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During the process of developing and utilizing geothermal resources, various challenges are encountered. One such challenge is the decrease in temperature and pressure of the geothermal reservoir as a result of the increasing geothermal exploitation and duration. In addition, the discharge of geothermal tail water poses a risk of thermal pollution, leading to environmental concerns. To address these issues effectively, reinjection of geothermal fluids into the reservoir can be implemented as a viable solution. Prior to initiating the geothermal development and utilization, it is crucial to conduct scientifical and rational planning of the layout of production and reinjection wells. This involves exploring optimal strategies for the production-reinjection scheme that prevents the premature thermal breakthrough and maximize the efficient utilization of geothermal resources, thereby extending the lifespan of the geothermal reservoir. The Fengpei Basin, a Cenozoic rift basin that developed since the Paleogene period, exhibits a widespread distribution of geothermal reservoirs, primarily composed of the Ordovician limestone with karst and fracture characteristics. Building upon the geothermal resource exploration results in the Anguo Town in Peixian County in Jiangsu Province, this study utilizes key parameters obtained from pumping tests and reinjection experiments, such as well spacing and the reinjection-to-production ratio. This paper establishes a 3D coupled numerical model of geothermal water seepage and heat transfer by using the Feflow6.2 software. The recoverable reserves of geothermal fluid within the geothermal reservoir are simulated and predictd, specifically the Ordovician limestone formation. Furthermore, a simulated optimization of the development and utilization scheme for the production-reinjection wells is conducted. The results reveal that an appropriate well spacing of 389 m between the producing well (RPX01) and the reinjection well (RPX02) is recommended. Moreover, the reinjection-to-production ratio, namely the ratio of average aquifer hydraulic conductivity, is determined to be 1.29, supporting a sustainable approach of one-for-one pumping and reinjection. With a stabilized drawdown of 50.61 m, the production well has a capacity to recover 1000 m3/d of geothermal resources. Under the conditions of a production rate and a reinjection rate of 1000 m3/d, as well as a reinjection temperature of 40 °C, the simulation predicts a decrease in groundwater level by 45.49 m and a temperature reduction of 1.44 °C after ten heating seasons. This represents the optimal cyclic development and utilization scheme among the simulated scenarios. The above results provide a scientific basis for decision-making in the construction of the clean energy heating demonstration area in rural northern Jiangsu. They contribute to the establishment of a scientifically sound and sustainable approach for utilizing geothermal resources, while considering the challenges associated with the thermal breakthrough and the environmental impact of geothermal tail water discharge.

Prediction of water inflow of a sub-sea tunnel under the blasting vibration effect is still a difficult subject. This paper takes the sub-sea tunnel between the Wawuzhuang Station and Guizhou Road Station of the Qingdao Metro Line 1 as the engineering background. Based on the equivalent continuum model, the mirror image method is used to deduce the calculation formula for the water inflow of the sub-sea tunnel considering the damage area factor. Through forward modeling and inversion, combined with numerical simulation results and actual engineering monitoring results, the correctness of the formula is comprehensively verified, and the influence mechanism of damage area factors on water inflow is analyzed. The results show that the squeezing effect caused by blasting vibration makes the pore water pressure of surrounding rock around the tunnel rise rapidly in a short time. After reaching the peak value, it began to decline slowly with the weakening and disappearance of blasting vibration. Under the influence of damage zone factors, the water inflow of the tunnel increases gradually with the increasing thickness of the damage zone, but it will not increase continuously with the increase of the coefficient of permeability in the damaged area. Through numerical simulation calculation, the ratio of tunnel water inflow considering blasting damage area is 1.4, and the error is only 4.1% compared with the calculation result of 1.342 deduced in this paper. The calculated results in this study are only 0.53 m3/(d·m) less than the field measured results, and are closer to the measured results than those with the traditional calculation formula, indicating that the calculation formula in this paper is suitable for the calculation of tunnel water inflow considering the factor of damage zone, and are of high engineering application value.

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Purposes As a result of the ongoing replenishment of groundwater, a multifaceted system for the storage and circulation of groundwater has developed within overlying goaf and roadway. Coal mines encounter technical challenges in preventing and managing water damage in the roof goaf during the process of multiple coal seam composite mining, leading to a substantial requirement for daily roof water exploration and drainage engineering. Methods This paper focuses on the roof and floor rocks of coal seams as the subject of investigation. The study aims to analyze the fracture zone development between coal seams in the context of multiple seams mining, utilizing on-site electrical testing, numerical simulation, and theoretical analysis. Findings The findings of the experimental investigation indicate that the extraction of coal seams in close proximity facilitates the full interconnection of the goafs, resulting in the formation of a water accumulation zone composed of double coal seam goafs. The depth of the damage zone caused by the disturbance of the double coal seam floor is measured at 15.6 m. As the underlying working face is mined, the numbers of weak structural planes in the surrounding rock increas, leading to an expansion of the area of resistivity increase. Upon reaching a height of 58 m, the development of fracture zone gradually ceases. Optimal exploration and drainage of the roof empty water can be achieved to the fullest extent when the effective thickness of the key water barrier layer is no less than 20 m. Conclusions The concept of goaf water hazard prevention and coal mining under water-containing based on the coal seam spacing and key water-resisting layer is proposed. The conception of “finding out the structure, controlling the seam spacing, and mining after upper preventing” should be followed. The research results not only effectively prevent and control the threat of water inrush from the roof goaf, but also reduce the workload and production cost of water exploration and drainage in future. It can also provide reference for water-retaining mining technology in multiple coal seams affected by the water hazard in the roof goaf.

Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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[Introduction] With the development of wind power generation technology, the unit capacity of permanent magnet wind generator is increasing, and the heating power is also increasing. The heat dissipation of generator is facing unprecedented challenges. How to effectively solve the problem of generator temperature rise and heat dissipation difficulty has been the focus of our study. [Method] Based on the STAR-CCM+ software platform, an integrated numerical simulation method for generator heat dissipation and cooling was proposed in this paper. The reliability of the numerical calculation method was verified by comparing the calculated values with the experimental values. On this basis, a study was conducted on the internal temperature distribution law and the factors influencing the cooling system heat dissipation performance of the high power permanent magnet wind generator. [Result] Under the rated power, the highest temperature of the winding and stator core appear in the middle area. If the process conditions allow, the cooling water pipe should be as close to the winding as possible to take away more heat. The stator core temperature and winding temperature can be reduced significantly by increasing the total intake air volume of the generator. The intake air temperature has a linear relationship with the maximum temperature of the winding and stator core. For every 5℃ decrease in the intake air temperature, the maximum temperature will be reduced by about 1.4℃. Reducing the intake air temperature can improve the heat dissipation performance of the generator to a certain extent. The intake water temperature has a linear relationship with the maximum temperature of the winding and stator core. For every 5℃ decrease in the intake water temperature, the maximum temperature will be reduced by about 3.3℃. Reducing the intake water temperature can greatly improve the heat dissipation performance of the generator. In addition, the gap between the cooling water pipe and the stator core greatly hinders the heat transfer of the cooling water pipe. Filling the gap with materials with good thermal conductivity can effectively improve the heat dissipation performance of the generator. [Conclusion] The conclusions drawn in this paper can effectively guide the heat dissipation design of permanent magnet wind generator and ensure the safe operation of wind turbines in normal work.

Objective Monitoring natural attenuation (MNA) is a widely used, economical and effective remediation technique for soil and groundwater contamination. The migration of nonaqueous phase liquid (NAPL) in heterogeneous strata is an important element in the assessment for the efficiency of MNA. Methods Based on three consecutive years of dynamic groundwater quality monitoring data, the purpose of this study is to accurately characterize the biodegradation processes of multiphase fluids at a typical phenol contaminated site in northern China. A multiphase flow numerical model of phenol transport considering Monod biodegradation processes based on TOUGH3/TMVOCBio software was developed and applied. The model depicted the spatial distribution and temporal variation of phenol under the current conditions well and analysed the sensitivities of the adsorption and biodegradation parameters. The paper also discussed the removal contributions of dissolution, volatilization, adsorption and biodegradation effects under uncertainty of adsorption and microbial degradation parameters and predicted two different natural attenuation scenarios for source disposal. Results The contribution of phenol removal varies over a range under the influence of parameter uncertainty, with 17.91% to 58.02% for biodegradation, and precipitation conditions affect the seasonal variation in phenol concentrations. In the future 20 years, under the conditions with complete removal of the phenol source and the present leakage model, the total mass removal rate of phenol will arrive at 98% and 80% at the end of the 20th year, respectively. Conclusion This paper identifies the biodegradation parameters with high sensitivity in the multiphase flow model, which provides a reference for the numerical simulation of the organic matter biodegradation process at petrochemical sites and can also provide a theoretical basis for the application of MNA technology in China.

Sgnificance To quantitatively study the impact of various nonlinear factors in the coastal zone on groundwater flow and solute transport processes, MARUN (Marine Unsaturated) software for simulating groundwater flow in the coastal zone was developed. Progress This paper reviews the research and application progress of MARUN from the aspects of model principles, algorithm characteristics, literature review, and case analyses. The software is suitable for numerical simulations of two-dimensional vertical profiles of groundwater flow and solute transport reactions in the coastal zone. MARUN implements a finite element algorithm for variable saturation and density flow and solute transport, mass-consistent implicit difference discretization, and Picard, Newton, and Newton-Picard numerical solution methods, covering many nonlinear factors such as tides, waves, evaporation, rainfall, and load effects. It is characterized by its high professionalism, good flexibility, and high fault tolerance, but it does not have a graphical user interface. MARUN has achieved a number of highlighted research results in scenarios such as bioremediation of crude oil pollution on beaches, seawater-groundwater circulation processes in shallow aquifers in intertidal zones, and the evolution of regional groundwater flow systems. Conclusion and Prospects In the future, MARUN needs to be further expanded into three-dimensional space and coupled with physicochemical processes with random characteristics to improve its performance level of simulating groundwater flow and solute transport in coastal aquifers.

Objective The Kuncheng Tunnel of the Central Yunnan Water Diversion Project crosses the Heilongtan and Bailongtan areas, the major headwater regions in the Chenggong District of Kunming City. Methods Tunnel water inrush may seriously threaten the safety of the urban water supply. In this paper, based on hydrodynamic data and hydrochemical data during tunnel construction, the characteristics of the karst water system, the origin of the springs, and the impact of tunnel construction were analysed. Then, a three-dimensional groundwater flow model for the Heilongtan-Bailongtan Section was developed and calibrated to simulate and predict groundwater level changes during the construction of the Kuncheng Tunnel, and the water environment effect of tunnel construction was evaluated. Results The results show that both the Heilongtan and Bailongtan springs are mainly recharged by the same karst P1q+m aquifer. However, controlled by aquitard P1d and the Hunshuitang fault downstream of the Sanjiacun Depression, the two springs actually belong to two relatively independent karst water systems. In addition, the excavation of the Kuncheng Tunnel has changed the regional groundwater flow field and cut off the flow of Bailongtan, while it has negligible impact on Heilongtan. Conclusion This study discusses the genetic relationship of karst spring, and quantitatively analyzes the impact of tunnel excavation on water environment, which has reference significance for preventing water inrush in tunnel construction.

Objective Monitoring natural attenuation (MNA), as a low cost remediation method for groundwater pollution that does not produce secondary pollutants and has little impact on the polluted site environment, has high application value and development prospects, and is worth practicing and studying. Methods This paper adopts a groundwater-contaminated site in Baiyun District of Guangzhou to assess the applicability of MNA. Based on the analysis of hydrogeological conditions and pollution status, a groundwater numerical simulation program MODFLOW was used to establish a groundwater flow model for contaminated sites. The pollutant migration numerical simulation program MT3DMS was used to establish a pollutant migration model for the site. The migration processes of groundwater flow, main pollutants total petroleum hydrocarbons (TPH), and heavy metal nickel (Ni) were simulated, respectively. Based on the model, the performances of the MNA alone and the MNA combined with pump and treat methods were compared. Results The results show that TPH and Ni are both sensitive to changes in the Freundlich constant and Freundlich exponent. The TPH shows good natural attenuation effect and can be substantially attenuated by the MNA alone. The concentration of TPH decreased from the initial value of 1.52 mg/L to the target (0.3 mg/L) after 850 days. Ni decay is relatively slow and it is suitable to adopt to a natural attenuation scheme under monitoring combined with the pump & treat method. The concentration of Ni decreased from the initial value of 0.13 mg/L to the target (0.02 mg/L) after 300 days. For a contaminated site with large natural attenuation capacities and/or low groundwater flow velocities, MNA alone is an appropriate remediation strategy. In contrast, for a contaminated site with low natural attenuation capacities and/or high groundwater flow velocities, the MNA combined with pump and treat may be a better remediation strategy. Conclusion This study provides an appropriate reference for the application of MNA to groundwater pollution remediation.

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Restricted by the surface smoothness and topography, it is impossible for some high-speed railways on mountainous regions to avoid parts of rockfall development sections, posing great safety challenges to construction projects and railway operations. In light of that, this paper laid its focus on the rockfall situated by the entrance of Xinghuayu Tunnel along the proposed Jinan-Zaozhuang Railway project, and leveraged the power of drone-captured 3D aerial photography to perform digital geological survey and mapping so as to accurately identify the development characteristics, scale, as well as modes of deformation and failure of said rockfall. Next, by cross-referencing the results of 3DEC numerical simulation with those from analytic hierarchy process (AHP), color-coded maps highlighting the scope of influence and danger levels of potential rockfalls induced were obtained. Using said maps, zone-by-zone hazard and risk assessment were then performed, based on which corresponding prevention and control measures were put forward. The findings show that among the 12 dangerous rock belts identified from the drone-captured 3D aerial photography model, only Belt No. 5 would threaten the safety of the tunnel entrance and bridge abutments, for which the combination of anti-rockfall passive protective netting and an open-cut tunnel structure was recommended as a comprehensive solution. By virtue of the solution's effectiveness, this study can offer reliable references for not only zone-by-zone hazard and risk assessment for rockfalls, but also railway route selection and disaster prevention and mitigation. [ABSTRACT FROM AUTHOR]

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Numerical simulation and related experimental research on supersonic aerodynamic heating are important contents in the development of hypersonic vehicles. The boundary layer flow and heat transfer process in the supersonic aerodynamic heating phenomenon are analyzed, and the effects of the engineering model, gas model, turbulence model, grid scale, calculation scheme, and boundary conditions in aerodynamic heating simulation on the numerical simulation are discussed from the physical point of view. This paper introduces the test equipments commonly used in the research of aerodynamic heating, such as oxygebacetylene flame ablation, radiation heater and high enthalpy wind tunnel, and their advantages and disadvantages, also discusses the similar parameters in the ground simulation test, and points out the reasons for the over high heat flow of the cold wall.

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Fenders play an important protective role in ship collisions, but there are few studies related to the collision simulation methods and the protection mechanism of composite fenders. First, aimed at the new composite fender design scheme proposed in this paper and based on the material properties exhibited in the test, low-density foam and hyperelastic models are selected to simulate the inner foam and outer polyurethane of the fender, respectively. Subsequently, for the hull-fender-quay collision problem, a multi-body geometry model is established and a collision simulation method is formed to analyze the fender protection mechanism from the perspective of energy conversion. It is proved that the composite material has a better protection effect on the hull structure than the rubber fender. Finally, the inner foam strength, hull stiffness, outer polyurethane thickness, and tensile strength of composite materials are varied to analyze the protection mechanism of composite materials respectively. The results show that the relative stiffness of the fender and the structure is the main factor affecting the protection performance. The inner foam of the composite fender is the main energy-absorbing structure, absorbing the kinetic energy of the hull through compression deformation to reduce the response of the structure, while the outer polyurethane mainly plays the role of protecting the core.

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Restricted by the surface smoothness and topography, it is impossible for some high-speed railways on mountainous regions to avoid parts of rockfall development sections, posing great safety challenges to construction projects and railway operations. In light of that, this paper laid its focus on the rockfall situated by the entrance of Xinghuayu Tunnel along the proposed Jinan-Zaozhuang Railway project, and leveraged the power of drone-captured 3D aerial photography to perform digital geological survey and mapping so as to accurately identify the development characteristics, scale, as well as modes of deformation and failure of said rockfall. Next, by cross-referencing the results of 3DEC numerical simulation with those from analytic hierarchy process (AHP), color-coded maps highlighting the scope of influence and danger levels of potential rockfalls induced were obtained. Using said maps, zone-by-zone hazard and risk assessment were then performed, based on which corresponding prevention and control measures were put forward. The findings show that among the 12 dangerous rock belts identified from the drone-captured 3D aerial photography model, only Belt No. 5 would threaten the safety of the tunnel entrance and bridge abutments, for which the combination of anti-rockfall passive protective netting and an open-cut tunnel structure was recommended as a comprehensive solution. By virtue of the solution’s effectiveness, this study can offer reliable references for not only zone-by-zone hazard and risk assessment for rockfalls, but also railway route selection and disaster prevention and mitigation.

The study of the transient electromagnetic detection device with small sized coil and easy installation underground will offer new insights into the real-time dynamic exploration and forecast water-bearing structure in excavation roadway.By drawing on the full-space transient electromagnetic theory, this paper adopted the three-dimensional time-domain finite element method for numerical simulation to explore the characteristics of the secondary field response obtained by small coil excitation and the transient electromagnetic response received by the magnetic core coil.This study constructed a geological-geophysical model of the water-bearing fault in front of the roadway excavation working face, studied the transient electromagnetic response characteristics of the small coil device for the water-bearing fault, and compared the effects of small coil and conventional coil in advance detection.The study shows that : ①the decay law of the induced electric potential generated by the small coil source excitation is the same as that of the induced electric potential generated by the conventional transmitting coil with time, ②the magnetic core coil can effectively improve the induced signal strength, ③the application of both the small coil device and the conventional coil device can effectively explain the distribution range of the low resistance area, ④the detection results match the verification results of the roadway excavation.Combined with the underground field test, this paper verified the applicability and effectiveness of the small coil device applied to mine transient electromagnetic method advance detection.

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Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)