Underground Conditions Research Articles

Well logs reconstruction of petroleum energy exploration based on bidirectional Long Short-term memory networks with a PSO optimization algorithm

During petroleum energy exploration, estimating missing well logs from existing logging data is very meaningful. Due to a highly nonlinear relationship between various logging data and a challenge to express the complexity of underground geological conditions by deterministic functions, traditional methods are difficult to meet the need of accurate interpretations of log data and fine descriptions of reservoirs. Nevertheless, deep learning method provides an advanced means for reconstructing well logs, and can directly map existing logging data to missing well logs. In this paper, we adopt the PSO-BiLSTM network that combines the BiLSTM (Bidirectional Long Short-term Memory) network with the PSO (Particle Swarm Optimization) algorithm. BiLSTM is an excellent data-driven method that can extract bidirectional temporal well logging data. PSO algorithm enhances the performance of BiLSTM model in predicting missing well logs through hyperparameter optimization, global search capability, and adaptive learning. At the same time, RMSE, MAE, and MAPE are used as indicators to evaluate the performance of PSO-BiLSTM model. The results show that when a PSO-BiLSTM model is applied to well logs reconstruction experiments, the reconstructed value of a log curve is in good agreement with its real value. Compared to LSTM and BiLSTM models, a PSO-BiLSTM model provides the best accuracy and stability in predicting missing well logs. The PSO-BiLSTM model strengthens the extraction of relevant logging information and reduces the error of parameter adjustment. It has an important reference significance for the reconstruction of well logs in complex formations.

Analysis of Soil Slope Stability under Underground Coal Seam Mining Using Improved Radial Movement Optimization with Lévy Flight

Underground coal seam mining significantly reduces the stability of slopes, especially soil slopes, and an accurate evaluation of the stability of soil slopes under underground mining conditions is crucial for mining safety. In this study, the impact of coal seam mining is considered as the additional horizontal and vertical stresses acting on the slope, and an equation for calculating the safety factor of soil slopes under underground mining conditions is derived based on the rigorous Janbu method. Then, the Improved Radial Movement Optimization (IRMO) algorithm is introduced and combined with Lévy flight optimization to conduct global optimization searches, obtaining the critical sliding surface and corresponding safety factor of the soil slope under underground coal seam mining. Through comparisons with the numerical simulation results in three different case studies, the feasibility of applying the IRMO algorithm with Lévy flight to analyze the stability of soil slopes under underground mining is demonstrated. This ensures the accuracy and stability of the calculation results while maintaining a high convergence efficiency. Furthermore, the effects of the mining thickness and mining direction on slope stability are analyzed, and the results indicate that a smaller mining thickness and mining along the slope are advantageous for slope stability. The method proposed in this study provides valuable insights for preventing the slope instability hazards caused by underground coal seam mining.

Experimental Study on the Gelling Properties of Nano-Silica Sol and Its Spontaneous Imbibition Grouting Mudstone

The low-permeability argillaceous rock mass is an unfavorable geological body commonly found in the construction process of underground engineering conditions such as roadways and tunnels. Due to the compact structure and low permeability of the rock mass, grouting with conventional materials cannot effectively seal the micro-cracks of the rock mass. Based on the low efficiency of high-pressure grouting of nano-silica sol, this paper preliminarily explores the regularities and mechanism of grouting and pore sealing of low-permeability rock mass under the action of silica sol imbibition from the aspects of gelling properties of silica sol, core pore structure, imbibition law, and pore sealing characteristics. The results show the following: (1) The increase in particle size during the gel process reduced the injectability and wettability of the silica sol. The imbibition properties of silica sol were time-varying, and the deterioration inflection points of injectability and wettability appeared at 10 h and 9 h, respectively. (2) Catalyst, temperature, gel process, and rock mass permeability will affect the law of core imbibition, and the injectability and capillary force of the grouting material and rock mass will jointly affect the imbibition process of silica sol. (3) Silica sol imbibition changed the pore size distribution of the core, the pore volume above 50 nm decreased, and the pore volume below 50 nm increased. Silica sol has multiple effects such as filling, adsorption, and percolation in the imbibition process of the micro-pores of rock mass, and the adsorption and percolation of silica are related to the nano micro-pores.

Unveiling Subsurface Characteristics of Cliff Land in Sibang, Bali Through Geoelectric Investigation

The unique geological formations and environmental dynamics of cliffs underscore the significance of comprehending soil composition and structural integrity for diverse applications, such as infrastructure development and environmental conservation. Geoelectrical needs to be done because the underground geological conditions of the cliff must be researched and assessed first before construction is carried out so that construction failure does not occur. This research aims to reveal the subsurface characteristics of cliff soil in Sibang, Bali through geoelectrical investigation. This research was conducted by evaluating the soil condition in the field using the geoelectric resistivity method to the ability of a material to inhibit the flow of electric current and geological regional theories. At points BL-01 and BL-04, there is a significant potential risk of landslides due to the thick layer of breccia, especially during high rainfall or additional loads in the area. Point BL-02 also has a potential risk of landslides due to the thick layer of basalt and wet sand. Meanwhile, points BL-03 and BL-05 are more ideal locations for construction because they consist of relatively stable hard rock. Point BL-06 outside the development zone has layers of gravel, weathered tuffa and andesite which could be considered for future development. Thus, a deep understanding of the geological characteristics of each point is important to manage risks and ensure the safety and sustainability of construction projects in that area.

Solubility of H2-CH4 mixtures in brine at underground hydrogen storage thermodynamic conditions

Concerning the emerging power-to-gas technologies, which are considered the most promising technology for seasonal renewable energy storage, Underground Hydrogen Storage (UHS) has gained attention in the last few years. For safe and efficient storage, possible hydrogen losses due to dissolution into the aquifer must be estimated accurately. Due to safety concerns, experimental measurements of hydrogen solubility in brine at reservoir conditions are limited. In this study, a PVT cell is used to characterize the solubility of hydrogen and its mixtures with methane in saline water/brine. The experiments were carried out at 45, 50, and 55°C and from 1 bar up to 500 bar, mimicking a significant range of possible reservoir conditions. Two brine samples representative of two different reservoirs were tested. Two mixtures of methane and hydrogen (10 mol% H2 and 50 mol% H2, respectively) were considered, along with pure hydrogen, to account for the presence of methane in the primary phase of hydrogen storage in a depleted gas reservoir. In the current paper, a comparison of the experimental results with literature models is provided. At the experiment conditions, the impact of the differences in the composition of the two analyzed brines as well as the impact of the analyzed range of temperatures was not significant. Conversely, a non-negligible variation in terms of the slope of the solubility curve was observed as a function of the gas mixture composition: the curve increased more steeply as the percentage of hydrogen reduced.

Developing a numerical model for microbial methanation in a depleted hydrocarbon reservoir

Biological methanation is a promising option for CO2 utilization and energy storage. While the underground condition is not appropriate for a methanation reaction, microorganisms act as a catalyst and make the reaction possible. This study investigates the performance of biological methanation in depleted gas reservoirs using numerical simulation. To do this, a one-dimensional synthetic homogeneous depleted gas reservoir is modeled with the two-phase flow comprising components H2, CO2, CH4, and H2O. Then, the simultaneous injection of CO2 and H2 into the reservoir is numerically simulated to evaluate the methane production rate in MATLAB Reservoir Simulation Toolbox (MRST) open-source software. Long-term results show propagating composition waves and pressure profiles. Sensitivity analysis reveals that methane production is positively correlated with the initial reservoir pressure and the number of methanogenic microorganisms, but negatively correlated with the temperature and the bacterial decay rate. The bacterial growth rate has an insignificant effect on methane production in this model. The bacterial population is the most critical parameter, as 1e7 methanogenic microorganisms per cubic meter of aqueous phase can produce 96% pure methane after 12 years. Overall, the work demonstrates harnessing in-situ bio-reactions to utilize CO2 and recover depleted gas reservoirs.

Investigation into hydrogen induced fracture of cable bolts under deep stress corrosion coupling conditions

The coupling effects of geostress and multi-attribute corrosion environments are the major causes of damage and rupture of prestressed cable bolts in deep underground environments. To determine impacts of different environmental factors on stress corrosion cracking of cable bolts in underground conditions, the accelerated stress corrosion tests and finite element numerical simulations were carried out. By implementing the material diffusion theory and appreciating the hydrogen induced lattice expansion effects, the diffusion and aggregation behavior of hydrogen in cable bolts were simulated. The influences of stress intensity and hydrogen concentration on failure mechanisms of cable bolts were studied by considering the hydrogen induced expansion strain. The failure only occurred in the environments where sufficient hydrogen concentration existed. The hydrogen diffusion flux and distribution were consistent with stress concentration distribution. The prestress accelerated the hydrogen diffusion to stress concentrated position leading to a greater strain in the stressed areas, which consequently induced hydrogen expansion stress and decreased cohesion strength of lattice near crack tip. The fractographic features of failed specimen were analysed and hydrogen assisted fracture was confirmed to be one of the main failure mechanisms leading to stress corrosion failures. The methodologies proposed could be used to study the diffusion and distribution of hydrogen in metals and the obtained results improved the understanding failure mechanism of hydrogen assisted SCC.

Interaction of cemented paste backfill (CPB) and circumneutral mine water during column experiments

Cemented paste backfill (CPB) is used as a support and filler material in underground mines. In underground conditions, before mine closure and flooding, surface and groundwaters with variable quality are in contact with CPB material, which may result in the leaching of harmful substances from the CPB. In this study, we used actual mine water from a gold mine to flush CPB in a laboratory test to simulate underground conditions and the environmental influence of CPB on groundwaters more realistically than before.Different CPB materials were treated with mine water in columns for nine months. The columns were drained and filled with new mine water batches four times during the experiment to simulate intermittent flushing underground. The dissolved elemental content, major cations, pH and oxidation-reduction potential (ORP) of the waters were measured, and the chemical results were analysed by performing geochemical modelling with the widely used geochemical code PHREEQC. X-ray tomography was also used to examine the internal structure of the CPB specimens.The results demonstrated that calcium and sulphate present in CPB parent materials leached into the mine water, which might cause a deterioration of CPB. In contrast, the concentrations of dissolved As, Sb and Ni decreased in the mine water when it was in contact with CPB materials. However, arsenic started to be re-released from the materials at the end of the nine-month experimental period. The geochemical modelling suggests that the removal of metals/metalloids from the mine water was driven by the surface complexation reactions on originally present and/or freshly precipitated metal (hydr)oxide minerals. A longer and modified testing period is needed to thoroughly examine the conditions under which these adsorbed elements start to release over time.

Metagenomic sequencing reveals mechanisms of adaptation and biodegradation of dechlorinating bacteria to trichloroethylene

Bioremediation is a sustainable, cost-effective, and eco-friendly way to remediate pollutants. However, the effectiveness of bioremediation is constrained by the underground environmental conditions, resulting in poor natural attenuation of organic pollution and degradation by functional microorganisms. In this study, a dechlorinating bacteria (DB) was enriched from contaminated soil and used to degrade trichloroethylene (TCE) in wastewater. The adaptation and degradation mechanisms of DB to TCE were investigated by degradation product analysis and metagenomic sequencing. The degradation of TCE by DB is pH and additional carbon source dependent. The highest TCE removal amount (1.86 × 10−7 mmol/CFU) was achieved at pH=8, 1% DB inoculum volume, and 400 mg/L sodium acetate concentration. Moreover, DB has a high acid resistance and a removal capacity of 1.18×10−7 mmol/CFU for TCE at pH =2. None of the co-occurring pollutants Cr (VI) and toluene had a significant effect on the ability of DB to degrade TCE in wastewater (maintained at 1.13–1.22×10−7 mmol/CFU). DB dechlorinated TCE mainly through the action of extracellular enzymes (contributed 91% of the total removal ability). DB playing a major role in degradation is Paraclostridium. Significant differences in alpha diversity indices were revealed in the reaction systems after 15 days of exposure to TCE (p < 0.01). The degradation of TCE by DB is mainly accomplished through the defense system, energy synthesis, electron supply and biodegradation. Metagenomic sequencing demonstrated that DB achieved adaptation and degradation of TCE through gene-regulated biological processes such as xenobiotic biodegradation and metabolism, carbohydrate metabolism, biosynthesis of other secondary metabolites, amino acid metabolism, membrane transport, and signal transduction. This study reveals for the first time the biodegradation efficiency and biotransformation process of DB under TCE stress.

Why cave planthoppers study matters: are Cixiidae a subtroglophile lineage? (Hemiptera, Fulgoromorpha)

Planthoppers are an interesting and contrasting model among insects for studying the subterranean environments. Their morphological and ethological adaptations to the underground conditions (complete darkness, lower temperatures, high hygrometry, stability of environmental constants, rarefied food sources, etc.), and their worldwide distribution in both temperate and tropical areas make them an interesting model among invertebrates. In this review, we highlight why cave planthoppers study matters, with particular emphasis on the Cixiidae. The two hypotheses proposed, the ‘climatic relict hypothesis’ and the ‘adaptive shift’, are not sufficient enough to clearly understand and explain the drivers to cavernicoly. Phylogenetic analyses approaches might help to better document and increase our knowledge on such peculiar environments. The singularity of the distribution pattern of the adaptation to cavernicoly in planthoppers raises also interesting questions to investigate and suggest contrasting scenarios to explore further, particularly should the Cixiidae be defined as a subtroglophile lineage?

The Practicality of Resistivity Method for Recognizing Vertically Distributed Anomalies Using Simulated Models

In brownfield sites, two proposed shallow horizontal targets were numerically modelled to mimic variable underground conditions; these targets were sequenced vertically in a different manner. Synthetic 2D electrical resistivity datasets were generated using the RES2DMOD and then inverted by using RES2DINVx64. These targets have different lengths, one with a higher and the second with a lower resistivity value relative to the background resistivity. The effectiveness of dipole-dipole, Wenner, and Wenner-Schlumberger configurations was tested by conducting a qualitative comparison. The inverted resistivity images suggest that the target sequence has a significant effect on the configuration detectability. The high resistivity target was conveniently recognized when it overlies a low resistivity target. Dipole-dipole configuration showed optimum results in recognizing complicated underground conditions.

The effects and solidification characteristics of municipal solid waste incineration fly ash-slag-tailing based backfill blocks in underground mine condition

Currently, there is a limited understanding of the material performance effects and hydration mechanisms of solidified waste-based binder filling materials containing municipal solid waste incineration fly ash in the actual underground filling environment. This study utilized the Circulating Fluidized Bed (CFB) and Grate Furnace (GF) techniques to produce quadri-component uncalcined binder fill materials from municipal solid waste incineration fly ash (MSWI FA), blast furnace slag (BFS), flue gas desulfurization (FGD) gypsum, and tailings. The solidified test blocks were then cured in-situ in a void space of a certain iron underground mine in Hebei with conditions (temperature: 25-30℃, humidity: 18-19%, mine water influx: annual average of 150m3/h). The research results indicate that the mechanical performance and heavy metal solidification outcomes of these blocks surpassed those samples cured under laboratory conditions (temperature: (20±1)℃, humidity: not less than 90%), demonstrating the feasibility of using MSWI FA for underground binding and backfilling in mines. Building upon preliminary research, a binder mix proportion was established: 20wt.% MSWI FA, 70wt.% BFS, and 10wt.% FGD gypsum. Test blocks were fabricated using lead-zinc tailings sand and iron mine tailings as aggregates. All blocks met the 28-day strength requirements for typical mine backfills ranging from 1 to 6.5MPa, with the strength of the XB-M group reaching 24MPa (when cured underground). The leaching concentrations of heavy metals were all below the limits set for class III groundwater standards, with Pb, Zn, Cr, and As achieving a solidification rate of over 98% at 28 days. Microscopic hydration mechanisms indicate that the primary hydration products in the solidified body were ettringite, Friedel's salt, and C-S-H gel. The high content of reactive Al2O3 in the CFB fly ash enables the [AlO4]5- to substitute [SiO4]4-, leading to the formation of a long-chain, high polymerization C-A-S-H phase. Additionally, the abundant Cl- in GF fly ash readily reacted with [Al(OH)6]3−, forming Friedel's salt. The hydration products in the blocks cured under mine conditions significantly increased in their degree of polymerization. This provides a practical application approach for the future treatment and reuse of MSWI FA. Environmental implicationMSWI FA is classified as hazardous waste (HW18) due to its content of harmful components such as chlorides, dioxins, and soluble heavy metals, which pose potential environmental pollution risks. This study, for the first time, solidified test specimens were sent to an underground mining void in a certain iron mine in Hebei, China, for on-site curing (temperature range: 25-30°C, humidity: 18-19%, annual average mine water inflow rate: 150m3/h). The mechanical properties and the solidification performance of heavy metals in the test specimens were superior to those under laboratory curing conditions (temperature: (20±1)°C, humidity not less than 90%).

Simulation of Gas Fracturing in Reservoirs Based on a Coupled Thermo-Hydro-Mechanical-Damage Model

Gas fracturing technology for enhancing rock permeability is an area with considerable potential for development. However, the complexity and variability of underground conditions mean that a variety of rock physical parameters can affect the outcome of gas fracturing, with temperature being a critical factor that cannot be overlooked. The presence of a temperature field adds further complexity to the process of gas-induced rock fracturing. To explore the effects of temperature fields on gas fracturing technology, this paper employs numerical simulation software to model the extraction of shale gas under different temperature conditions using gas fracturing techniques. The computer simulations monitor variations in the mechanical characteristics of rocks during the process of gas fracturing. This analysis is performed both prior to and following the implementation of a temperature field. The results demonstrate that gas fracturing technology significantly improves rock permeability; temperature has an impact on the effectiveness of gas fracturing, with appropriately high temperatures capable of enhancing the fracturing effect. The temperature distribution plays a crucial role in influencing the results of gas fracturing. When the temperature is low, the fracturing effect is diminished, resulting in a lower efficiency of shale gas extraction. Conversely, when the temperature is high, the fracturing effect is more pronounced, leading to a higher shale gas production efficiency. Optimal temperatures can enhance the efficacy of gas fracturing and consequently boost the efficiency of shale gas extraction. Changes in the parameters of the rock have a substantial impact on the efficiency of gas extraction, and selecting suitable rock parameters can enhance the recovery rate of shale gas. This paper, through numerical simulation, investigates the influence of temperature on gas fracturing technology, with the aim of contributing to its improved application in engineering practices.

The negative effect of a torsion dissipative structure on the stability and bearing capacity of the yield frame support

Yieldable frame support (YFS) is the most important primary component of a tunnel or underground roadway propping in a consequent set of multistage support technology, which is employed in the squeezing rock. This research aimed to enhance the efficiency of combined support using the synergetic effect of connecting YFS to the rock bolts/cables (YFSB). Employing the methods of actual measurements and survey, computer simulation, and underground testing of YFS, we investigated conditions that provoke a spontaneous torsion of the YFS profile, which caused YFS stability failure, loss of the bearing capacity and integrity. We revealed a longitudinal twist or torsion of the YFS profile as a new mode of YFS stability failure and demonstrated that the torsion is a consequence of a scale effect. Based on the thermodynamics of irreversible processes, we proved that this torsion is a form of dangerous dissipative structure that minimizes entropy production. We investigated the torsion parameters and developed a new joint between YFS and rock bolt, which is a key element of a novel lean technology that effectively prevents the YFS profile torsion. The joint and its optimal parameters were successfully tested in an underground condition that provided YFSB stability, increased its average resistance, conserved total bearing capacity, and integrity.

METHODS FOR INCREASING THE CONDENSATE RECOVERY COEFFICIENT WHEN DEVELOPING GAS CONDENSATE FIELDS

This article will discuss methods for increasing the condensate recovery coefficient and the concept of condensate recovery. Gas condensate is a cold hydrocarbon reservoir that includes natural gas as well as liquid hydrocarbons, often in the form of liquid condensate. During reservoir extraction, liquids are mixed from mixtures of light hydrocarbons (eg methane, ethane, propane) and denser liquid hydrocarbons (known as condensates). Gas condensates are found in underground reservoirs, where temperature and pressure conditions allow the gas to condense into liquid form as it moves from the formation to the surface. Such situations are often observed in tanks where there is a combination of increased pressure, high temperatures and a specific gas composition. The condensate production indicator from the reservoir describes the level of gas condensate extraction from gas condensate and oil and gas condensate fields. A distinction is made between instantaneous condensate production (determined at a certain point in time) and final production (at the end of commercial exploitation of the field). To quantify condensate production, the condensate production indicator is used - this is the ratio between the given definition of condensate and the reserves taken from the reserves of the field based on its study (expressed as a percentage or fraction of units). This indicator is used to extract recoverable condensate reserves. In addition, it is taken into account when developing a project for a gas condensate or oil and gas condensate field, taking into account the efficiency of the technology used. The completeness of condensate removal in some cases determines the reasonableness of developing the selected system. The main features of the behavior of gas condensate systems are associated with the corresponding phenomena reflected in the phase diagrams of reverse condensation and evaporation. These features lead to the fact that when the pressure in the gas condensate system decreases to a level below the saturation pressure, condensation of heavier hydrocarbons (condensate) occurs. If the pressure in the gas condensate formation during development is maintained at the initial level (or the pressure at the beginning of condensation), then phase transitions occur only in the formation zones adjacent to the well. This requires taking into account changes over time, such as changes in filtration characteristics in the bottomhole zones of wells. When developing a gas condensate field to the point of depletion, condensate begins to fall out everywhere in the reservoir. However, the condensate that falls often has little effect on the gas saturation coefficient of the entire formation. Consequently, when developing a gas condensate field until depletion (with a low condensate content in the gas), filtration flows can be considered as single-phase, since the precipitated condensate remains motionless. Low condensate saturation of the formation leads to slight changes in its capacitive and filtration characteristics. In the zone of the bottomhole space of the formation, two-phase filtration occurs. Keywords: gas, gas condensate, heavier hydrocarbons, dew point, the condensate recovery coefficient.

Experimental study of the effect of contact line profiles on the wear mechanism of a skateboard

Using an experimental approach, the researchers investigated the wear of a skateboard according to different profile contact lines. A high-speed current-carrying test machine was used to simulate underground railway operational conditions and obtain parameters such as the coefficient of friction, arc discharge energy, temperature increase, current-carrying efficiency, and offline rate of friction pairs comprising a skateboard and contact lines with varying profiles. The researchers analysed the impact of experimental parameters on skateboard wear matched with the different contact lines, as well as the wear mechanism of the skateboard. The experimental results revealed the following order for the total skateboard wear when matched with different contact lines: oblique contact line > pitted contact line > normal contact line. For the total skateboard wear with oblique contact line, the electrical wear of the skateboard predominantly contributed to the overall wear. Across all experiments, the total skateboard wear when matched with the oblique and pitted contact lines reached 10.291 g and 5.537 g, respectively, which was approximately 3.232 and 1.739 times the wear observed when matched with the normal contact line (3.184 g). With other experimental parameters held constant, the skateboard wear was directly proportional to current and sliding velocity, but inversely proportional to the normal load. The effect of sliding velocity on skateboard wear, arc energy, offline rate, etc., was less significant than the impact of current and normal load, especially at low speeds.

Geophysical techniques for modeling mine structure and tectonic disturbances

This article presents the results of modeling the structural structure of a rock mass during underground mining operations. The research was carried out at one of the largest mining and processing plants in the Republic of Kazakhstan – Donskoy GOK. The spectral seismic profiling method, which has proven itself well for working in underground conditions, based on the seismoacoustic properties of the rock mass, was chosen as a tool for diagnosing the array. The purpose of the research was to diagnose the structural structure of the mine field in order to select the locations of drainage wells intended for drainage of mine workings and ore body. As a result of the research carried out, a structural model of each horizon and the mine as a whole was built, which allows us to determine with sufficient reliability the most promising sites for drainage work. In addition, the results obtained will be used to design vertical mine workings within the studied area. The results obtained were confirmed by verification drilling and proved their effectiveness and reliability.

A complex method for preventing collisions between mining equipment and personnel in mine conditions

The article provides an analysis of low-frequency and high-frequency methods for determining the distance between mobile equipment and personnel for the purpose of preventing collisions in difficult mine conditions. The authors assessed the influence of the geology of mine workings, the earth’s surface and transport on the electromagnetic field of the VLF, LF and C range. From the analysis, a combined design solution was derived for determining the distance in surface and underground mining conditions. The proposed methods for registering the proximity of objects compensate for each other’s vulnerabilities and make it possible to implement an integrated approach to preventing collisions of mining equipment with personnel.

Straightness Measurement Based on FOG-IMU and Shearer Motion Constraints for Longwall Coal Mining

Straightness measurements of fully mechanized coal faces are a core requirement for intelligent, comprehensive coal mining. In coal mining, using an inertial measurement unit (IMU) assisted by an odometer for straightness measurement is vital for automating longwall mining. IMUs are less vulnerable to dim and harsh underground mining conditions. However, IMU divergence cannot be controlled solely by the forward velocity obtained from the odometer. To address this problem without external sensors, this paper proposes a straightness measurement method based on a fiber optic gyroscope-IMU/odometer and shearer motion constraints. The motion of the shearer is constrained to correct the pitch and roll attitude angle errors in strapdown inertial navigation solution (SINS) attitude solutions. An extended Kalman filter was established to combine the SINS and dead reckoning using the output from the odometer. Finally, the position estimation obtained by Kalman filter fusion was converted into straightness. An experiment based on a custom-built test rail demonstrated that the proposed algorithm effectively improved the accuracy of straightness measurements in multiple cutting cycles. The error of the results in the horizontal plane was reduced by 45% compared to the traditional IMU/odometer method. This study is important in promoting the unmanned and intelligent development of China’s coal industry.

Renovation of the retention bunker lining on the example of the Mysłowice-Wesoła coal mine

The scientific article focuses on the analysis, renovation and modernization of the retention bunker No. 4 at the 465 m level in the Mysłowice-Wesoła coal mine complex. This bunker, a key part of the mining infrastructure, has an important function in the coal mining process, accumulating output before its further transport to the surface. During a regular inspection of the bunker, significant damage was found in the form of defects on the lining, caused by the impacts of the output flow. Repair efforts required a comprehensive approach, including the use of rope access techniques (industrial mountaineering) for precise damage assessment and repair. The research and repair work included the installation of rappelling stations, rope access rappelling, non-destructive testing, bolting, concrete encasement of the damage, and other innovative repair techniques. Careful adaptation of operations to underground conditions and precise planning of logistics and repair work were key to successfully restoring the bunker’s stability and functionality. An analysis of the renovation process reveals the comprehensiveness of the measures, covering both the north and south sides of the bunker. The use of bolting, steel mesh, and innovative approaches allowed for the successful repair of damage. The ultimate success of the renovation helped minimize the risk of further damage and restore the integrity of the No. 4 retention bunker. The article also highlights the often-downplayed role of bunker in mining infrastructure, arguing that despite having ready-made longwalls and roadways, the absence of a functional bunker makes a coal mining system incomplete.