Search Results (1,880)

Boreholes in the Teleghma region of northeastern Algeria discharge thermal water with temperatures between 40 and 49 °C and total dissolved solids (TDS) ranging from 570 to 940 mg/L. The stable isotope compositions range from –7.8‰ to –6.2‰ for δ¹⁸O and –52.6‰ to –43.3‰ for δ²H, indicating a meteoric origin. Based on these isotopic signatures, the water is classified as immature and undersaturated with respect to the equilibrium line on the Giggenbach Na–K–Mg ternary diagram. The water exhibits a sodium–chloride (Na–Cl) facies, closely associated with Triassic formations rich in evaporitic deposits. This association was confirmed by the IIGR method, which illustrates the chemical evolution of the hydrothermal fluid as it ascends from the karstic carbonate reservoir through conduits and traverses clay formations. Consequently, computed saturation indices and applied inverse modeling significantly contributed to understanding the interactions between the hydrothermal water and the traversed rock. At the local scale, halite dissolution is the primary mineral phase driving chemical changes. Regionally, however, the processes are dominated by gypsum dissolution and cation exchange reactions between calcium and sodium ions. These findings offer valuable insights into the geochemical processes that shape the Teleghma geothermal system, with implications for resource management and potential applications. Full article

The accurate real-time delineation of overburden failure zones, specifically the caved and water-conducted fracture zones, remains a significant challenge in longwall mining, as conventional monitoring methods often lack the spatial continuity and resolution for precise, full-profile strain measurement. Based on the hydrogeological data of the E9103 working face in Hengjin Coal Mine, a numerical calculation model for the overburden strata of the E9103 working face was established to simulate and analyze the stress distribution, failure characteristics, and development height of the water-conducting fracture zones in the overburden strata of the working face. To address this problem, this study presents the application of a distributed optical fiber sensing (DOFS) system, centering on an innovative fiber installation technology. The methodology involves embedding the sensing fiber into boreholes within the overlying strata and employing grouting to achieve effective coupling with the rock mass, a critical step that restores the in situ geological environment and ensures measurement reliability. Field validation at the E9103 longwall face successfully captured the dynamic evolution of the strain field during mining. The results quantitatively identified the caved zone at a height of 13.1–16.33 m and the water-conducted fracture zone at 58–60.6 m. By detecting abrupt strain changes, the system enables the back-analysis of fracture propagation paths and the identification of potential seepage channels. This work demonstrates that the proposed DOFS-based monitoring system, with its precise spatial resolution and real-time capability, provides a robust scientific basis for the early warning of roof hazards, such as water inrushes, thereby contributing to the advancement of intelligent and safe mining practices. Full article

A vast number of boreholes in underground mining operations are often plagued by deviation issues, which severely impact both production efficiency and safety. The accurate and rapid acquisition of borehole trajectories is fundamental for subsequent deviation control and correction. However, existing inclinometers are limited by their operational efficiency and estimation accuracy, making them inadequate for large-scale measurement demands. To address this, this paper proposes a novel method for the rapid and accurate reconstruction of underground mine borehole trajectories using a robotic system. We employ a custom-designed robot equipped with an Inertial Measurement Unit (IMU) and a displacement sensor, which travels stably while collecting real-time attitude and depth information. Algorithmically, a complementary filter is used to fuse data from the gyroscope with that from the accelerometer and magnetometer, overcoming both integration drift and environmental disturbances. A cubic spline interpolation algorithm is then utilized to time-register the low-sampling-rate displacement data with the high-frequency attitude data, creating a time-synchronized sequence of ‘attitude–displacement increment’ pairs. Finally, the 3D borehole trajectory is accurately reconstructed by mapping the attitude quaternions to direction vectors and recursively accumulating the displacement increments. Comparative experiments demonstrate that the proposed method significantly improves efficiency. On a complex trajectory, the maximum and mean errors were reduced to 0.38 m and 0.18 m, respectively. This level of accuracy is far superior to that of the conventional static point-by-point measurement mode and effectively suppresses the accumulation of dynamic errors. This work provides a new solution for routine borehole trajectory surveying in mining operations. Full article

This article presents an original, multi-depth soil-temperature monitoring system based on TMP117 digital sensors designed for deployment at several depths. The objective was to evaluate the system’s accuracy and applicability for building-energy performance assessment under contemporary climate conditions. Urban measurements at depths between 1.0 and 2.0 m were compared with ground temperatures derived using PN-EN 16798-5-1:2017-07 with Typical Meteorological Year (TMY) inputs and with observations from the Polish Institute of Meteorology and Water Management (IMWM). Standard inputs underestimated soil temperature on average by 1.1–2.3 °C (TMY) and 2.0–2.8 °C (IMWM), with the bias increasing with depth. For a ground-to-air heat-exchanger (GAHE) assessment, energy benefits estimated from standard inputs were lower in measurements by approximately 30–60% for pre-cooling and 70–86% for pre-heating. Measurements also revealed location-dependent differences between boreholes attributable to underground infrastructure. These findings indicate that non-local or outdated climate datasets can materially overestimate GAHE potential and confirm the need for local, multi-depth ground measurements and periodic updates of standard climate inputs to reflect urbanized conditions and climate change. The presented system constitutes a practical, scalable tool for engineers and designers of HVAC systems relying on ground heat exchange. Full article

Focusing on the mining-induced fracture development characteristics of Weakly Cemented Overburden (WCO) in Ultra-Thick Coal Seam (UTCS) extraction, this study, based on the 1101 first mining face in Xinjiang’s Zhundong Coalfield, systematically investigates the dynamic evolution law of the water-conducting fracture zone (WCFZ) in WCO by employing similarity simulation, quantitative characterization using Fractal Dimension (D), and surface borehole exploration and borehole imaging technology. The results show that existing prediction equations for the WCFZ have poor applicability in the study area, with significant fluctuations in prediction outcomes. Similarity simulation reveals that Thick Soft Rock Layers (TS) guide and control fracture development, with the D exhibiting a “step-like” evolution. After the first rupture of TS1, the peak D reaches 1.49, stabilizing between 1.36 and 1.37 after full extraction. The height of the WCFZ increases non-linearly with the advance of the working face, reaching a maximum of 189 m, with a fracture-to-mining ratio of 10.5. Based on D fluctuations and extension patterns, the fracture development is divided into three stages, initial development, vertical propagation, and stabilization, clarifying its spatial evolution. Field measurements indicate a WCFZ height ranging from 161 to 178 m, with a fracture-to-mining ratio of 9.73–12.18, showing only a 6.2% error compared to the simulation results, which verifies the reliability of the experiment. This study reveals the evolution mechanism of the WCFZ during mining in UTCS and WCO in the Zhundong area, providing a theoretical basis and practical guidance for mine disaster prevention and control, as well as safe and efficient mining. Full article

Water inrush disasters pose a serious threat during tunnel construction. Accurately evaluating their evolution process is essential for timely prevention and risk mitigation. Given the staged nature of seepage-instability-induced inrushes and the sensitivity of borehole resistivity imaging to water-bearing anomalies, this study explores the use of borehole resistivity methods to monitor the evolution of such events. A four-stage geoelectrical evolution model is developed based on the characteristics of inclined fault-related water inrushes. A time-lapse evaluation method combining least squares inversion and resistivity ratio analysis is proposed to assess the inrush process. Numerical simulations show that this method achieves a localization error below 2 m for inclined water-conducting channels. Across the four stages, the resistivity ratio of the channel ranges from 0.65 to 1.40, capturing the three-dimensional expansion of the inrush pathway. These findings confirm that borehole resistivity imaging effectively characterizes the evolution of water inrush disasters and supports early warning and mitigation strategies. Full article

To investigate the distribution of coal seam stress ahead of the working face under hard-roof conditions and analyze its impact on gas flow, this study focused on the 16,021 working face in Wu Hua No. 1 Mine. First, we established a mining model using UDEC to analyze stress distribution at different coal seam extraction distances. Second, we used COMSOL Multiphysics 6.3 to simulate the influence of stress on the permeability and gas pressure of coal seams during extraction, thereby exploring how stress distribution affects gas flow. Finally, we deployed gas extraction boreholes to validate the gas flow characteristics associated with the stress zones. The results indicate that the coal seam stress ahead of the working face forms four distinct zones, influenced by the main roof hanging: stress reduction zone I, stress concentration zone, stress reduction zone II, and original stress zone. When extraction days are equal, under high-stress conditions, the extracted coal seam exhibits low permeability and a small decrease in gas pressure, making gas extraction difficult; in contrast, under low-stress conditions, it exhibits high permeability and a large decrease in gas pressure, making gas extraction relatively easier. Field measurements show that the gas extraction flow rate initially increases and then decreases with distance from the coal wall, exhibiting a noticeable rise within the 47–62 m range before stabilizing. This trend aligns well with the characteristics of stress zoning. Full article

The three-soft coal seam, characterized by its soft and fractured lithology, is prone to significant drilling trajectory deviation during construction, severely compromising gas drainage efficiency and posing potential safety hazards. In order to clarify the variation law of the drilling trajectory of the three-soft coal seam, this paper takes the 14205 working face of a mine in Guizhou Province as the engineering background, monitors and analyzes the drilling inclination and the change in the inclination, and then studies the influencing factors of the drilling deviation. During on-site drilling and coring operations and data monitoring, the formation lithology and fragmentation conditions were clarified, and the trajectories of gas drainage drilling holes at 15°, 30°, 45°, 60°, 75°, and 90° were obtained. It was observed that when the hole inclination is 15° or 90°, the change Δ value of the hole inclination is close to 0°. When the hole inclination is 30° or 75°, the change Δ value of the hole inclination is close to 2.5°. When the hole inclination is 45° or 60°, the change Δ value of the borehole inclination angle is close to 4.5°. The curve of the change Δ value of the borehole inclination angle and the borehole inclination angle was obtained by calculation and fitting, and the whole presents a quadratic function distribution. It was inferred that when the inclination angle of the borehole is 50°, the change Δ value of the inclination angle of the borehole reaches the maximum value, which is close to 5°, that is, the deflection of the gas drainage borehole is the largest. With the help of this curve, the deflection was predicted, controlled, and reduced. The AHP analysis model was used to rank the importance of the influencing factors of the borehole trajectory, and it was clear that the main controlling factor of the borehole deflection is the geological factor. This study provides a basis for obtaining the drilling deflection law and determining the appropriate drilling deflection control and correction technology. Full article

The purpose of the study is to evaluate the environmental performance of two systems for space heating and hot water provision in a residential building. In both cases, a ground-source heat pump is used. In the baseline system, the heat pump is driven by electrical power from the grid. In the alternative system, photovoltaic thermal collectors are integrated into the building for domestic hot water preparation and the production of electricity. Excess heat produced in the summer is introduced to the borehole and extracted later, in the cooler part of the year. Environmental benchmarking of the two systems was conducted using the Life Cycle Assessment method. A cradle-to-grave approach was applied, taking into account all life cycle stages of the system and its operation over 20 years. Results show that the alternative system yields significantly lower impacts in terms of Global Warming Potential (36% decrease) and Resources (36% decrease). In terms of Human Health, the decrease is minor (6%). However, in terms of Ecosystem, the alternative system shows a 47% higher impact than the baseline system. This increase is primarily attributed to the additional components required in the alternative configuration. Full article

When drilling inclined and horizontal sections, a significant part of the drill string is in a compressed state which leads to a loss of stability and longitudinal bending. Modeling of the stress–strain state (SSS) of the drill string (DS), including prediction of its stability loss, is carried out using modern software packages; the basis of the software’s mathematical apparatus and algorithms is represented by deterministic statically defined formulae and equations. At the same time, a number of factors such as the friction of the drill string against the borehole wall, the presence of tool joints, drill string dynamic operating conditions, and the uncertainty of the position of the borehole in space cast doubt on the accuracy of the calculations and the reliability of the predictive models. This paper attempts to refine the actual behavior of the drill string in critical and post-critical conditions. To study the influence of dynamic conditions in the well on changes in the SSS of the DS due to its buckling, the following initial data were used: a drill pipe with an outer diameter of 88.9 mm and tool joints causing pipe deflection under gravitational acceleration of 9.81 m/s² placed in a horizontal wellbore with a diameter of 152.4 mm; axial vibrations with an amplitude of variable force of 15–80 kN and a frequency of 1–35 Hz; lateral vibrations with an amplitude of variable impact of 0.5–1.5 g and a frequency of 1–35 Hz; and an increasing axial load of up to 500 kN. A series of experiments are conducted with or without friction of the drill string against the wellbore walls. The results of computational experiments indicate a stabilizing effect of friction forces. It should be noted that the distance between tool joints and their diametrical ratio to the borehole, taking into account gravitational acceleration, has a stabilizing effect due to the formation of additional contact force and bending stresses. It was established that drill string vibrations may either provide a stabilizing effect or lead to a loss of stability, depending on the combination of their frequency and vibration type, as well as the amplitude of variable loading. In the experiments without friction, the range of critical loads under vibration varied from 85 to >500 kN, compared to 268 kN as obtained in the reference experiment without vibrations. In the presence of friction, the range was 150 to >500 kN, while in the reference experiment without vibrations, no buckling was observed. Based on the results of this study, it is proposed to monitor the deformation rate of the string during loading as a criterion for identifying buckling in the DS stress–strain state monitoring system. Full article

CO₂ fracturing (CO₂-Frac) is a novel technology for coal mine gas control, which is distinct from CO₂ Enhanced Coalbed Methane, and has been applied to alleviate in situ stress concentration and to eliminate coal and gas outbursts in coal mines. However, the reasons for the greatly varying effects of CO₂-Frac application among different regions remains largely unknown, and the influence of geological structures, particularly pre-existing fracture orientations, remains poorly understood. The equipment system of phase fracturing and permeability improvement of low-permeability coalbed methane and the gas phase fracturing and permeability improvement technology are studied and analyzed, and the engineering application is carried out in the head face of Xinyuan Coal Mine. This study conducted three CO₂-Frac experiments in the Xinyuan coal mine in which borehole orientations were varied, with the primary fracture strike of coal seam #3 in the Shanxi Formation ranging from N3°E to N15°E. The characteristics of reservoir stress redistribution after CO₂-Frac and its mechanism controlled by the orientation of primary fractures were explored based on the analysis of microseismic focal mechanisms. The results showed that (1) Both the fracturing section and the buffer section determined the stress relief effect of CO₂-Frac. While the different experiments showed largely similar stress relief effects of the fracturing section, the effects of the buffer section greatly differed. (2) The microseismic events generated by the CO₂-Frac in the borehole with an N–S orientation showed a more concentrated spatial distribution, with higher proportions of tensile and dip-slip events. (3) The range of the stress relief in the buffer section of the borehole with an N–S orientation exceeded those of the other sections. Further geological analysis revealed that higher stress relief was achieved in both boreholes with a N–S orientation and a smaller angle between the borehole direction and the primary fracture orientation (angle BF). An improved numerical calculation model that integrated fracture mechanics and gas reservoir engineering was used in this study; the result showed that an improved CO₂-Frac effect was achieved under a BF angle of 0–21°, in good agreement with the field experiment results. The results of this study can help improve the effectiveness of CO₂-Frac and reduce the occurrence of coal and gas outbursts. Full article

Since the 2000s, Burkina Faso has experienced a rapid mining expansion with more than one hundred sites established, leading to increased waste generation often discharged untreated into the environment. Assessing water quality in these areas is therefore critical to mitigate environmental degradation and public health risks. This study develops a site-specific water quality index (WQI) for a gold mining area in Bam Province, Burkina Faso, with the objective of improving pollution monitoring and management in relation to tailing dams. Surface and groundwater samples were collected between 2021 and 2024. Physico-chemical and bacteriological analyses of groundwater sources including wells, piezometers and boreholes revealed that several parameters such as pH, turbidity, nitrates, sulphates, total iron, aluminium, arsenic, cadmium, cyanide and total and faecal coliforms exceeded international drinking water standards. Geospatial techniques were employed to identify the main contamination sources: domestic wastewater, industrial and artisanal mining and agricultural runoff. The evolution of these parameters in relation to the dynamics of soil occupation and the influence of geological structure has enabled the distinction of key parameters associated with discharges. Although individual contaminant levels were mostly moderate, their combined effects pose a significant long-term risk to ecosystems and human health. The tailored WQI is suitable for both surface water and groundwater. It provides an integrated tool for classifying and monitoring water quality in mining environments, supporting evidence-based decision making in the management of tailing dams, environmental protection and public health. Full article

Over the past five decades, the Tallet Alsauda district of Aleppo (Syria) has experienced multiple catastrophic collapses, attributed to a network of subsurface chalk cavities formed through historic quarrying and possible natural karstification. Yet, no comprehensive investigation has previously been conducted to characterise the cavities or clarify the governing failure mechanisms. Such assessments are particularly difficult in historic urban environments, where void geometries are irregular, subsurface data scarce, and underground access limited. This study addresses these challenges through an integrated programme of fourteen boreholes, laboratory testing, and inverse-distance interpolation to reconstruct subsurface geometry and overburden thickness. These data-informed three-dimensional finite element simulations are designed to test the hypothesis that chalk deterioration, driven by both natural and anthropogenic processes, controls the instability of cavity roofs. Rock mass parameters, particularly the Geological Strength Index (GSI), were progressively reduced and evaluated against the site’s documented collapse history. The simulations revealed that a modest decline in GSI from ~53 to 47 precipitated abrupt displacements (>300 mm) and upward-propagating plastic zones, consistent with field evidence of past collapses. These results confirm that instability is governed by threshold reductions in material strength, with sewer leakage identified as a principal trigger accelerating chalk softening and roof destabilisation. Full article

The process of exploiting hydrocarbon deposits is subject to many complications, some of which can make exploitation very difficult or impossible. These factors include damage to the wellbore zone by drilling fluid, which impedes the flow of reservoir fluid from the production zone to the well. This article presents the results of research conducted to develop drilling fluid compositions with the best possible ability to form a tight sealing sediment on the borehole wall. In addition to traditional carbonate blockers, modern organic agents were used as bridging agents. Research was conducted on the selection of the drilling fluid composition, the rheological parameters of which would ensure the suspension of the solid phase in the form of various types of blockers. After preparing the base drilling fluid, its composition was modified by adding different configurations of blockers. The sets of blockers added to the fluid varied in both chemical structure and particle size. Such modified fluids were then subjected to tests of technological properties, such as rheological parameters, API filtration, and pH. In the next stage, sealing tests of the filter cake formed by the tested fluids were carried out on the surface of the rock core using the PPT—Pore Pressure Transmission Test. Based on the obtained results, it can be concluded that the new type of organic blockers used allows the rapid formation of a tight filter cake on the borehole wall, and thus significantly reduces drilling fluid filtration. During PPT, the sediment formation time (t_pmax) for OB2 was 45 min; for the combination of OB1 and the carbonate inhibitor, it was 8 min; and for the carbonate inhibitor alone, it was 150 min. Full article

In many decarbonization scenarios, heat pumps are seen as a key technology for future heating needs. However, market shares for large-capacity heat pumps are still low despite the potential for significant CO₂ reduction. In particular, boiler replacements face the obstacle of insufficient heat sources due to restrictions imposed by the built environment. In this study, overcoming the restriction of individual heat sources through dual-source integration has been investigated, both by simulation and field monitoring. The results confirm that by downsizing the individual heat sources, limitations relating to noise emissions or drilling space can be overcome. For instance, by combining the ground as a heat source for 50% of the peak load coverage with outdoor air as the base load heat source, the length of the borehole heat exchanger can be reduced by up to 80% compared to when using only the ground as a heat source. Through regeneration of the ground, boreholes can be drilled closer together, and their length can be reduced by more than 50%. Cost-optimal regeneration rates were found to be between 40 and 80%. The related cost savings can make the dual-source system more cost-effective than a single-source system, even without limitations on any individual heat source. Simulation results are verified in a pilot and demonstration (P&D) plant for a boiler replacement in two larger multi-family homes. The first winter measurements confirm the basic simulation results. CO₂ saving potentials are estimated to be around 90%. Ongoing monitoring will further verify results and derive standard configurations and best practices. Full article