查看更多>>摘要：The global energy transition is a widespread phenomenon that requires international exchange of expe-riences and mutual learning.Germany's success in its first phase of energy transition can be attributed to its adoption of smart energy technology and implementation of electricity futures and spot marketiza-tion,which enabled the achievement of multiple energy spatial-temporal complementarities and overall grid balance through energy conversion and reconversion technologies.While China can draw from Germany's experience to inform its own energy transition efforts,its 11-fold higher annual electricity consumption requires a distinct approach.We recommend a clean energy system based on smart sector coupling(ENSYSCO)as a suitable pathway for achieving sustainable energy in China,given that renew-able energy is expected to guarantee 85％of China's energy production by 2060,requiring significant future electricity storage capacity.Nonetheless,renewable energy storage remains a significant chal-lenge.We propose four large-scale underground energy storage methods based on ENSYSCO to address this challenge,while considering China's national conditions.These proposals have culminated in pilot projects for large-scale underground energy storage in China,which we believe is a necessary choice for achieving carbon neutrality in China and enabling efficient and safe grid integration of renewable energy within the framework of ENSYSCO.
Alberto FernándezJosé A.SanchidriánPablo SegarraSantiago Gómez...
555-571页
查看更多>>摘要：A procedure to recognize individual discontinuities in rock mass from measurement while drilling(MWD)technology is developed,using the binary pattern of structural rock characteristics obtained from in-hole images for calibration.Data from two underground operations with different drilling technology and different rock mass characteristics are considered,which generalizes the application of the method-ology to different sites and ensures the full operational integration of MWD data analysis.Two approaches are followed for site-specific structural model building:a discontinuity index(DI)built from variations in MWD parameters,and a machine learning(ML)classifier as function of the drilling param-eters and their variability.The prediction ability of the models is quantitatively assessed as the rate of recognition of discontinuities observed in borehole logs.Differences between the parameters involved in the models for each site,and differences in their weights,highlight the site-dependence of the result-ing models.The ML approach offers better performance than the classical DI,with recognition rates in the range 89％to 96％.However,the simpler DI still yields fairly accurate results,with recognition rates 70％to 90％.These results validate the adaptive MWD-based methodology as an engineering solution to predict rock structural condition in underground mining operations.
查看更多>>摘要：Permeability is a key parameter for coalbed methane development.Although the absolute permeability of coal has been extensively studied,wettability and pore structure properties continue to challenge the microscopic description of water-gas flow in coal.For this purpose,we reconstructed the microstructures of low-rank coal using micro-computed tomography(micro-CT)images.Pore geometry and pore-throat parameters are introduced to establish a relationship with absolute permeability.A dual-porosity pore network model is developed to study water-gas displacement under different wetting and pore structure properties.Results show that absolute permeability is significantly affected by pore geometry and can be described using a binary quadratic function of porosity and fractal dimension.Water-gas relative perme-ability varies significantly and the residual gas saturation is lower;the crossover saturation first decreased and then increased with increasing porosity under hydrophobic conditions.While the water relative permeability is lower and a certain amount of gas is trapped in complex pore-throat networks;the crossover saturation is higher under hydrophilic conditions.Models with large percolating porosity and well-developed pore networks have high displacement efficiency due to low capillary resistance and avoidance of trapping.This work provides a systematic description of absolute permeability and water-gas relative permeability in coal microstructure for enhanced gas recovery.
查看更多>>摘要：Accurate knowledge of gas flow within the reservoir and related controlling factors will be important for enhancing the production of coal bed methane.At present,most studies focused on the permeability evo-lution of dry coal under gas adsorption equilibrium,gas flow and gas diffusion within wet coal under the generally non-equilibrium state are often ignored in the process of gas recovery.In this study,an improved apparent permeability model is proposed which accommodates the water and gas adsorption,stress dependence,water film thickness and gas flow regimes.In the process of modeling,the water adsorption is only affected by water content while the gas adsorption is time and water content depen-dent;based on poroelastic mechanics,the effective fracture aperture and effective pore radius are derived;and then the variation in water film thickness for different pore types under the effect of water content,stress and adsorption swelling are modeled;the flow regimes are considered based on Beskok's model.Further,after validation with experimental data,the proposed model was applied to numerical simulations to investigate the evolution of permeability-related factors under the effect of different water contents.The gas flow in wet coal under the non-equilibrium state is explicitly revealed.
查看更多>>摘要：Combined bodies of rock-like material and rock are widely encountered in geotechnical engineering,such as tunnels and mines.The existing theoretical models describing the stress-strain relationship of a com-bined body lack a binary feature.Based on effective medium theory,this paper presents the governing equation of the"elastic modulus"for combined and single bodies under triaxial compressive tests.A bin-ary effective medium model is then established.Based on the compressive experiment of concrete-granite combined bodies,the feasibility of determining the stress threshold based on crack axial strain is discussed,and the model is verified.The model is further extended to coal-rock combined bodies of more diverse types,and the variation laws of the compressive mechanical parameters are then discussed.The results show that the fitting accuracy of the model with the experimental curves of the concrete-granite combined bodies and various types of coal-rock combined bodies are over 95％.The crack axial strain method can replace the crack volumetric strain method,which clarifies the physical meanings of the model parameters.The variation laws of matrix parameters and crack parameters are discussed in depth and are expected to be more widely used in geotechnical engineering.
查看更多>>摘要：A consecutive joint shear strength model for soft rock joints is proposed in this paper,which takes into account the degradation law of the actual contact three-dimensional(3D)roughness.The essence of the degradation of the maximum possible dilation angle is the degradation of the 3D average equivalent dip angle of the actual contact joint asperities.Firstly,models for calculating the maximum possible dilation angle at the initial and residual shear stress stages are proposed by analyzing the 3D joint morphology characteristics of the corresponding shear stages.Secondly,the variation law of the maximum possible dilation angle is quantified by studying the degradation law of the joint micro convex body.Based on the variation law of the maximum possible dilation angle,the maximum possible shear strength model is proposed.Furthermore,a method to calculate the shear stiffness degradation in the plastic stage is pro-posed.According to the maximum possible shear strength of rock joints,the shear stress-shear displace-ment prediction model of rock joints is obtained.The new model reveals that there is a close relationship between joint shear strength and actual contact joint roughness,and the degradation of shear strength after the peak is due to the degradation of actual contact joint roughness.
查看更多>>摘要：Interlaid rock is an important component in the construction of neighborhood tunnels that supports and reinforces the area between two tunnels.However,the blasting load during excavation can sometimes damage the interlaid rock and threaten the stability of a tunnel's structure.This paper presents a case study of the small clearance section of the Liantang highway tunnel project in Shenzhen,China,where the minimum distance between the two tunnels involved is only 0.5 m.To reduce the damage to the interlaid rock caused by blasting loads,we proposed a four-part excavation method with a vibration-cushioning rock layer in the following tunnel of neighborhood tunnels.Numerical simulation was used to model the damage prevention mechanism of the vibration-cushioning rock layer and to better under-stand the propagation of cracks in the interlaid rock.Furthermore,based on the simulation results,com-bined microseismic controlled-blasting technology was implemented,using innovative blasting patterns combined with different charge structures and blasting equipment designed according to the varying thickness of the interlaid rock.Finally,this implementation succeeded in protecting interlaid rock during blasting operations.
查看更多>>摘要：In this study,the innovative use of ethylenediamine tetramethylene phosphonic sodium(EDTMPS)as a calcite depressant in scheelite flotation was investigated by flotation experiments,and its selective depression mechanism was revealed by contact angle measurement,FTIR analysis,Zeta potential test and XPS analysis.The flotation experiment results showed that scheelite and calcite could be efficiently separated under the following conditions:pulp pH=9.5,NaOL concentration of 1.5×10-4 mol/L,EDTMPS concentration of 3.0×10-5 mol/L,a scheelite concentrate with WO3 grade of 65.49％,recovery of 83.29％and separation efficiency of 65.29％could be obtained from the artificially mixed minerals.The analysis results of mineral surface properties demonstrated that EDTMPS was strongly adsorbed onto the calcite surface through the reaction between the phosphonate group and the calcium ions,which hindered NaOL adsorption and increased the hydrophilicity of calcite.However,EDTMPS had weak adsorption strength on the scheelite surface,which didn't affect further adsorption of NaOL,hence,the scheelite remained hydrophobic.Consequently,the selective adsorption of EDTMPS on the two minerals'surfaces increased a difference in wettability and thus enabling them to be separated by flotation.Finally,the mechanism model of this flotation separation process was established.
查看更多>>摘要：The utilization of an appropriate collector or surfactant is crucial for the beneficiation of low-rank coal.However,in previous studies,the selection of surfactants was primarily based on flotation procedures,which hinders the understanding of the interaction mechanism between surfactant groups and oxygen-containing functional groups at the surface of low-rank coal.In this study,we investigate the flotation of low-rank coal in the presence of a composite collector by using a combined theoretical and experimental approach.The maximum flotation mass recovery achieved was 82.89％using a 3:1 mixture of dodecane and castor oil acid.Fourier-transform infrared and X-ray photoelectron spectro-scopic analyses showed that castor oil acid was effectively adsorbed onto the surface of low-rank coal,enhancing the hydrophobicity of the coal.In addition,the diffusion coefficient of water molecules in the water-composite collector-coal system was greater than that in the dodecane system.Moreover,due to the presence of castor oil acid in the flotation process,the adsorption distance of dodecane and low-rank coal became shorter.Molecular dynamics simulations revealed that the diffusion and interac-tion of surfactant molecules at the interface of low-rank coal particles and water was enhanced because the adsorption of the dodecane-castor oil acid mixture is primarily controlled by hydrogen bonds and electrostatic attraction.Based on these results,a better surfactant for flotation of low-rank coal is also proposed.
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