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Slit tube responses and rock fracture characteristics in slit charge blasting under high in situ stress

AbstractDeep mining of natural resources, like coal, is increasingly utilizing directional blasting technology with slit charge for rock blasting at greater depths. This study, based on numerical simulation methods, analyzes the dynamic behavior of slit charge blasting in three aspects: slit tube dynamic response, hoop stress evolution, and crack propagation. According to research findings, the failure mode of the slit tube mainly manifests as a tensile fracture of the inner wall and a shear fracture at the end connection, where the end connection of the slit tube is the weak point of the overall structure. The dynamic response of the slit tube mainly exhibits radial response in the vertical direction of the slit and hoop response in the slit direction. The hoop tensile stress plays a crucial role in determining the spread of cracks caused by explosions. As the in situ stress increases, the peak hoop tensile stress reduces, and the peak hoop compressive stress increases. This hinders the propagation of cracks. In addition, the directional impact is most pronounced in the middle of the borehole, with the longest primary directional crack observed. Conversely, the directional impact is least favorable near the bottom of the borehole. When the in situ stress reaches 60 MPa, the purpose of directional fracture has not been achieved, suggesting combining presplit blasting for in situ stress relief to improve rock breaking efficiency.

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The effect of thermal–hydro–mechanical coupling on grouting in a single fracture under coal mine flowing water conditions

AbstractGroundwater inrush is a hazard that always occurs during underground mining. Grouting is one of the most effective processes to seal underground water inflow for hazard prevention. In this study, grouting experiments are conducted by using a visualized transparent single‐fracture replica with plane roughness. Image processing and analysis are performed to investigate the thermo–hydro–mechanical coupling effect on the grouting diffusion under coal mine flowing water conditions. The results show that higher ambient temperature leads to shorter initial gel time of chemical grout and leads to a better relative sealing efficiency in the case of a lower flow rate. However, with a higher water flow rate, the relative sealing efficiency is gradually reduced under higher temperature conditions. The grouting pressure, the seepage pressure, and the temperature are measured. The results reveal that the seepage pressure shows a positive correlation with the grouting pressure, while the temperature change shows a negative correlation with the seepage pressure and the grouting pressure. The “equivalent grouting point offset” effect of grouting shows an eccentric elliptical diffusion with larger grouting distance and width under lower temperature conditions.

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Open Access
A perspective review of applications of the computed tomography (CT) scan imaging technique for microscopic reservoir rock characterization

AbstractIn hospitals, a medical computed tomography (CT) scan is used to detect damage to infected areas of the human body. Using this technology, scientists and engineers have found a way to detect the internal pore connections and characterize rock samples of oil and gas reservoirs in the petroleum industry. Nowadays, the micro‐CT scan technique is gaining considerable interest in reservoir rock characterization and in situ monitoring of fluid flow through porous media during different flooding experiments. Along with this digital rock physics (DRP) idea, images have been used to accurately describe and model for simulations of rock samples. In this review, the application of micro‐CT and medical‐CT scanning in the oil and gas industry has been thoroughly discussed. Recent improvements in DRP and modern imaging techniques in the oil and gas industry have been modeled using both experimental and simulation work. The combination of a DRP study and a CT scan has also been discussed as a unique idea for the current scenario of research work in this field. The available literature shows that the modern imaging technique and the DRP concept can enable an understanding of the pore network model. It has also been observed that the visualization of fluid flow behavior through porous media is now possible during fluid movement through the core samples. This review contributes to the new research area and aids those in this field in quickly gaining an understanding of applied image techniques in the oil and gas industry.

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Open Access
Corrosion effect of hydrochloric acid on the granite: Insights from electrical conductivity, mineral composition, and tensile behavior

AbstractHydrochloric acid (HCl) extensively exists in deep underground projects, arising from the transportation of industrial raw materials or fracturing fluids of petroleum engineering. It results in corrosion, which can significantly impact the stability of surrounding rock structures. Therefore, in‐depth analysis of the degradation of rock corroded by the HCl solution is an essential task for underground engineering. In this study, the granite specimens are initially treated with the HCl solution with various concentrations. Then, the tests and analyses, such as electrical conductivity (EC) measurements, mineral composition assays, and Brazilian splitting tests, are employed to investigate the corrosion mechanism of the HCl solution. Our results and findings are generally as follows: (1) As the immersion time increases, the EC exhibits a relatively high level at pH value of 1, a decreasing trend at pH value of 3, and an increasing trend at pH value of 5 and 7. (2) The HCl solutions with various concentration have different effect on mineral composition, characterized by an increase in proportion of SiO2 and a reduction in proportion of Na2O, Al2O3, K2O, MgO, and CaO, as the solution pH value decreases. (3) After immersion in the solutions with pH values of 1, 3, and 5, the tensile strength of the granite decreases by 23.85%, 20.84%, and 20.24%; the average stiffness of the specimen decreases by 29.29%, 23.43%, and 11.97%; the proportion of releasable energy increases by 6%, 4%, and −2%; the releasable energy decreases by 54.96%, 26.09%, and 14.52%; and the dissipated energy decreases by approximately 68.85%, 41.39%, and 5.41%, respectively. (4) The evolution of physical and mechanical properties of the immersed granite specimen can be analyzed from a chemical aspect. The corrosive action of HCl cleaves Si–O and Al–O chemical bonds within the granite, particularly altering the tetrahedral structures of its silicate components. This process involves breaking existing chemical bonds and the formation of new ones, ultimately destroying the silicate molecular structures. As the concentration of HCl increases, the rate of these reactions accelerates, progressively weakening the chemical bonds and consequently deteriorating the mechanical characteristics of the granite. These findings can deepen our knowledge about the corrosion effect of HCI solutions on natural surrounding rocks and serve as references for further research on rock corrosion mechanisms in underground engineering.

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Open Access
Hotspots, trends, and regional focus on oil or gas exploration: A bibliometric comparative study

AbstractOil and gas resources serve as the driving force for economic and social development. This rapid development of science and technology has accelerated the exploration, development, and utilization of oil and gas resources, and thus led to spurts in related research. However, the research trends in global oil and gas exploration vary with the progress of science and technology as well as social demands. Accordingly, they are not easily captured. This study explores the research trends in global oil and gas exploration through the bibliometric analysis of 3460 articles on oil and gas exploration collected from the Web of Science database and published from 2013 to 2023. The research hotspots, objects, regional distribution, methods, and evaluation methods in oil and gas exploration are analyzed, and the direction of development of oil and gas exploration is presented on this basis. The research characteristics of four major countries or regions related to oil and gas exploration were further investigated and compared. The results show that the number of publications on oil and gas exploration research has been continuously increasing in the past decade, with China ranking the top in terms of publications. Given the continuously evolving global energy demand, exploration of unconventional oil and gas, application of digital technology, deep and emerging regional resource exploration, and environmentally friendly and low‐carbon source exploration will be future research hotspots.

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Open Access
Experimental study on dynamic behavior analysis of coal and its acoustic emission response characteristics under impact failure

AbstractIn coal mines, dynamic disasters such as rock bursts seriously threaten the safety of mining activities. Exploring the dynamic behaviors and disaster characteristics in the impact failure process of coal serves as the basis and prerequisite for monitoring and warning rock bursts. In this context, impact failure tests of coal were carried out under different axial static loads and impact velocities to analyze the dynamic behaviors and acoustic emission (AE) response characteristics of coal. The results show that the dynamic behaviors of coal under combined dynamic and static loads are significantly different from those under static loads, and the stress‐strain curve displays double peaks without an obvious compaction stage. As the axial static load grows, the dynamic strength and peak strain both have a quadratic function with the axial static load. When the coal damage intensifies instantaneously, the AE count and energy parameters both witness pulse‐like increases and reach their peak values. The damage effect of axial static loads on coal, though limited, has an extreme point. In contrast, the impact velocity can strengthen the response of AE signals and has linear function relationships with the peak values of AE count and energy. This plays a leading role in the damage to samples and sets a critical point for coal failure and fracture. Compared with the analysis results of stress and strain, the responses of AE signals are more accurate and reliable. Based on AE response characteristics, the damage evolution process of coal under the combined dynamic and static loads can be identified more accurately to reveal the moment corresponding to coal damage and the characteristics of coal failure. The research results are conducive to the further application of AE monitoring methods to early warning of rock burst disasters in coal mining sites.

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Open Access
Laboratory evaluation of a low‐cost micro electro‐mechanical systems sensor for inclination and acceleration monitoring

AbstractIn this study, the design and development of a sensor made of low‐cost parts to monitor inclination and acceleration are presented. Α micro electro‐mechanical systems, micro electro mechanical systems, sensor was housed in a robust enclosure and interfaced with a Raspberry Pi microcomputer with Internet connectivity into a proposed tilt and acceleration monitoring node. Online capabilities accessible by mobile phone such as real‐time graph, early warning notification, and database logging were implemented using Python programming. The sensor response was calibrated for inherent bias and errors, and then tested thoroughly in the laboratory under static and dynamic loading conditions beside high‐quality transducers. Satisfactory accuracy was achieved in real time using the Complementary Filter method, and it was further improved in LabVIEW using Kalman Filters with parameter tuning. A sensor interface with LabVIEW and a 600 MHz CPU microcontroller allowed real‐time implementation of high‐speed embedded filters, further optimizing sensor results. Kalman and embedded filtering results show agreement for the sensor, followed closely by the low‐complexity complementary filter applied in real time. The sensor's dynamic response was also verified by shaking table tests, simulating past recorded seismic excitations or artificial vibrations, indicating negligible effect of external acceleration on measured tilt; sensor measurements were benchmarked using high‐quality tilt and acceleration measuring transducers. A preliminary field evaluation shows robustness of the sensor to harsh weather conditions.

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Open Access