribution characteristics of the tunnel obtained by the Laser Doppler Velocimetry system (LDV) studies.A state-space model was built based on the tunnel airflow fluctuations and wind speed signal distribution.The ad aptive Kalman Filter was calculated according to the actual measurement data and the Expectation Maximization (EM) algorithm.The adaptive Kalman filter was used to shield fluid pulsation while preserving system-induced fluctuations.Using the Kalman filter to treat offline wind speed signal acquired by LDV, the reliability of Kalman filter wind speed state model and the characteristics of adaptive Kalman Filter were investigated.Result s showed that the adaptive Kalman filter effectively eliminated the outliers and reduced the rootmean-squares error (RMSE), and the adaptive Kalman filter had better performance than the traditional Kalman filter in eliminating outliers and reducing RMSE.Field experiments in online wind speed monitoring were conducted using the optimized adaptive Kalman Filter.Results showed that adaptive Kalman filter treatment could monitor the wind speed with smaller RMSE compared with LVD monitor.The st udy data demonstrated that the adaptive Kalman filter is reliable and suitable for online signal processing of mine wind speed monitor.

This paper shows the possibility that the mineral coal existing in the mining basins of northern Spain have a high added value. This would facilitate its future use in different fields such as new materials, nanotechnology, energy use in situ, coal bed methane, enhanced coal bed methane and coalmine methane. An analytical study of mineral coal samples is carried out. The samples come from two deposits located in coal basins of the Cantabrian Mountains. The duly prepared samples are subjected to an activation process. Within this transformation, different treatments are applied to different sub-samples. Some of the sub-samples suffer a previous demineralization by successive attacks with acids, followed by oxidation and pyrolysis. Finally, all of them are activated with CO 2 and H 2 O (steam) . The carbonaceous products resulting from each treatment are characterised. The results show that all the pre-treatments used were positive for the textural development of the materials. Likewise, proper management of the processes and of the different operating variables allows the procurement of carbonaceous materials with a "tailor-made" structural development of the coal type. This material receives the name "activated" and can be employed in specific processes.