| 1. |
- Chen, Hongyu, et al.
(författare)
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Effects of microbial culture and chicken manure biochar on compost maturity and greenhouse gas emissions during chicken manure composting
- 2020
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Ingår i: Journal of Hazardous Materials. - : Elsevier. - 0304-3894 .- 1873-3336. ; 389
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Tidskriftsartikel (refereegranskat)abstract
- The effects of chicken manure biochar (CMB) and chicken manure integrated microbial consortium (CMMC) as co-amendments were assessed on compost maturity and reduction of greenhouse gases and ammonia (NH3) emissions during chicken manure composting. Composting was conducted using six combinations of CMB and CMCC (0 % CMB + 0 % CMMC, 0 % CMB + 10 % CMMC, 2 % CMB + 10 % CMMC, 4 % CMB + 10 % CMMC, 6 % CMB + 10 % CMMC, 10 % CMB + 10 % CMMC added on a dry weight basis) in six polyvinyl chloride composting reactors for 42 days under an aerobic environment. Co-amendment of CMB and CMMC extended the thermophilic stage and promoted compost maturity. The release of greenhouse gases [nitrous oxide (N2O) and methane (CH4)] and NH3 from treatments co-amended by CMB and CMMC were reduced by 19.0-27.4 %, 9.3-55.9 % and 24.2-56.9 %, respectively, compared with the control. In addition, a redundancy analysis showed that the C/N ratio and temperature had a significant relationship with greenhouse gases and NH3 emissions among all physiochemical characteristics.
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| 2. |
- Duan, Hongyu, et al.
(författare)
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Analysis of cement grout hydraulic erosion in a homogeneous fracture
- 2024
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Ingår i: Tunnelling for a Better Life - Proceedings of the ITA-AITES World Tunnel Congress, WTC 2024. - : CRC Press/Balkema. ; , s. 2522-2528
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Konferensbidrag (refereegranskat)abstract
- Cement grouting has been widely used in rock tunneling to reduce groundwater inflow by sealing rock fractures. However, the injected cement grout often encounters hydraulic erosion that affects the safety and sustainability of rock tunnels in the long term. Analysis of the long-term hydraulic erosion effect on cement grout in rock fractures is therefore important for the safety and sustainability development of rock tunnel engineering. In this work, a hydraulic erosion model for analyzing cement grout erosion in a homogeneous fracture is established and used to theoretically investigate the transmissivity evolution of the grouted fracture under longterm hydraulic erosion. In the present model, the fracture seepage characteristics, solid erosion theory and mass conversation for water-solid two-phase flow are considered, and the mathematical model as a set of partial differential equations is established. Based on laboratory tests, the key parameters (e.g., erosion coefficient) are calibrated and the erosion model is validated. Numerical simulations are conducted by numerically resolving the mathematical model. The results show that the erosion phenomenon first occurs in the edge areas of the grouted area near the fracture boundary; the erosion area gradually expands toward the center of the grouted area. The porosity and flow velocity significantly increase in the area with relatively strong erosion effects. During the erosion process, the concentration of cement grout gradually increases along the seepage path until a more uniform distribution of cement particle concentration is achieved. Due to the erosion process, the spatial distribution of hydraulic pressure along the fracture direction transforms from a linear distribution to a nonlinear distribution. The effective fracture transmissivity increases nonlinearly along the erosion process. The presented erosion model and analysis results are potentially useful for the safety and durability assessment of rock tunnels.
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| 3. |
- Duan, Hongyu, et al.
(författare)
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Co-exploitation of coal and geothermal energy through water-conducting structures : Improving extraction efficiency of geothermal well
- 2024
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Ingår i: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 228
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Tidskriftsartikel (refereegranskat)abstract
- Co-exploitation of coal and geothermal energy through water-conducting structures is one of the most promising methods for harnessing renewable energy in some coal mines. A rock compression-erosion coupling test system is built to investigate the extraction efficiency of geothermal wells in the co-exploitation scheme. Compression-erosion tests are carried out to analyze the evolution of mechanics and hydraulic characteristics of broken rocks. The testing results show that the hydrothermal flow erodes the fine rock particles, and compressive deformation can be observed during the erosion process. The erosion effect in broken rocks intensifies with the decrease of axial stress and the increase of fractal dimension, water pressure, and inner radius. Meanwhile, the rock sample shows more significant deformation. Two permeability forecasting models are adopted to forecast permeability evolution during geothermal extraction. The forecasting results indicate that the Brinkman model is better than the Hazen model, and the accuracy of the Brinkman model is lower for the samples with stronger compression-erosion effects. In addition, strategies to improve the extraction efficiency are proposed, i.e., reinforcing the broken rocks above the geothermal well, locating geothermal wells in rocks with higher fragmentation, increasing pumping pressure, and expanding the geothermal well size.
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| 4. |
- Duan, Hongyu, et al.
(författare)
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Sensitivity analysis of hydraulic erosion and calibration of the erosion coefficient
- 2024
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Ingår i: Engineering Geology. - : Elsevier BV. - 0013-7952 .- 1872-6917. ; 338
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Tidskriftsartikel (refereegranskat)abstract
- Hydraulic erosion may pose a threat to the safety and sustainability of geo-related infrastructure, yet quantifying the intricate process of hydraulic erosion still poses a significant scientific and technical challenge. One important step in meeting this challenge is the formulation of a hydraulic erosion model with the erosion coefficient as a central controlling parameter. Calibration of the erosion coefficient (or rate) remains one of the main obstacles to improving predictive modelling, particularly in scenarios lacking long-term laboratory test data. In this study, sensitivity analysis of the key erosion indicators on the parameters controlling hydraulic erosion is conducted. A novel calibration method for the erosion coefficient is presented based on sensitivity analysis. After validating against simulation results and laboratory test findings, the proposed calibration method is applied to a hypothetical long-term hydraulic erosion case. The results show that the maximum hydraulic erosion time is sensitive to all considered parameters (erosion coefficient, initial fraction of fluidized solid particle, initial porosity and maximum porosity), while the erosion curve shape is only sensitive to the initial porosity and the maximum porosity. The validation by existing simulation results shows that the proposed calibration method is robust and internally consistent. The validation by experimental results indicates that the proposed calibration method also has high external validity. Finally, the proposed calibration method is applied to hypothetical long-term erosion in a grouted area. The results show that the hydraulic erosion effect in the grouted area becomes increasingly severe over time. This study contributes toward a more efficient calibration of the erosion coefficient, especially for scenarios in the absence of testing porosity evolution data. The research outcome provides a theoretical foundation for the safety assessment and sustainability analysis of geotechnical structures that are subject to hydraulic erosion.
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| 5. |
- Huang, Xiaoli, et al.
(författare)
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High-temperature superconductivity in sulfur hydride evidenced by alternating-current magnetic susceptibility
- 2019
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Ingår i: National Science Review. - : Oxford University Press. - 2095-5138 .- 2053-714X. ; 6:4, s. 713-718
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Tidskriftsartikel (refereegranskat)abstract
- The search for high-temperature superconductivity is one of the research frontiers in physics. In the sulfur hydride system, an extremely high Tc (∼200 K) has been recently developed at pressure. However, the Meissner effect measurement above megabar pressures is still a great challenge. Here, we report the superconductivity identification of sulfur hydride at pressure, employing an in situ alternating-current magnetic susceptibility technique. We determine the superconducting phase diagram, finding that superconductivity suddenly appears at 117 GPa and Tc reaches 183 K at 149 GPa before decreasing monotonically with increasing pressure. By means of theoretical calculations, we elucidate the variation of Tc in the low-pressure region in terms of the changing stoichiometry of sulfur hydride and the further decrease in Tc owing to a drop in the electron–phonon interaction parameter λ. This work provides a new insight into clarifying superconducting phenomena and anchoring the superconducting phase diagram in the hydrides.
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| 6. |
- Ma, Dan, et al.
(författare)
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A global optimization-based method for the prediction of water inrush hazard from mining floor
- 2018
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 10:11
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Tidskriftsartikel (refereegranskat)abstract
- Water inrush hazards can be effectively reduced by a reasonable and accurate soft-measuring method on the water inrush quantity from the mine floor. This is quite important for safe mining. However, there is a highly nonlinear relationship between the water outburst from coal seam floors and geological structure, hydrogeology, aquifer, water pressure, water-resisting strata, mining damage, fault and other factors. Therefore, it is difficult to establish a suitable model by traditional methods to forecast the water inrush quantity from the mine floor. Modeling methods developed in other fields can provide adequate models for rock behavior on water inrush. In this study, a new forecast system, which is based on a hybrid genetic algorithm (GA) with the support vector machine (SVM) algorithm, a model structure and the related parameters are proposed simultaneously on water inrush prediction. With the advantages of powerful global optimization functions, implicit parallelism and high stability of the GA, the penalty coefficient, insensitivity coefficient and kernel function parameter of the SVM model are determined as approximately optimal automatically in the spatial dimension. All of these characteristics greatly improve the accuracy and usable range of the SVM model. Testing results show that GA has a useful ability in finding optimal parameters of a SVM model. The performance of the GA optimized SVM (GA-SVM) is superior to the SVM model. The GA-SVM enables the prediction of water inrush and provides a promising solution to the predictive problem for relevant industries.
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| 7. |
- Ma, Dan, et al.
(författare)
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A state-of-the-art review on rock seepage mechanism of water inrush disaster in coal mines
- 2022
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Ingår i: International Journal of Coal Science & Technology. - : Springer Nature. - 2095-8293 .- 2198-7823. ; 9:1
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Forskningsöversikt (refereegranskat)abstract
- Water inrush is one of the most dangerous disasters in coal mining. Due to the large-scale mining and complicated hydrogeological conditions, thousands of deaths and huge economic losses have been caused by water inrush disasters in China. There are two main factors determining the occurrence of water inrush: water source and water-conducting pathway. Research on the formation mechanism of the water-conducting pathway is the main direction to prevent and control the water inrush, and the seepage mechanism of rock mass during the formation of the water-conducting pathway is the key for the research on the water inrush mechanism. This paper provides a state-of-the-art review of seepage mechanisms during water inrush from three aspects, i.e., mechanisms of stress-seepage coupling, flow regime transformation and rock erosion. Through numerical methods and experimental analysis, the evolution law of stress and seepage fields in the process of water inrush is fully studied; the fluid movement characteristics under different flow regimes are clearly summarized; the law of particle initiation and migration in the process of water inrush is explored, and the effect of rock erosion on hydraulic and mechanical properties of the rock media is also studied. Finally, some limitations of current research are analyzed, and the suggestions for future research on water inrush are proposed in this review.
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| 8. |
- Ma, Dan, et al.
(författare)
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Creep-erosion coupling water inrush model of weakly cemented fault rock mass
- 2023
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Ingår i: Meitan Xuebao/Journal of the China Coal Society. - : China Coal Society. - 0253-9993. ; 48:6, s. 2453-2464
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Tidskriftsartikel (refereegranskat)abstract
- In order to investigate the temporal-spatial evolution properties of the water inrush disaster process of weakly cemented fault rock mass, a creep-erosion coupling water inrush model of weakly cemented fault rock mass is established. This model expands the equivalent continuum seepage theory, and a creep submodel and an erosion submodel are established respectively. The proposed creep submodel fully considers the mass conversion among materials, stress-strain and strain-porosity relationships. The proposed erosion submodel fully considers the mass conservation, particle migration and non-Darcy flow laws. According to the superposition principle of the mass conservation equations and three influence relationships (i.e., porosity-effective stress, porosity-creep material coefficient and creep strain-porosity-permeability relationships), the coupling between the submodels is realized, and the governing equations of the one-dimensional radial seepage direction coupling model are given. The solution conditions of the water inrush model are set, and the numerical computation method of the model in the temporal-spatial domain is established based on the COMSOL Multiphysics. By comparing the laboratory experimental results and the model calculation results of porosity evolution, the validity of the creep-erosion coupling model of weakly cemented surrounding rock is verified. On this basis, the temporal-spatial evolution law of the creep-erosion characteristics of weakly cemented surrounding rocks of the roadway is solved and analyzed. The calculated results show that in terms of the creep characteristics evolution, the effective stress decreases and the creep strain increases with time, and the samples exhibit the accelerated creep characteristics. The inhomogeneity of the spatial distribution of effective stress and creep strain increases with the creep-erosion coupling process. As for the evolution of the erosion characteristics, in the initial stage of the creep-erosion coupling process, the fine rock particles migrate out continuously under the effect of water flow, the volume fraction of fluidized particles, the permeability and flow velocity continuously increase, and new water-conducting channels are constantly formed in the weakly cemented rock mass. Subsequently, the erosion effect is weakened and finally stagnates due to the increasing creep effect. The closer to the inner wall of the roadway, the stronger the erosion effect. The spatial distribution of porosity and permeability after the stagnation of erosion shows obvious inhomogeneous characteristics, and the spatial distribution of water pressure presents a nonlinear-linear-nonlinear trend in the creep-erosion coupling process.
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| 9. |
- Ma, D., et al.
(författare)
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Numerical Simulation of Water–Silt Inrush Hazard of Fault Rock : A Three-Phase Flow Model
- 2022
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Ingår i: Rock Mechanics and Rock Engineering. - : Springer Nature. - 0723-2632 .- 1434-453X. ; 55:8, s. 5163-5182
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Tidskriftsartikel (refereegranskat)abstract
- Fault rock is a typical hazardous material of water–silt inrush during the excavation in underground mines. To investigate hydraulic characteristics of fault rock during the water–silt inrush, a one-dimensional radial three-phase flow model of water–rock–silt was established in this study. In the proposed model, the mass conservation and continuity equations of the three-phase flow were obtained; the rock particle migration and the momentum conservation of the three-phase fluid migration were described by erosion constitutive equations and non-Darcy flow equations, respectively. The laboratory tests of porosity and the evolution of volume discharge rate were compared, and the accuracy of the proposed three-phase model was verified by the comparison results. From the test and numerical results, a high standard deviation of repeated results is observed in the case with high silt concentrations, and the erosion effect is inhibited by the silt flow. Last but not least, the temporal–spatial distribution of hydraulic properties is obtained by the numerical simulation: With the progress of the three-phase flow, rock particles near the fluid outlet are first fluidized and constantly migrate outward, resulting in an increase of the porosity and permeability in fault rock. Subsequently, water-conducting pathways are gradually formed inside the fault rock, and then more fluidized rock particles flow out. Finally, the fluidized rock particles have completely migrated, and the porosity and permeability tend to be stable with the more significant non-uniform spatial distribution.
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| 10. |
- Ma, Dan, et al.
(författare)
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Water–rock two-phase flow model for water inrush and instability of fault rocks during mine tunnelling
- 2023
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Ingår i: International Journal of Coal Science and Technology. - : Springer Nature. - 2095-8293 .- 2198-7823. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Water inrush hazard is one of the major threats in mining tunnel construction. Rock particle migration in the seepage process is the main cause of water inrush pathway and rock instability. In this paper, a radial water–rock mixture flow model is established to study the evolution laws of water inrush and rock instability. The reliability of the proposed model is verified by the experimental data from a previous study. Through the mixture flow model, temporal-spatial evolution laws of different hydraulic and mechanical properties are analysed. And the proposed model’s applicability and limitations are discussed by comparing it with the existing water inrush model. The result shows that this model has high accuracy both in temporal evolution and spatial distribution. The accuracy of the model is related to the fluctuation caused by particle migration and the deviation of the set value. During the seepage, the porosity, permeability, volume discharge rate and volume concentration of the fluidized particle increase rapidly due to the particle migration, and this phenomenon is significant near the fluid outlet. As the seepage progresses, the volume concentration at the outlet decreases rapidly after reaching the peak, which leads to a decrease in the growth rate of permeability and porosity, and finally a stable seepage state can be maintained. In addition, the pore pressure is not fixed during radial particle migration and decreases with particle migration. Under the effect of particle migration, the downward radial displacement and decrease in effective radial stress are observed. In addition, both cohesion and shear stress of the rock material decreased, and the rock instability eventually occurred at the outlet.
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