Deep Underground Science and Engineering最新文献

The essence of the outburst–rock burst compound dynamic disaster is the disaster behavior of the “gas-coal-surrounding rock” system under the comprehensive action of the stress field and the seepage field. Based on the geological occurrence characteristics of coal and rock in the roof, coal, and floor, this study combined experimental research and theoretical analysis to explore the effects of confining pressure, gas pressure, and axial loading rate on the mechanical behavior of gas-bearing rock–coal–rock combination structures (“RCR combination”). The results show that both decreasing gas pressure and increasing confining pressure can improve the deformation capacity and bearing capacity of the RCR combination. When the gas pressure decreases from 1.5 to 0.5 MPa and the confining pressure increases from 3 to 9 MPa, the peak stress of the RCR combination increases by 15.83% and 184.02%, respectively. On increasing the axial loading rate, the peak stress of the RCR combination first increases and then decreases, and the elastic modulus continues to decrease. There is a good correspondence between stress and acoustic emission counts (AE), which can be used as a predictive index for judging rock fracture instability. Compared with rock, coal exerts much greater influence on the mechanical strength of the RCR combination. The theoretical analysis shows that the parameters m and F₀ mainly affect the peak stress of the RCR combination, and the speed of stress reduction after the peak of the RCR combination is influenced by the parameter m. The coal elastic modulus exerts greater influence on the bearing capacity of the RCR combination than the rock elastic modulus. When the elastic modulus of rocks increases from 10 to 25 GPa and that of coal increases from 2 to 5 GPa, the peak stress of the RCR combination increases by 9.87% and 8.97%, respectively.

Traffic-induced ground vibrations cause significant problems for residents and nearby structures. Reducing the effect of these vibrations on the neighboring environment is a key challenge, particularly in urban areas. This study presents both numerical and experimental investigations of the performance of mass scatters for screening ground vibrations. A three-dimensional numerical model is validated and extended to conduct a comparative study on the efficiency of three geotechnical methods of isolation. These methods include trench barriers, wave-impeding blocks (WIBs), and mass scatters. The results showed that mass scatters represent an efficient way of scattering ground vibrations, and their efficiency is mainly related to the weights of mass scatters and their natural frequency, which control the dynamic soil response in the frequency domain. Rigid trench barriers are less effective than soft ones, and their efficiency is more pronounced regarding the WIB. Soft barriers with a depth of an order of half of the wavelength can decrease the vibration levels by up to 50%, which is comparable to the performance of enormous mass scatters. The dimensions of WIBs must be chosen according to the wavelength of incident waves and the cutoff frequency of the topsoil layer. Considering the significant wavelength of traffic-induced vibration, the use of trench barriers or WIBs becomes impractical and expensive; therefore, mass scatters appear to be an efficient and practical solution.

The Edikan Mine, which consists of Fobinso and Esuajah gold deposits, lies within the Asankrangwa Gold Belt of the Birimian Supergroup in the Kumasi Basin. The metasedimentary rocks in the Basins and the faulted metavolcanic rocks in the Belts that make up the Birimian Supergroup were intruded by granitoids during the Eburnean Orogeny. This research aims to classify granitoids in the Edikan Mine and ascertain the petrogenetic and geochemical characteristics of some auriferous granitoids in the wider Kumasi Basin, Ghana, to understand the implications for geodynamic settings. A multi-methods approach involving field studies, petrographic studies, and whole-rock geochemical analysis was used to achieve the goal of the study. Petrographic studies revealed a relatively high abundance of plagioclase and a low percentage of K-feldspars (anorthoclase and orthoclase) in the Fobinso samples, suggesting that the samples are granodioritic in nature, while the Esuajah samples showed relatively low plagioclase abundance and a high percentage in K-feldspars, indicating that they are granitic. The granitoids from the study areas are co-magmatic. The granitoids in Esuajah and Fobinso are generally enriched in large ion lithophile elements and light rare earth elements than high field strength elements, middle rare earth elements, and heavy rare earth elements, indicating mixing with crustal sources during the evolution of the granitoids. The granitoids were tectonically formed in a syn-collisional+VAG setting, which implies that they were formed in the subduction zone setting. Fobinso granodiorites showed S-type signatures with evidence of extensive crustal contamination, while the Esuajah granites showed I-type signatures with little or no crustal contamination and are peraluminous. Gold mineralization in the study area is structurally and lithologically controlled with shear zones, faulting, and veining as the principal structures controlling the mineralization. The late-stage vein, V3, in the Edikan Mine is characterized by a low vein angle and is mineralized.

Rock is geometrically and mechanically multiscale in nature, and the traditional phenomenological laws at the macroscale cannot render a quantitative relationship between microscopic damage of rocks and overall rock structural degradation. This may lead to problems in the evaluation of rock structure stability and safe life. Multiscale numerical modeling is regarded as an effective way to gain insight into factors affecting rock properties from a cross-scale view. This study compiles the history of theoretical developments and numerical techniques related to rock multiscale issues according to different modeling architectures, that is, the homogenization theory, the hierarchical approach, and the concurrent approach. For these approaches, their benefits, drawbacks, and application scope are underlined. Despite the considerable attempts that have been made, some key issues still result in multiple challenges. Therefore, this study points out the perspectives of rock multiscale issues so as to provide a research direction for the future. The review results show that, in addition to numerical techniques, for example, high-performance computing, more attention should be paid to the development of an advanced constitutive model with consideration of fine geometrical descriptions of rock to facilitate solutions to multiscale problems in rock mechanics and rock engineering.

Various defects exist in natural rock masses, with filled joints being a vital factor complicating both the mechanical characteristics and seepage mechanisms of the rock mass. Filled jointed rocks usually show mechanical properties that are weaker than those of intact rocks but stronger than those of rocks with fractures. The shape of the rock, filling material, prefabricated fissure geometry, fissure roughness, fissure inclination angle, and other factors mainly influence the mechanical and seepage properties. This paper systematically reviews the research progress and findings on filled rock joints, focusing on three key aspects: mechanical properties, seepage properties, and flow properties under mechanical response. First, the study emphasizes the effects of prefabricated defects (shape, size, filling material, inclination angle, and other factors) on the mechanical properties of the rock. The fracture extension behavior of rock masses is revealed by the stress state of rocks with filled joints under uniaxial compression, using advanced auxiliary test techniques. Second, the seepage properties of rocks with filled joints are discussed and summarized through theoretical analysis, experimental research, and numerical simulations, focusing on organizing the seepage equations of these rocks. The study also considers the form of failure under stress–seepage coupling for both fully filled and partially filled fissured rocks. Finally, the limitations in the current research on the rock with filled joints are pointed out. It is emphasized that the specimens should more closely resemble real conditions, the analysis of mechanical indexes should be multi-parameterized, the construction of the seepage model should be refined, and the engineering coupling application should be multi-field–multiphase.

The Maoping lead–zinc mining area is a significant metal mine site in northeastern Yunnan. In this study, both hydraulic fracturing in situ stress testing and ultrasonic imaging logging were first carried out in the mining area. Second, 930 focal mechanism solutions and 231 sets of stress data near the mining area were collected. Then, the variations in the type of in situ stress field, the magnitude of in situ stress, the direction of horizontal principal stress, and the ratio of lateral pressure were analyzed to characterize the distribution of the in situ stress field. On this basis, a new method using borehole breakouts and drilling-induced fractures was proposed to determine the stress direction. Finally, the evolution of the mechanical properties of dolomite with burial depth was analyzed and the influence of rock mechanical properties on the distributions of the in situ stress field was explored. The results show that the in situ stress in the mining area is σ_H > σ_V > σ_h, indicating a strike–slip stress state. The in situ stress is high in magnitude, and its value increases with burial depth. The maximum and minimum horizontal lateral stress coefficients are stabilized at approximately 1.22 and 0.73, respectively. The direction of the maximum horizontal principal stress is NW, mainly ranging from N58.44° W to N59.70° W. The stress field inferred from the focal mechanism solution is in good agreement with the test results. The proportion of structural planes with dip angles between 30° and 75° exceeds 80%, and the dip direction of the structural planes is mainly NW to NWW. The line density of structural planes shows high density in shallow areas and low density in deep areas. More energy tends to be accumulated in rocks with higher elastic modulus and strength, leading to higher in situ stress levels. These findings are of significant reference for mine tunnel layout, support design optimization, and disaster prevention.

This research presents the square root sum of squares response of displacements and tunnel moments under the Kobe and Loma Prieta seismic excitations with a peak ground acceleration of 0.05 g for various dry relative densities of local sand in Bangladesh. For this reason, a one-dimensional gravitational shake table test was performed after calibration to determine the seismic performance of the concrete tunnel–sand–pile interaction model. A vertical 40 kg load was applied on each pile cap along with the seismic excitations. The experimental results obtained were compared with the previous numerical study conducted by using field data so as to better interpret the variations of results. In the case of vertical sand displacement, the ratio between the previous field data obtained through numerical study and the present study is found to be 0.96. Moreover, the experimental results were compared with the 3D full-scale numerical analysis results of Plaxis considering the Mohr–Coulomb constitutive model of sand. Variations of experimental and numerical results show a satisfactory level of alignment with the previously published work. According to the shake table test results, the lateral displacement of the tunnel is greater than the vertical displacement because of the transverse directional seismic excitation on the tunnel body. The minimum difference between lateral and vertical displacements of the tunnel is found to be 31% for a relative density of 27% under the Loma Prieta earthquake. However, this research may be advanced in the future by considering various peak ground accelerations, tunnel–pile clearance, and geometric properties.

Artificial intelligence (AI) has become increasingly important in geothermal exploration, significantly improving the efficiency of resource identification. This review examines current AI applications, focusing on the algorithms used, the challenges addressed, and the opportunities created. In addition, the review highlights the growth of machine learning applications in geothermal exploration over the past decade, demonstrating how AI has improved the analysis of subsurface data to identify potential resources. AI techniques such as neural networks, support vector machines, and decision trees are used to estimate subsurface temperatures, predict rock and fluid properties, and identify optimal drilling locations. In particular, neural networks are the most widely used technique, further contributing to improved exploration efficiency. However, the widespread adoption of AI in geothermal exploration is hindered by challenges, such as data accessibility, data quality, and the need for tailored data science training for industry professionals. Furthermore, the review emphasizes the importance of data engineering methodologies, data scaling, and standardization to enable the development of accurate and generalizable AI models for geothermal exploration. It is concluded that the integration of AI into geothermal exploration holds great promise for accelerating the development of geothermal energy resources. By effectively addressing key challenges and leveraging AI technologies, the geothermal industry can unlock cost-effective and sustainable power generation opportunities.

In order to mitigate the risk of geological disasters induced by fault activation when roadways intersect reverse faults in coal mining, this paper uses a combination of mechanical models with PFC^2D software. A mechanical model is introduced to represent various fault angles, followed by a series of PFC^2D loading and unloading tests to validate the model and investigate fault instability and crack propagation under different excavation rates and angles. The results show that (1) the theoretical fault model, impacted by roadway advancing, shows a linear reduction in horizontal stress at a rate of −2.01 MPa/m, while vertical stress increases linearly at 4.02 MPa/m. (2) At field excavation speeds of 2.4, 4.8, 7.2, and 9.6 m/day, the vertical loading rates for the model are 2.23, 4.47, 6.70, and 8.93 Pa/s, respectively. (3) Roadway advancement primarily causes tensile-compressive failures in front of the roadway, with a decrease in tensile cracks as the stress rate increases. (4) An increase in the fault angle leads to denser cracking on the fault plane, with negligible cracking near the fault itself. The dominant crack orientation is approximately 90°, aligned with the vertical stress.

Microcrack growth during progressive compressive failure in brittle rocks strongly influences the safety of deep underground engineering. The external shear stress τ_xy on brittle rocks greatly affects microcrack growth and progressive failure. However, the theoretical mechanism of the growth direction evolution of the newly generated wing crack during progressive failure has rarely been studied. A novel analytical method is proposed to evaluate the shear stress effect on the progressive compressive failure and microcrack growth direction in brittle rocks. This model consists of the wing crack growth model under the principal compressive stresses, the direction correlation of the general stress, the principal stress and the initial microcrack inclination, and the relationship between the wing crack length and strain. The shear stress effect on the relationship between y-direction stress and wing crack growth and the relationship between y-direction stress and y-direction strain are analyzed. The shear stress effect on the wing crack growth direction during the progressive compressive failure is determined. The initial crack angle effect on the y-direction peak stress and the wing crack growth direction during the progressive compressive failure considering shear stress is also discussed. A crucial conclusion is that the direction of wing crack growth has a U-shaped variation with the growth of the wing crack. The rationality of the analytical results is verified by an experiment and from numerical results. The study results provide theoretical support for the evaluation of the safety and stability of surrounding rocks in deep underground engineering.