Deep Underground Science and Engineering最新文献

It is important to study the effect of hydrate production on the physical and mechanical properties of low-permeability clayey–silty reservoirs for the large-scale exploitation of hydrate reservoirs in the South China Sea. In this study, a multiphysical-field coupling model, combined with actual exploration drilling data and the mechanical experimental data of hydrate cores in the laboratory, was established to investigate the physical and mechanical properties of low-permeability reservoirs with different slope angles during 5-year hydrate production by the depressurization method via a horizontal well. The result shows that the permeability of reservoirs severely affects gas production rate, and the maximum gas production amount of a 20-m-long horizontal well can reach 186.8 m³/day during the 5-year hydrate production. Reservoirs with smaller slope angles show higher gas production rates. The depressurization propagation and hydrate dissociation mainly develop along the direction parallel to the slope. Besides, the mean effective stress of reservoirs is concentrated in the near-wellbore area with the on-going hydrate production, and gradually decreases with the increase of the slope angle. Different from the effective stress distribution law, the total reservoir settlement amount first decreases and then increases with the increase of the slope angle. The maximum settlement of reservoirs with a 0° slope angle is up to 3.4 m, and the displacement in the near-wellbore area is as high as 2.2 m after 5 years of hydrate production. It is concluded that the pore pressure drop region of low-permeability reservoirs in the South China Sea is limited, and various slope angles further lead to differences in effective stress and strain of reservoirs during hydrate production, resulting in severe uneven settlement of reservoirs.

Gas storage in abandoned mines is one way to reuse waste space resources. The surrounding rock of gas storage reservoirs in underground roadways undergoes damage and deformation under the cyclic loading of gas charging and discharging, which can pose a risk to the safety of the reservoirs. This study establishes a true triaxial numerical model of rock mass with the discrete element method (DEM) and explores the crack evolution of surrounding rock of underground gas storage during cyclic loading and unloading. Also, a damage evolution model in numerical analysis considering residual deformation is developed to explain the experimental results. As was revealed, cyclic loading and unloading resulted in fatigue damage in the specimen and caused strength deterioration of the specimen. During the loading process, the uniformly distributed force chains of the rock mass redistributed, evolving gradually to mostly transverse force chains. This contributed to the appearance of blank areas in the force chains when through cracks appear. The ratio of tensile cracks to shear cracks gradually decreases and finally stabilizes at 7:1. The damage evolution model considering residual strain can be mutually verified with the numerical simulation results. Based on the DEM model, it was found that there was a certain threshold of confining pressure. When the confining pressure exceeded 30 MPa, the deformation to ductility of sandstone samples began to accelerate, with a greater residual strength. This study provides a theoretical basis for analyzing the long-term mechanical behavior of surrounding rock of gas storage in abandoned mines.

The Shenzhen–Zhongshan Bridge is a 24-km-long bridge and tunnel system, including a 6.8-km-long super cross section subsea tunnel. To solve the smoke exhaust problem of a super large cross-section subsea tunnel, the tunnel has a new smoke exhaust system that combines a horizontal smoke exhaust cross section at the top and sidewall smoke exhaust holes. In order to evaluate the potential fire hazards of this type of tunnel, a 1:30 tunnel model was established and 140 small-scale experiments on underwater tunnel fires were conducted. By changing the fire power, fire location, and fan operation mode, different scenarios of submarine immersed tunnel fire were simulated and the related key parameters such as fire smoke diffusion behavior and smoke temperature distribution were studied. On this basis, the optimal smoke control strategy was proposed for different fire scenarios. The research results indicate that the new smoke exhaust system can fully utilize the smoke flow characteristics, significantly improve smoke exhaust efficiency, and increase available evacuation time, thus further enhancing the fire safety of super large cross-section subsea tunnels.

This issue covers the papers on two special themes: (1) Mineral resources from deep sea—Science and Engineering and (2) Planning and development of underground space and infrastructure for sustainable and liveable cities.

The special theme of “Mineral resources from deep sea—Science and Engineering” is on the exploration and transport of mineral resources from deep sea. The mineral resources are rich in deep sea and their rational development and utilization can meet the needs of social and economic development. The security and strategy of deep-sea mineral resource exploration are important to the successful development of high-quality marine economy. However, deep-sea science and mineral resource exploitations confront many unknowns. This special theme aims to provide a platform for the exploration and exchange in research and engineering progresses and six papers were received, including four Original Research Papers, one Review Paper, and one Short Communication. The authors are from Australian Catholic University, National University of Singapore, Ocean University of China, China University of Mining and Technology, and so on.

The idea for this special theme originates from the First Young Scholars Symposium on Deep-Sea Science and Mineral Resources (2022). Deep Underground Science and Engineering (DUSE) collaborated with the conference organizer and launched a call for a special theme: Mineral Resources from Deep Sea—Science and Engineering. Guest Editors of this special theme are Prof. Jianhua Yue (China University of Mining and Technology), Prof. Yonggang Jia (Ocean University of China), Prof. Chunhui Tao (Second Institute of Oceanography, Ministry of Natural Resources, China), Prof. Haiyan Yang (China University of Mining and Technology), Prof. Honglei Shen (China University of Mining and Technology), and Prof. Zhuangcai Tian (China University of Mining and Technology).

The special theme of “Planning and development of underground space and infrastructure for sustainable and liveable cities” is on city development from the prospects of underground space and infrastructure. The utilization of urban underground space for accommodating urban functions, through developing underground commercial, transport, and public infrastructure, has been a common practice in urban development in past decades. Increased migration of populations to cities brings many urbanization problems, such as inadequate land and infrastructure, air and noise pollution, traffic congestion, and degraded environmental quality, thus providing an opportunity for underground infrastructure as an attractive solution to these problems. As a relatively new dimension of cities, underground space has been widely recognized as a valuable resource for city development. Urban underground space utilization is an effective way of developing and redesigning cities, promoting sustainable urban development, and building liveable cities. Underground infrastruc

This study delves into the latest advancements in machine learning and deep learning applications in geothermal resource development, extending the analysis up to 2024. It focuses on artificial intelligence's transformative role in the geothermal industry, analyzing recent literature from Scopus and Google Scholar to identify emerging trends, challenges, and future opportunities. The results reveal a marked increase in artificial intelligence (AI) applications, particularly in reservoir engineering, with significant advancements observed post-2019. This study highlights AI's potential in enhancing drilling and exploration, emphasizing the integration of detailed case studies and practical applications. It also underscores the importance of ongoing research and tailored AI applications, in light of the rapid technological advancements and future trends in the field.

Meeting the climate change mitigation targets will require a substantial shift from fossil to clean fuels in the heating sector. Heat pumps with deep borehole exchangers are a promising solution to reduce emissions. Here the thermal behavior of deep borehole exchangers (DBHEs) ranging from 1 to 2 km was analyzed for various heat flow profiles. A strong correlation between thermal energy extraction and power output from DBHEs was found, also influenced by the heating profile employed. Longer operating time over the year typically resulted in higher energy production, while shorter one yielded higher average thermal power output, highlighting the importance of the choice of heating strategy and system design for optimal performance of DBHEs. Short breaks in operation for regenerating the borehole, for example, with waste heat, proved to be favorable for the performance yielding an overall heat output close to the same as with continuous extraction of heat. The results demonstrate the usefulness of deep boreholes for dense urban areas with less available space. As the heat production from a single DBHE in Finnish conditions ranges from half up to even a few GWh a year, the technology is best suitable for larger heat loads.

As the first gold mine discovered at the sea in China and the only coastal gold mine currently mined there, Sanshandao Gold Mine faces unique challenges. The mine's safety is under continual threat from its faulted structure coupled with the overlying water. As the mining proceeds deeper, the risk of water inrush increases. The mine's maximum water yield reaches 15 000 m³/day, which is attributable to water channels present in fault zones. Predominantly composed of soil–rock mixtures (SRM), these fault zones' seepage characteristics significantly impact water inrush risk. Consequently, investigating the seepage characteristics of SRM is of paramount importance. However, the existing literature mostly concentrates on a single stress state. Therefore, this study examined the characteristics of the permeability coefficient under three distinct stress states: osmotic, osmotic–uniaxial, and osmotic–triaxial pressure. The SRM samples utilized in this study were extracted from in situ fault zones and then reshaped in the laboratory. In addition, the micromechanical properties of the SRM samples were analyzed using computed tomography scanning. The findings reveal that the permeability coefficient is the highest under osmotic pressure and lowest under osmotic–triaxial pressure. The sensitivity coefficient shows a higher value when the rock block percentage ranges between 30% and 40%, but it falls below 1.0 when this percentage exceeds 50% under no confining pressure. Notably, rock block percentages of 40% and 60% represent the two peak points of the sensitivity coefficient under osmotic–triaxial pressure. However, SRM samples with a 40% rock block percentage consistently show the lowest permeability coefficient under all stress states. This study establishes that a power function can model the relationship between the permeability coefficient and osmotic pressure, while its relationship with axial pressure can be described using an exponential function. These insights are invaluable for developing water inrush prevention and control strategies in mining environments.

Three sandstone specimens common in rock engineering were selected to study the differences in the mechanical properties of rocks with different lithologies. The development and expansion of the internal cracks in the specimens were observed by combining the simulation system with the acoustic emission system. Through the combination of dynamic and static stresses, the deformation and damage of rocks under deep rock excavation and blasting were simulated. As the results show, the acoustic emission events of specimens with different lithologies under combined static and dynamic cyclic loading can be roughly divided into three phases: weakening, stabilizing, and surging periods. In addition, the acoustic emission characteristics of specimens with different lithologies show general consistency in different compression phases. The degree of fragmentation of specimens increases with the applied stress level; therefore, the stress level is one of the important factors influencing the damage pattern of specimens. The acoustic emission system was used to simulate the deformation and damage of rocks subjected to deep rock body excavation and engineering blasting. Cyclic dynamic perturbations under sinusoidal waves with a frequency of 5 Hz, a loading rate of 0.1 mm/min, a cyclic amplitude of 5 MPa, and a loading rate of 0.1 mm/min were applied to the three rock samples during the experiments. Among them, the fine-grained sandstones are the most sensitive to the sinusoidal cyclic perturbation, followed by the muddy siltstone and the medium-grained sandstones. On this basis, the acoustic emission energy release characteristics were analyzed, and the waveform characteristics in the damage evolution of the specimen under dynamic perturbation were studied by extracting the key points and searching for the main frequency eigenvalues.

Geothermal energy extraction often results in the release of naturally occurring carbon dioxide (CO₂) as a byproduct. Research on carbon storage using volcanic rock types other than basalt under both acidic and elevated temperature conditions has been limited so far. Our study uses batch reactor experiments at 100°C to investigate the dissolution of andesite rock samples obtained from an active geothermal reservoir in Sumatra (Indonesia). The samples are subjected to reactions with neutral-pH fluids and acidic fluids, mimicking the geochemical responses upon reinjection of geothermal fluids, either without or with dissolved acidic gases, respectively. Chemical elemental analysis reveals the release of Ca²⁺ ions into the fluids through the dissolution of feldspar. The overall dissolution rate of the rock samples is 2.4 × 10^–11 to 4.2 × 10^–11 mol/(m² · s), based on the Si release during the initial 7 h of the experiment. The dissolution rates are about two orders of magnitude lower than those reported for basaltic rocks under similar reaction conditions. This study offers valuable insights into the potential utilization of andesite reservoirs for effective CO₂ storage via mineralization.

Internal solitary wave (ISW), as a typical marine dynamic process in the deep sea, widely exists in oceans and marginal seas worldwide. The interaction between ISW and the seafloor mainly occurs in the bottom boundary layer. For the seabed boundary layer of the deep sea, ISW is the most important dynamic process. This study analyzed the current status, hotspots, and frontiers of research on the interaction between ISW and the seafloor by CiteSpace. Focusing on the action of ISW on the seabed, such as transformation and reaction, a large amount of research work and results were systematically analyzed and summarized. On this basis, this study analyzed the wave–wave interaction and interaction between ISW and the bedform or slope of the seabed, which provided a new perspective for an in-depth understanding of the interaction between ISW and the seafloor. Finally, the latest research results of the bottom boundary layer and marine engineering stability by ISW were introduced, and the unresolved problems in the current research work were summarized. This study provides a valuable reference for further research on the hazards of ISW to marine engineering geology.