Aqueous zinc metal batteries(AZMBs)face significant challenges in achieving reversibility and cycling stability,primarily due to hydrogen evolution reactions(HER)and zinc dendrite growth.In this study,by employing car...Aqueous zinc metal batteries(AZMBs)face significant challenges in achieving reversibility and cycling stability,primarily due to hydrogen evolution reactions(HER)and zinc dendrite growth.In this study,by employing carefully designed cells that approximate the structural characteristics of practical batteries,we revisit this widely held view through in-operando X-ray radiography to examine zinc dendrite formation and HER under nearpractical operating conditions.While conventional understanding emphasizes the severity of these processes,our findings suggest that zinc dendrites and HER are noticeably less pronounced in dense,real-operation configurations compared to modified cells,possibly due to a more uniform electric field and the suppression of triple-phase boundaries.This study indicates that other components,such as degradation at the cathode current collector interface and configuration mismatches within the full cell,may also represent important barriers to the practical application of AZMBs,particularly during the early stages of electrodeposition.展开更多
Unsecured legacy wells pose significant risks to carbon capture and storage(CCS)as they present potential leakage pathways for stored CO_(2) to return to the atmosphere.In the UK,legacy wells must be assessed for a ca...Unsecured legacy wells pose significant risks to carbon capture and storage(CCS)as they present potential leakage pathways for stored CO_(2) to return to the atmosphere.In the UK,legacy wells must be assessed for a carbon storage permit to be granted and high-risk wells require costly remediation.We use a well risk assessment scheme to evaluate the risk of wells in the Southern North Sea.We then combine our well risk assessment with investigation using the analytical tool CO2BLOCK,which relies on a gravity current model to estimate pressure and plume migration distances.We evaluate the Viking,Camelot and Poseidon projects,which plan to inject CO_(2) into the depleted reservoirs of Southern North Sea gas fields.Carbon dioxide plumes are typically several kilometers wide,and it should be possible to avoid plume migration to high-risk legacy wells.In contrast,pressure fields produced by CO_(2) injection are tens of kilometers wide and low magnitude pressure increases frequently extend beyond the bounds of storage licence areas.The pressure fields encounter hundreds of wells and in the cases of the Camelot and Poseidon projects,interact with each other.展开更多
The Neoproterozoic Jiangnan orogen plays an important role in the study of the Precambrian tectonic evolution of South China. The tectonic nature of the Neoproterozoic sedimentary basins is still controversial, due to...The Neoproterozoic Jiangnan orogen plays an important role in the study of the Precambrian tectonic evolution of South China. The tectonic nature of the Neoproterozoic sedimentary basins is still controversial, due to poor understanding of the sedimentary sequences and the lack of geochronological data. Here, we present sedimentological, provenance and geochronological data from the Heshangzhen Group in the eastern Jiangnan orogen. Sedimentological analysis shows that the Luojiamen Formation was deposited in a submarine fan, and the overlying Hongchicun Formation was deposited in front of a fan delta. The youngest detrital zircons constrain the lower Luojiamen and Hongchicun formations with ages of 827.3 ± 8.4 Ma and 825 ± 12 Ma, respectively. The sandstones of the Luojiamen Formation are characterized by a large number of intermediate to felsic volcanic grains, suggesting a volcanic arc source. In contrast, quartz and sedimentary lithic grains increase in the Hongchicun Formation, showing a new input from a collisional orogenic source. Detrital zircon from six sandstone samples in the Luojiamen and Hongchicun formations yield similar age spectra of 930–820 Ma with a peak at ca. 845–860 Ma, with one main cluster at 930–820 Ma. Detrital zircons of 930–845 Ma show a positive value of εHf(t)(+2.4 to +11, mean +7.6), which is similar to the volcanic arc of the nearby Shuangxiwu Group. There are a minor group of zircons with U-Pb ages ranging from 820 Ma to 845 Ma from the middle part of the Luojiamen Formation and Hongchicun Formation, with εHf(t) values between-20 to +2.4, which are consistent with the characteristics of the Shuangqiaoshan Group. within light of the bidirectional paleocurrents in the Luojiamen Formation, it is speculated that the zircons of 820–845 Ma were recycled from the Shuangqiaoshan Group, which is derived from a continental arc to the northwest. Our data suggests that the Luojiamen Formation was formed in an inter-arc basin, while the Hongchicun Formation was formed in an accretionary wedge-top basin. When juxtaposed with the conglomeratic characteristics at the bottom of the Luojiamen Formation, it is believed that the unconformity represented by the ‘Shen Gong Movement' reflects the rapid erosion and accumulation process of island arc volcanic material. The disconformity between the Luojiamen and Hongchicun formations is the imprint of transition from inter-arc basin to accretionary wedge-top basin,which represents the collision between the Shuangxiwu arc and the Yangtze Plate.展开更多
The opening, subduction and final closure of the Paleo-Asian Ocean led to the formation of the Central Asian Orogenic Belt. Controversy has long surrounded the timing of final closure of the Paleo-Asian Ocean. Here we...The opening, subduction and final closure of the Paleo-Asian Ocean led to the formation of the Central Asian Orogenic Belt. Controversy has long surrounded the timing of final closure of the Paleo-Asian Ocean. Here we present zircon U-Pb ages and petrological, geochemical and in situ Hf isotope data for the Xierzi biotite monzogranite pluton, Linxi, SE Inner Mongolia. U-Pb dating of zircon by LA-ICP-MS yields a middle Permian emplacement age(268.7 ± 2.3 Ma) for the Xierzi pluton that is dominated by biotite monzogranites with high SiO_2(71.2-72.8 wt.%),alkali(Na_2 O + K_2 O =8.05-8.44 wt.%), Al_2 O_3(14.4-15.2 wt.%) and Fe_2 O_3~T relative to low MgO contents, yielding Fe_2 O_3~T/MgO ratios of 2.87-3.44, and plotting within the high-K calc-alkaline field on a SiO_2 vs. K_2 O diagram. The aluminum saturation indexes(A/CNK) of the biotite monzogranites range from 1.06 to 1.19, corresponding to weakly to strongly peraluminous. They are enriched in rare earth elements(REE), high field strength elements(HFSEs; Zr,Hf). and large ion lithophile elements(LILEs; Rb, U, Th). The LREEs are enriched relative to the HREEs,with a distinct negative Eu anomaly in a chondrite-normalized REE diagram. Geochemically, the Xierzi biotite monzogranite is classified as an aluminous A-type granite, with all samples plotting within the A2-type granite field on a Y/Nb vs. Rb/Nb diagram. Zircon ε_(Hf)(t) values and two-stage modal ages of the zircons within the pluton range from +4.80 to +13.65 and from 983 to 418 Ma, respectively, indicating that the primary magma was generated through partial melting of felsic rocks from juvenile crust.Consequently, these results demonstrate that the Xierzi pluton formed under the post-orogenic extensional setting after arc-continent collision in the middle Permian.展开更多
In order to optimise the safety of underground rock engineering construction and the long-term security of the resultant facilities, it is necessary to have a knowledge of the likely hazards. These risks or hazards fa...In order to optimise the safety of underground rock engineering construction and the long-term security of the resultant facilities, it is necessary to have a knowledge of the likely hazards. These risks or hazards fall into the four categories of 'known beforehand and relatively easily addressed', 'known beforehand and not easily addressed', 'not known beforehand and relatively easily addressed', and 'not known beforehand and not easily addressed'. This paper describes how these four types of hazard can be incorporated into a design methodology approach, including the process by which the relevant mechanical rock mass parameters can be recognised for modelling and hence predictive purposes. In particular, there is emphasis on the fact that information and judgement are the keys to safety——whether the hazards are known or unknown before construction proceeds.展开更多
In response to new European Union regulations,studies are underway to mitigate accumulation of toxic cadmium(Cd)in cacao(Theobroma cacao,Tc).This study advances such research with Cd isotope analyses of 19 genetically...In response to new European Union regulations,studies are underway to mitigate accumulation of toxic cadmium(Cd)in cacao(Theobroma cacao,Tc).This study advances such research with Cd isotope analyses of 19 genetically diverse cacao clones and yeast transformed to express cacao natural resistance-associated macrophage protein(NRAMP5)and heavy metal ATPases(HMAs).The plants were enriched in light Cd isotopes relative to the hydroponic solution withΔ^(114/110)Cd_(tot-sol)=−0.22±0.08‰.Leaves show a systematic enrichment of isotopically heavy Cd relative to total plants,in accord with closed-system isotope fractionation ofΔ^(114/110)C_(dseq-mob)=−0.13‰,by sequestering isotopically light Cd in roots/stems and mobilisation of remaining Cd to leaves.The findings demonstrate that(i)transfer of Cd between roots and leaves is primarily unidirectional;(ii)different clones utilise similar pathways for Cd sequestration,which differ from those of other studied plants;(iii)clones differ in their efficiency of Cd sequestration.Transgenic yeast that expresses TcNRAMP5(T.cacao natural resistance-associated macrophage gene)had isotopically lighter Cd than did cacao.This suggests that NRAMP5 transporters constitute an important pathway for uptake of Cd by cacao.Cd isotope signatures of transgenic yeast expressing HMA-family proteins suggest that they may contribute to Cd sequestration.The data are the first to record isotope fractionation induced by transporter proteins in vivo.展开更多
Deep coal seams are one of the world’s most widespread deposits for carbon dioxide(C02)disposal and are generally located near large point sources of CO_(2)emissions.The injection of CO_(2)into coal seams has great p...Deep coal seams are one of the world’s most widespread deposits for carbon dioxide(C02)disposal and are generally located near large point sources of CO_(2)emissions.The injection of CO_(2)into coal seams has great potential to sequester CO_(2)while simultaneously enhancing coalbed methane(CO_(2)-ECBM)recovery.Pilot tests of CO_(2)-ECBM have been conducted in coal seams worldwide with favorable early results.However,one of the main technical barriers in coal seams needs to be resolved:Injecting CO_(2)reduces coal permeability and well injectivity.Here,using in situ synchrotron X-ray microtomography,we provide the first observational evidence that injecting nitrogen(N_(2))can reverse much of this lost permeability by reopening fractures that have closed due to coal swelling induced by CO_(2)adsorption.Our findings support the notion that injecting minimally treated flue gas-a mixture of mainly N_(2) and CO_(2)-is an attractive alternative for ECBM recovery instead of pure CO_(2)injection in deep coal seams.Firstly,flue gas produced by power plants could be directly injected after particulate removal,thus avoiding high CO_(2)-separation costs.Secondly,the presence of N_(2)makes it possible to maintain a sufficiently high level of coal permeability.These results suggest that flue-gas ECBM for deep coal seams may provide a promising path toward net-zero emissions from coal mines.展开更多
In this paper,the HRTEM lattice fringe micrograph of Caocun No.2 coal was extracted by ArcGIS,the length and orientation of the fringes were calculated,and the rose diagram for the lattice fringe micrograph was drawn ...In this paper,the HRTEM lattice fringe micrograph of Caocun No.2 coal was extracted by ArcGIS,the length and orientation of the fringes were calculated,and the rose diagram for the lattice fringe micrograph was drawn by Matlab.By controlling the segmentation points of each lattice fringe,the coordinates of the segmentation points were processed by a self-programmed Python program,and then a series of curvature characterizations including segmentation angle,cumulative angle and tortuosity were performed for lattice fringes with different lengths.The results show that Caocun No.2 coal is mainly composed of short naphthalene fringes.Lattice fringes with the length ranging from 0.3 nm to 1.14 nm account for more than 90%of the total number of fringes,and the number of polynuclear aromatic rings was 2-4.The direction of lattice fringes is concentrated between 110°and 120°,which indicates well structural orientation of lattice fringes.The number of segment angles ranging from 0°to 20°account for about half of the total,which reflects the structural orientation further.For fringes with the length ranging from 0.3 nm to 1.14 nm,the cumulative angles are mainly concentrated at 4°to 160°.Fringes with the tortuosity in the range of 1.0-1.1 are more than 92%of the total number of fringes.In addition,short fringes have large curvature,which shows significant effects on the placement and frequency of non-six-membered rings and lattice imperfection in the aromatic structure.展开更多
The Xiaobaishitou gabbro-diorite pluton comprises a medium-grained gabbro-diorite suite and a fine-grained diorite suite,which intrude the Kawabulag Group in the East Tianshan Orogen of the Central Asian Orogenic Belt...The Xiaobaishitou gabbro-diorite pluton comprises a medium-grained gabbro-diorite suite and a fine-grained diorite suite,which intrude the Kawabulag Group in the East Tianshan Orogen of the Central Asian Orogenic Belt(CAOB).A combination of mineral chemistry,zircon U-Pb age,whole-rock geochemistry,Sr-Nd isotopes,and in situ zircon Hf isotopes for newly found gabbro-diorite from the Xiaobaishitou district in the Central Tianshan Terrane(CTT)is presented to investigate the petrogenesis and tectonic or even crustal evolution of the East Tianshan Orogen.Laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)zircon U-Pb analyses indicate that the gabbro-diorite was formed at 324.7±2.4 Ma.The isolated clinopyroxene formed under higher P-T-fO_(2)melt conditions(10.7–14.6 kbar;1199–1269℃;high fO_(2))than those for the hornblende,plagioclase,and zircon(557–687℃;moderate fO_(2))in the gabbro-diorite,which reveals a multilevel,magmatic storage system.The gabbro-diorite is characterized by fractioned REE patterns,enriched LILEs(e.g.,Ba and Pb),negative anomalies of HFSEs(e.g.,Nb and Ta),and low La/Yb and Sr/Y ratios,which are typically indicative of crustal contamination and accounted for by subduction-related fluids.The rock also characterized by typical features of high compatible elements(MgO=3.14–11.65 wt%,Cr=1–157 ppm,Ni=6–830 ppm),high Mg^(#)(47–74),positiveε_(Hf)(t)values(+5.1 to+10.3)andε_(Nd)(t)values(+2.3 to+4.4).These features suggest that the Xiaobaishitou gabbro-diorite was most likely derived from metasomatic mantle and contaminated minor crustal components.Taking into account the spatial and temporal distribution of the Carboniferous magmatic rocks in the CTT,we suggest the formation of the Xiaobaishitou gabbro-diorite was attributed to southward subduction of the Kangguer Ocean.展开更多
Effective elastic properties of porous media are known to be significantly influenced by porosity.In this paper,we investigated the influence of another critical factor,the inter-grain cementation stiffness,on the eff...Effective elastic properties of porous media are known to be significantly influenced by porosity.In this paper,we investigated the influence of another critical factor,the inter-grain cementation stiffness,on the effective elastic properties of a granular porous rock(Bentheim sandstone)using an advanced numerical workflow with realistic rock microstructure and a theoretical model.First,the disparity between the experimentally tested elastic properties of Bentheim sandstone and the effective elastic properties predicted by empirical equations was analysed.Then,a micro-computed tomography(CT)-scan based approach was implemented with digital imaging software AVIZO to construct the 3D(three-dimensional)realistic microstructure of Bentheim sandstone.The microstructural model was imported to a mechanics solver based on the 3D finite element model with inter-grain boundaries modelled by cohesive elements.Loading simulations were run to test the effective elastic properties for different shear and normal intergrain cementation stiffness.Finally,a relation between the macroscale Young’s modulus and inter-grain cementation stiffness was derived with a theoretical model which can also account for porosity explicitly.Both the numerical and theoretical results indicate the influence of the inter-grain cementation stiffness,on the effective elastic properties is significant for porous sandstone.The calibrated normal and shear stiffnesses at the inter-grain boundaries are 1.2×10^(5) and 4×10^(4) GPa/m,respectively.展开更多
Failure of irregular rock samples may provide implications in the rapid estimation of rock strength,which is imperative in rock engineering practice.In this work,analytical,experimental and numerical investigations we...Failure of irregular rock samples may provide implications in the rapid estimation of rock strength,which is imperative in rock engineering practice.In this work,analytical,experimental and numerical investigations were carried out to study the mechanical properties and failure characteristics of rock spheres under paired point loads.Analytical solutions indicted that with the increase in sample size(contact angle)and decrease in Poisson’s ratio,the uneven tensile stress in theta direction decreased.Then laboratory experiments were carried out to investigate the load characteristics and failure mode of spherical marble samples with different sizes subjected to a pair of diametral point loads.The discrete element method(DEM)was adopted to study the failure process of rock spheres.The effect of the sphere diameter on the point load contact angle was examined in terms of peak load,crushed zone distribution and energy dissipation.Experimental and numerical results showed that the samples primarily fail in tension,with crushed zones formed at both loading points.With increase in the sample size,the contact angle,crushed area and total work increase.As the specimen diameter increases from 30 mm to 50 mm,the peak load on the specimen increases from 3.6 kN to 8.8 kN,and the percentage of crushed zone(ratio of crushing zone to sample radius,d/r)increased from 0.191 to 0.262.The results of the study have implications for understanding the failure of irregular rock specimens under point loading conditions and their size effects.展开更多
The stable isotope systems of the transition metals potentially provide constraints on the current and past operation of the biological pump,and on the state of ocean redox in Earth history.Here we focus on two exempl...The stable isotope systems of the transition metals potentially provide constraints on the current and past operation of the biological pump,and on the state of ocean redox in Earth history.Here we focus on two exemplar metals,nickel(Ni)and zinc(Zn).The oceanic dissolved pool of both elements is isotopically heavier than the known inputs,implying an output with light isotope compositions.The modern oceanic cycle of both these elements is dominated by biological uptake into photosynthesised organic matter and output to sediment.It is increasingly clear,however,that such uptake is associated with only very minor isotope fractionation.We suggest that the isotopic balance is instead closed by the sequestration of light isotopes to sulphide in anoxic and organic-rich sediments,so that it is ocean chemistry that controls these isotope systems,and suggesting a different but equally interesting array of questions in Earth history that can be addressed with these systems.展开更多
Mixed ionic electronic conductors(MIECs)have attracted increasing attention as anode materials for solid oxide fuel cells(SOFCs)and they hold great promise for lowering the operation temperature of SOFCs.However,there...Mixed ionic electronic conductors(MIECs)have attracted increasing attention as anode materials for solid oxide fuel cells(SOFCs)and they hold great promise for lowering the operation temperature of SOFCs.However,there has been a lack of understanding of the performance-limiting factors and guidelines for rational design of composite metal-MIEC electrodes.Using a newly-developed approach based on 3 D-tomography and electrochemical impedance spectroscopy,here for the first time we quantify the contribution of the dual-phase boundary(DPB)relative to the three-phase boundary(TPB)reaction pathway on real MIEC electrodes.A new design strategy is developed for Ni/gadolinium doped ceria(CGO)electrodes(a typical MIEC electrode)based on the quantitative analyses and a novel Ni/CGO fiber-matrix structure is proposed and fabricated by combining electrospinning and tape-casting methods using commercial powders.With only 11.5 vol%nickel,the designer Ni/CGO fiber-matrix electrode shows 32%and 67%lower polarization resistance than a nano-Ni impregnated CGO scaffold electrode and conventional cermet electrode respectively.The results in this paper demonstrate quantitatively using real electrode structures that enhancing DPB and hydrogen kinetics are more efficient strategies to enhance electrode performance than simply increasing TPB.展开更多
Geological CO_(2) storage is a promising strategy for reducing greenhouse gas emissions;however,its underlying multiphase reactive flow mechanisms remain poorly understood.We conducted steady-state imbibition relative...Geological CO_(2) storage is a promising strategy for reducing greenhouse gas emissions;however,its underlying multiphase reactive flow mechanisms remain poorly understood.We conducted steady-state imbibition relative permeability experiments on sandstone from a proposed storage site,comple-mented by in situ X-ray imaging and ex situ analyses using scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDS).Despite our use of a brine that was pre-equilibrated with CO_(2),there was a significant reduction in both CO_(2) relative permeability and absolute permeability during multiphase flow due to chemical reactions.This reduction was driven by decreased pore and throat sizes,diminished connectivity,and increased irregularity of pore and throat shapes,as revealed by in situ pore-scale imaging.Mineral dissolution,primarily of feldspar,albite,and calcite,along with precipitation resulting from feldspar-to-kaolinite transformation and fines migration,were identified as contributing factors through SEM-EDS analysis.This work provides a benchmark for storage in mineralogically complex sandstones,for which the impact of chemical reactions on multiphase flow properties has been measured.展开更多
We measured Electron Spin Resonance(ESR) signal intensity and Crystallinity Index(CI) of fine-(<16 m) and coarse-grained(>16 m) quartz in surface samples collected from the Taklimakan desert in western China, th...We measured Electron Spin Resonance(ESR) signal intensity and Crystallinity Index(CI) of fine-(<16 m) and coarse-grained(>16 m) quartz in surface samples collected from the Taklimakan desert in western China, the Badain Juran, Tengger and Mu Us deserts in northern China, and the Gobi desert in southern Mongolia. The aim was to test if these two parameters can be used as the accurate provenance tracers of Asian dust. Coarse-grained quartz displays spatial variability of the ESR signal intensity within each desert and of the CI within the Taklimakan and the Mongolian Gobi deserts. Coarse-grained quartz derived from the Mongolian Gobi and northern China deserts can be differentiated from the Taklimakan desert using the ESR signal intensity. By contrast, variability of ESR signal intensity and CI of fine-grained quartz particles is distinct within the Taklimakan and the Mongolian Gobi deserts, but less significant in three deserts of northern China. Spatially, fine-grained dust originating from three major Asian dust sources(i.e., the Gobi-sandy deserts in western China, northern China and southern Mongolia) can be differentiated using the combination of the ESR and CI signals. Our results suggest that combination of the ESR and CI results can discriminate the sources of fine-grained dust better than coarse-grained dust, providing an effective approach to trace the provenance of fine-grained dust depositions on the land and in the ocean.展开更多
To understand the applicability of high-temperature preformed particle gel(HT-PPG)for control of short-circuiting in enhanced geothermal systems(EGSs),core flooding experiments were conducted on fractured granite core...To understand the applicability of high-temperature preformed particle gel(HT-PPG)for control of short-circuiting in enhanced geothermal systems(EGSs),core flooding experiments were conducted on fractured granite cores under varying fracture widths,gel particle sizes and swelling ratios.Key parameters such as injection pressure,water breakthrough pressure,and residual resistance factor were measured to evaluate HT-PPG performance.The gel exhibited strong injectability,entering granite fractures at pressure gradients as low as 0.656 MPa/m;HT-PPG yields a superior sealing performance by significantly reducing the permeability;and dehydration occurs during HT-PPG propagation,with a dehydration ratio ranging from 4.71%to 11.36%.This study reveals that HT-PPG can be injected into geothermal formations with minimal pressure yet provides strong resistance to breakthrough once in place.This balance of injectability and sealing strength makes HT-PPG effective for addressing thermal short-circuiting in EGS reservoirs.展开更多
Percussive drilling is gaining interest for both shallow and deep applications due to its potential for higher drilling rates in hard rocks.Therefore,for efficient rock breaking,the development of advanced percussive ...Percussive drilling is gaining interest for both shallow and deep applications due to its potential for higher drilling rates in hard rocks.Therefore,for efficient rock breaking,the development of advanced percussive drilling simulation tools has the potential to be transformative.Such tools must accurately capture the rock’s response to enable an effective analysis of the fragmentation process.Traditional continuum numerical methods,such as the finite element method(FEM),do not simulate discrete cracks or the contact interaction between rock fragments.The finite-discrete element method(FDEM)is a three-dimensional hybrid method that combines FEM with the discrete element method(DEM)that addresses these limitations.New FDEM simulation results of impacts on Kuru Grey granite show good agreement with published experimental data.The interpretation focuses on two significant processes in percussive drilling:crack propagation and chipping generation.FDEM successfully simulates the evolution of cracks,including radial,side,and inclined cracks,as well as crushed and cracked zones.The simulation also reproduces the coalescence of adjacent craters to generate more chippings.Additionally,the stress state,velocity field and discrete fractures simulated by FDEM provide detailed insights into the different fracture patterns for Kuru Grey granite,enhancing understanding of the fundamental underlying mechanisms.展开更多
Shales are considered to be sealing units for geological carbon storage and suitable host rocks for nuclear waste repositories due to their low permeability.However,the presence of fractures within these formations ca...Shales are considered to be sealing units for geological carbon storage and suitable host rocks for nuclear waste repositories due to their low permeability.However,the presence of fractures within these formations can significantly alter their flow,transport,and deformation behavior,which is central to the safe implementation of underground storage projects.Fractures not only increase the overall permeability of the rock but also contribute to its anisotropic behavior.This study focuses on characterizing the hydro-mechanical response of a natural fracture to aqueous fluid injection within a shaly specimen of Opalinus Clay.Laboratory experiments were performed to measure the mechanical and flow properties of intact and fractured rock specimens.Subsequently,a three-dimensional(3D)numerical model of water injection into the fractured specimen was developed.This model explicitly accounts for fracture geometry with strain-dependent aperture changes based on the cubic law assumption.Experimental measurements indicate that the fractured shale exhibits permeability up to two orders of magnitude higher than that of the intact counterpart.However,the simulations reveal that fracture permeability locally spans up to eight orders of magnitude.This significant change in permeability affects fluid flow within the rock specimen.The numerical model best reproduces the experimental results for a normal stiffness of the natural fracture of 18.7 MPa/mm at effective mean stresses below 15 MPa,and of 187.2 MPa/mm at higher confinements.This outcome highlights the critical importance of defining the hydro-mechanical parameters of fractures under realistic effective stress conditions with far-reaching implications for secure underground storage.展开更多
This paper presents the application of a novel AI-based approach,Neural Physics,to produce high-fidelity simulations of train aerodynamics.Neural Physics is built upon convolutional neural networks(CNNs),where the wei...This paper presents the application of a novel AI-based approach,Neural Physics,to produce high-fidelity simulations of train aerodynamics.Neural Physics is built upon convolutional neural networks(CNNs),where the weights are explicitly determined by classical numerical discretisation schemes rather than by training.By leveraging the power of AI technology,this recent approach results in code that can run easily on GPUs and AI processors,achieving high computational speed without sacrificing accuracy.The approach uses an implicit large eddy simulation method based on a non-linear Petrov-Galerkin method to model the unresolved turbulence.Furthermore,for higher-order finite elements,the convolutional finite element method(ConvFEM)is used,which greatly simplifies the implementation of higher-order elements within the NN 4 DPEs approach.We demonstrate the capability of Neural Physics by simulating a freight Locomotive Class 66 and a partially loaded freight train operating in an open field environment with and without cross wind.This is the first time that ConvFEM has been applied to high-speed fluid flow problems in complex geometries.The results are validated against existing numerical results and experimental measurements,and show good agreement in terms of pressure and velocity distributions around the train body.展开更多
基金the fundamental Research Funds for the central Universities(x2wjD2240360)for the funding supportMeanwhile,Engineering and Physical Sciences Research Council(EPSRC,EP/V027433/3)+2 种基金UK Research and Innovation(UKRI)under the UK government’s Horizon Europe funding(101077226,EP/Y008707/1)Faraday Institution(EP/S003053/1)Degradation project(FIRG001),Royal Society(IEC\NSFC\233361),QUB Agility Fund and Wright Technology and Research Centre(W-Tech,R5240MEE)Funding from UK aid from the UK Government through the Faraday Institution and the Transforming Energy Access Programme(Grant number FIRG050-Device engineering of Zn-based hybrid micro-flow batteries and by-product H2 collection for Emerging Economies)。
文摘Aqueous zinc metal batteries(AZMBs)face significant challenges in achieving reversibility and cycling stability,primarily due to hydrogen evolution reactions(HER)and zinc dendrite growth.In this study,by employing carefully designed cells that approximate the structural characteristics of practical batteries,we revisit this widely held view through in-operando X-ray radiography to examine zinc dendrite formation and HER under nearpractical operating conditions.While conventional understanding emphasizes the severity of these processes,our findings suggest that zinc dendrites and HER are noticeably less pronounced in dense,real-operation configurations compared to modified cells,possibly due to a more uniform electric field and the suppression of triple-phase boundaries.This study indicates that other components,such as degradation at the cathode current collector interface and configuration mismatches within the full cell,may also represent important barriers to the practical application of AZMBs,particularly during the early stages of electrodeposition.
基金supported by the Natural Environment Research Council[grant number NE/S007415/1]Shell as iCASE sponsors。
文摘Unsecured legacy wells pose significant risks to carbon capture and storage(CCS)as they present potential leakage pathways for stored CO_(2) to return to the atmosphere.In the UK,legacy wells must be assessed for a carbon storage permit to be granted and high-risk wells require costly remediation.We use a well risk assessment scheme to evaluate the risk of wells in the Southern North Sea.We then combine our well risk assessment with investigation using the analytical tool CO2BLOCK,which relies on a gravity current model to estimate pressure and plume migration distances.We evaluate the Viking,Camelot and Poseidon projects,which plan to inject CO_(2) into the depleted reservoirs of Southern North Sea gas fields.Carbon dioxide plumes are typically several kilometers wide,and it should be possible to avoid plume migration to high-risk legacy wells.In contrast,pressure fields produced by CO_(2) injection are tens of kilometers wide and low magnitude pressure increases frequently extend beyond the bounds of storage licence areas.The pressure fields encounter hundreds of wells and in the cases of the Camelot and Poseidon projects,interact with each other.
基金supported by the Geological Survey Project of the Chinese Geological Survey(DD20190043,DD20160038)。
文摘The Neoproterozoic Jiangnan orogen plays an important role in the study of the Precambrian tectonic evolution of South China. The tectonic nature of the Neoproterozoic sedimentary basins is still controversial, due to poor understanding of the sedimentary sequences and the lack of geochronological data. Here, we present sedimentological, provenance and geochronological data from the Heshangzhen Group in the eastern Jiangnan orogen. Sedimentological analysis shows that the Luojiamen Formation was deposited in a submarine fan, and the overlying Hongchicun Formation was deposited in front of a fan delta. The youngest detrital zircons constrain the lower Luojiamen and Hongchicun formations with ages of 827.3 ± 8.4 Ma and 825 ± 12 Ma, respectively. The sandstones of the Luojiamen Formation are characterized by a large number of intermediate to felsic volcanic grains, suggesting a volcanic arc source. In contrast, quartz and sedimentary lithic grains increase in the Hongchicun Formation, showing a new input from a collisional orogenic source. Detrital zircon from six sandstone samples in the Luojiamen and Hongchicun formations yield similar age spectra of 930–820 Ma with a peak at ca. 845–860 Ma, with one main cluster at 930–820 Ma. Detrital zircons of 930–845 Ma show a positive value of εHf(t)(+2.4 to +11, mean +7.6), which is similar to the volcanic arc of the nearby Shuangxiwu Group. There are a minor group of zircons with U-Pb ages ranging from 820 Ma to 845 Ma from the middle part of the Luojiamen Formation and Hongchicun Formation, with εHf(t) values between-20 to +2.4, which are consistent with the characteristics of the Shuangqiaoshan Group. within light of the bidirectional paleocurrents in the Luojiamen Formation, it is speculated that the zircons of 820–845 Ma were recycled from the Shuangqiaoshan Group, which is derived from a continental arc to the northwest. Our data suggests that the Luojiamen Formation was formed in an inter-arc basin, while the Hongchicun Formation was formed in an accretionary wedge-top basin. When juxtaposed with the conglomeratic characteristics at the bottom of the Luojiamen Formation, it is believed that the unconformity represented by the ‘Shen Gong Movement' reflects the rapid erosion and accumulation process of island arc volcanic material. The disconformity between the Luojiamen and Hongchicun formations is the imprint of transition from inter-arc basin to accretionary wedge-top basin,which represents the collision between the Shuangxiwu arc and the Yangtze Plate.
基金financially supported by the 973 Program(Grant No.2013CB429802)the Natural Science Foundation of China(Grant Nos.41272223,41340024 and 41602209)
文摘The opening, subduction and final closure of the Paleo-Asian Ocean led to the formation of the Central Asian Orogenic Belt. Controversy has long surrounded the timing of final closure of the Paleo-Asian Ocean. Here we present zircon U-Pb ages and petrological, geochemical and in situ Hf isotope data for the Xierzi biotite monzogranite pluton, Linxi, SE Inner Mongolia. U-Pb dating of zircon by LA-ICP-MS yields a middle Permian emplacement age(268.7 ± 2.3 Ma) for the Xierzi pluton that is dominated by biotite monzogranites with high SiO_2(71.2-72.8 wt.%),alkali(Na_2 O + K_2 O =8.05-8.44 wt.%), Al_2 O_3(14.4-15.2 wt.%) and Fe_2 O_3~T relative to low MgO contents, yielding Fe_2 O_3~T/MgO ratios of 2.87-3.44, and plotting within the high-K calc-alkaline field on a SiO_2 vs. K_2 O diagram. The aluminum saturation indexes(A/CNK) of the biotite monzogranites range from 1.06 to 1.19, corresponding to weakly to strongly peraluminous. They are enriched in rare earth elements(REE), high field strength elements(HFSEs; Zr,Hf). and large ion lithophile elements(LILEs; Rb, U, Th). The LREEs are enriched relative to the HREEs,with a distinct negative Eu anomaly in a chondrite-normalized REE diagram. Geochemically, the Xierzi biotite monzogranite is classified as an aluminous A-type granite, with all samples plotting within the A2-type granite field on a Y/Nb vs. Rb/Nb diagram. Zircon ε_(Hf)(t) values and two-stage modal ages of the zircons within the pluton range from +4.80 to +13.65 and from 983 to 418 Ma, respectively, indicating that the primary magma was generated through partial melting of felsic rocks from juvenile crust.Consequently, these results demonstrate that the Xierzi pluton formed under the post-orogenic extensional setting after arc-continent collision in the middle Permian.
文摘In order to optimise the safety of underground rock engineering construction and the long-term security of the resultant facilities, it is necessary to have a knowledge of the likely hazards. These risks or hazards fall into the four categories of 'known beforehand and relatively easily addressed', 'known beforehand and not easily addressed', 'not known beforehand and relatively easily addressed', and 'not known beforehand and not easily addressed'. This paper describes how these four types of hazard can be incorporated into a design methodology approach, including the process by which the relevant mechanical rock mass parameters can be recognised for modelling and hence predictive purposes. In particular, there is emphasis on the fact that information and judgement are the keys to safety——whether the hazards are known or unknown before construction proceeds.
基金supported by grants from the GCRF programmes of STFC(grants ST/P003257/1,4070200262)and UKRI(grant EP/S515875/1)to M.R.as well as funding from Mars Wrigley Confectionery to J.M.D.and M.R.and Cocoa Research UK to J.M.D.V.H.d.O.was supported by CAPES(Coordination for the Improvement of Higher Education Personnel—Brazil)[project:13462-13-0].
文摘In response to new European Union regulations,studies are underway to mitigate accumulation of toxic cadmium(Cd)in cacao(Theobroma cacao,Tc).This study advances such research with Cd isotope analyses of 19 genetically diverse cacao clones and yeast transformed to express cacao natural resistance-associated macrophage protein(NRAMP5)and heavy metal ATPases(HMAs).The plants were enriched in light Cd isotopes relative to the hydroponic solution withΔ^(114/110)Cd_(tot-sol)=−0.22±0.08‰.Leaves show a systematic enrichment of isotopically heavy Cd relative to total plants,in accord with closed-system isotope fractionation ofΔ^(114/110)C_(dseq-mob)=−0.13‰,by sequestering isotopically light Cd in roots/stems and mobilisation of remaining Cd to leaves.The findings demonstrate that(i)transfer of Cd between roots and leaves is primarily unidirectional;(ii)different clones utilise similar pathways for Cd sequestration,which differ from those of other studied plants;(iii)clones differ in their efficiency of Cd sequestration.Transgenic yeast that expresses TcNRAMP5(T.cacao natural resistance-associated macrophage gene)had isotopically lighter Cd than did cacao.This suggests that NRAMP5 transporters constitute an important pathway for uptake of Cd by cacao.Cd isotope signatures of transgenic yeast expressing HMA-family proteins suggest that they may contribute to Cd sequestration.The data are the first to record isotope fractionation induced by transporter proteins in vivo.
文摘Deep coal seams are one of the world’s most widespread deposits for carbon dioxide(C02)disposal and are generally located near large point sources of CO_(2)emissions.The injection of CO_(2)into coal seams has great potential to sequester CO_(2)while simultaneously enhancing coalbed methane(CO_(2)-ECBM)recovery.Pilot tests of CO_(2)-ECBM have been conducted in coal seams worldwide with favorable early results.However,one of the main technical barriers in coal seams needs to be resolved:Injecting CO_(2)reduces coal permeability and well injectivity.Here,using in situ synchrotron X-ray microtomography,we provide the first observational evidence that injecting nitrogen(N_(2))can reverse much of this lost permeability by reopening fractures that have closed due to coal swelling induced by CO_(2)adsorption.Our findings support the notion that injecting minimally treated flue gas-a mixture of mainly N_(2) and CO_(2)-is an attractive alternative for ECBM recovery instead of pure CO_(2)injection in deep coal seams.Firstly,flue gas produced by power plants could be directly injected after particulate removal,thus avoiding high CO_(2)-separation costs.Secondly,the presence of N_(2)makes it possible to maintain a sufficiently high level of coal permeability.These results suggest that flue-gas ECBM for deep coal seams may provide a promising path toward net-zero emissions from coal mines.
基金Supported by the National Natural Science Foundation of China(41602177,41802191,41702175)
文摘In this paper,the HRTEM lattice fringe micrograph of Caocun No.2 coal was extracted by ArcGIS,the length and orientation of the fringes were calculated,and the rose diagram for the lattice fringe micrograph was drawn by Matlab.By controlling the segmentation points of each lattice fringe,the coordinates of the segmentation points were processed by a self-programmed Python program,and then a series of curvature characterizations including segmentation angle,cumulative angle and tortuosity were performed for lattice fringes with different lengths.The results show that Caocun No.2 coal is mainly composed of short naphthalene fringes.Lattice fringes with the length ranging from 0.3 nm to 1.14 nm account for more than 90%of the total number of fringes,and the number of polynuclear aromatic rings was 2-4.The direction of lattice fringes is concentrated between 110°and 120°,which indicates well structural orientation of lattice fringes.The number of segment angles ranging from 0°to 20°account for about half of the total,which reflects the structural orientation further.For fringes with the length ranging from 0.3 nm to 1.14 nm,the cumulative angles are mainly concentrated at 4°to 160°.Fringes with the tortuosity in the range of 1.0-1.1 are more than 92%of the total number of fringes.In addition,short fringes have large curvature,which shows significant effects on the placement and frequency of non-six-membered rings and lattice imperfection in the aromatic structure.
基金supported by the National Natural Science Foundation of China Program(Grant Nos.41672072,41302074)the Third Xinjiang Scientific Expedition Program(Grant No.2021xjkk1301)。
文摘The Xiaobaishitou gabbro-diorite pluton comprises a medium-grained gabbro-diorite suite and a fine-grained diorite suite,which intrude the Kawabulag Group in the East Tianshan Orogen of the Central Asian Orogenic Belt(CAOB).A combination of mineral chemistry,zircon U-Pb age,whole-rock geochemistry,Sr-Nd isotopes,and in situ zircon Hf isotopes for newly found gabbro-diorite from the Xiaobaishitou district in the Central Tianshan Terrane(CTT)is presented to investigate the petrogenesis and tectonic or even crustal evolution of the East Tianshan Orogen.Laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)zircon U-Pb analyses indicate that the gabbro-diorite was formed at 324.7±2.4 Ma.The isolated clinopyroxene formed under higher P-T-fO_(2)melt conditions(10.7–14.6 kbar;1199–1269℃;high fO_(2))than those for the hornblende,plagioclase,and zircon(557–687℃;moderate fO_(2))in the gabbro-diorite,which reveals a multilevel,magmatic storage system.The gabbro-diorite is characterized by fractioned REE patterns,enriched LILEs(e.g.,Ba and Pb),negative anomalies of HFSEs(e.g.,Nb and Ta),and low La/Yb and Sr/Y ratios,which are typically indicative of crustal contamination and accounted for by subduction-related fluids.The rock also characterized by typical features of high compatible elements(MgO=3.14–11.65 wt%,Cr=1–157 ppm,Ni=6–830 ppm),high Mg^(#)(47–74),positiveε_(Hf)(t)values(+5.1 to+10.3)andε_(Nd)(t)values(+2.3 to+4.4).These features suggest that the Xiaobaishitou gabbro-diorite was most likely derived from metasomatic mantle and contaminated minor crustal components.Taking into account the spatial and temporal distribution of the Carboniferous magmatic rocks in the CTT,we suggest the formation of the Xiaobaishitou gabbro-diorite was attributed to southward subduction of the Kangguer Ocean.
基金The authors would like to acknowledge the support of the EC project‘SURE-Novel Productivity Enhancement Concept for a Sustainable Utilization of a Geothermal Resource-RIA’(CEC 654662,H2020).
文摘Effective elastic properties of porous media are known to be significantly influenced by porosity.In this paper,we investigated the influence of another critical factor,the inter-grain cementation stiffness,on the effective elastic properties of a granular porous rock(Bentheim sandstone)using an advanced numerical workflow with realistic rock microstructure and a theoretical model.First,the disparity between the experimentally tested elastic properties of Bentheim sandstone and the effective elastic properties predicted by empirical equations was analysed.Then,a micro-computed tomography(CT)-scan based approach was implemented with digital imaging software AVIZO to construct the 3D(three-dimensional)realistic microstructure of Bentheim sandstone.The microstructural model was imported to a mechanics solver based on the 3D finite element model with inter-grain boundaries modelled by cohesive elements.Loading simulations were run to test the effective elastic properties for different shear and normal intergrain cementation stiffness.Finally,a relation between the macroscale Young’s modulus and inter-grain cementation stiffness was derived with a theoretical model which can also account for porosity explicitly.Both the numerical and theoretical results indicate the influence of the inter-grain cementation stiffness,on the effective elastic properties is significant for porous sandstone.The calibrated normal and shear stiffnesses at the inter-grain boundaries are 1.2×10^(5) and 4×10^(4) GPa/m,respectively.
文摘Failure of irregular rock samples may provide implications in the rapid estimation of rock strength,which is imperative in rock engineering practice.In this work,analytical,experimental and numerical investigations were carried out to study the mechanical properties and failure characteristics of rock spheres under paired point loads.Analytical solutions indicted that with the increase in sample size(contact angle)and decrease in Poisson’s ratio,the uneven tensile stress in theta direction decreased.Then laboratory experiments were carried out to investigate the load characteristics and failure mode of spherical marble samples with different sizes subjected to a pair of diametral point loads.The discrete element method(DEM)was adopted to study the failure process of rock spheres.The effect of the sphere diameter on the point load contact angle was examined in terms of peak load,crushed zone distribution and energy dissipation.Experimental and numerical results showed that the samples primarily fail in tension,with crushed zones formed at both loading points.With increase in the sample size,the contact angle,crushed area and total work increase.As the specimen diameter increases from 30 mm to 50 mm,the peak load on the specimen increases from 3.6 kN to 8.8 kN,and the percentage of crushed zone(ratio of crushing zone to sample radius,d/r)increased from 0.191 to 0.262.The results of the study have implications for understanding the failure of irregular rock specimens under point loading conditions and their size effects.
文摘The stable isotope systems of the transition metals potentially provide constraints on the current and past operation of the biological pump,and on the state of ocean redox in Earth history.Here we focus on two exemplar metals,nickel(Ni)and zinc(Zn).The oceanic dissolved pool of both elements is isotopically heavier than the known inputs,implying an output with light isotope compositions.The modern oceanic cycle of both these elements is dominated by biological uptake into photosynthesised organic matter and output to sediment.It is increasingly clear,however,that such uptake is associated with only very minor isotope fractionation.We suggest that the isotopic balance is instead closed by the sequestration of light isotopes to sulphide in anoxic and organic-rich sediments,so that it is ocean chemistry that controls these isotope systems,and suggesting a different but equally interesting array of questions in Earth history that can be addressed with these systems.
基金the financial support from EPSRC(EP/P024807/1,EP/M014045/1,EP/S000933/1 and EP/N009924/1)by the EPSRC energy storage for low carbon grids project(EP/K002252/1)+3 种基金the EPSRC Joint UK-India Clean Energy center(JUICE)(EP/P003605/1)the Integrated Development of Low-Carbon Energy Systems(IDLES)project(EP/R045518/1)the Innovate UK BAFTA project,the Innovate UK for Advanced Battery Lifetime Extension(ABLE)project for funding underthe China Scholarship Council。
文摘Mixed ionic electronic conductors(MIECs)have attracted increasing attention as anode materials for solid oxide fuel cells(SOFCs)and they hold great promise for lowering the operation temperature of SOFCs.However,there has been a lack of understanding of the performance-limiting factors and guidelines for rational design of composite metal-MIEC electrodes.Using a newly-developed approach based on 3 D-tomography and electrochemical impedance spectroscopy,here for the first time we quantify the contribution of the dual-phase boundary(DPB)relative to the three-phase boundary(TPB)reaction pathway on real MIEC electrodes.A new design strategy is developed for Ni/gadolinium doped ceria(CGO)electrodes(a typical MIEC electrode)based on the quantitative analyses and a novel Ni/CGO fiber-matrix structure is proposed and fabricated by combining electrospinning and tape-casting methods using commercial powders.With only 11.5 vol%nickel,the designer Ni/CGO fiber-matrix electrode shows 32%and 67%lower polarization resistance than a nano-Ni impregnated CGO scaffold electrode and conventional cermet electrode respectively.The results in this paper demonstrate quantitatively using real electrode structures that enhancing DPB and hydrogen kinetics are more efficient strategies to enhance electrode performance than simply increasing TPB.
文摘Geological CO_(2) storage is a promising strategy for reducing greenhouse gas emissions;however,its underlying multiphase reactive flow mechanisms remain poorly understood.We conducted steady-state imbibition relative permeability experiments on sandstone from a proposed storage site,comple-mented by in situ X-ray imaging and ex situ analyses using scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDS).Despite our use of a brine that was pre-equilibrated with CO_(2),there was a significant reduction in both CO_(2) relative permeability and absolute permeability during multiphase flow due to chemical reactions.This reduction was driven by decreased pore and throat sizes,diminished connectivity,and increased irregularity of pore and throat shapes,as revealed by in situ pore-scale imaging.Mineral dissolution,primarily of feldspar,albite,and calcite,along with precipitation resulting from feldspar-to-kaolinite transformation and fines migration,were identified as contributing factors through SEM-EDS analysis.This work provides a benchmark for storage in mineralogically complex sandstones,for which the impact of chemical reactions on multiphase flow properties has been measured.
文摘We measured Electron Spin Resonance(ESR) signal intensity and Crystallinity Index(CI) of fine-(<16 m) and coarse-grained(>16 m) quartz in surface samples collected from the Taklimakan desert in western China, the Badain Juran, Tengger and Mu Us deserts in northern China, and the Gobi desert in southern Mongolia. The aim was to test if these two parameters can be used as the accurate provenance tracers of Asian dust. Coarse-grained quartz displays spatial variability of the ESR signal intensity within each desert and of the CI within the Taklimakan and the Mongolian Gobi deserts. Coarse-grained quartz derived from the Mongolian Gobi and northern China deserts can be differentiated from the Taklimakan desert using the ESR signal intensity. By contrast, variability of ESR signal intensity and CI of fine-grained quartz particles is distinct within the Taklimakan and the Mongolian Gobi deserts, but less significant in three deserts of northern China. Spatially, fine-grained dust originating from three major Asian dust sources(i.e., the Gobi-sandy deserts in western China, northern China and southern Mongolia) can be differentiated using the combination of the ESR and CI signals. Our results suggest that combination of the ESR and CI results can discriminate the sources of fine-grained dust better than coarse-grained dust, providing an effective approach to trace the provenance of fine-grained dust depositions on the land and in the ocean.
基金Supported by the U.S.Department of Energy’s Office of Energy Efficiency and Renewable Energy(EERE)under the Geothermal Technologies Office(GTO)“Innovative Methods to Control Hydraulic Properties of Enhanced Geothermal Systems”(DE-EE0009790).
文摘To understand the applicability of high-temperature preformed particle gel(HT-PPG)for control of short-circuiting in enhanced geothermal systems(EGSs),core flooding experiments were conducted on fractured granite cores under varying fracture widths,gel particle sizes and swelling ratios.Key parameters such as injection pressure,water breakthrough pressure,and residual resistance factor were measured to evaluate HT-PPG performance.The gel exhibited strong injectability,entering granite fractures at pressure gradients as low as 0.656 MPa/m;HT-PPG yields a superior sealing performance by significantly reducing the permeability;and dehydration occurs during HT-PPG propagation,with a dehydration ratio ranging from 4.71%to 11.36%.This study reveals that HT-PPG can be injected into geothermal formations with minimal pressure yet provides strong resistance to breakthrough once in place.This balance of injectability and sealing strength makes HT-PPG effective for addressing thermal short-circuiting in EGS reservoirs.
文摘Percussive drilling is gaining interest for both shallow and deep applications due to its potential for higher drilling rates in hard rocks.Therefore,for efficient rock breaking,the development of advanced percussive drilling simulation tools has the potential to be transformative.Such tools must accurately capture the rock’s response to enable an effective analysis of the fragmentation process.Traditional continuum numerical methods,such as the finite element method(FEM),do not simulate discrete cracks or the contact interaction between rock fragments.The finite-discrete element method(FDEM)is a three-dimensional hybrid method that combines FEM with the discrete element method(DEM)that addresses these limitations.New FDEM simulation results of impacts on Kuru Grey granite show good agreement with published experimental data.The interpretation focuses on two significant processes in percussive drilling:crack propagation and chipping generation.FDEM successfully simulates the evolution of cracks,including radial,side,and inclined cracks,as well as crushed and cracked zones.The simulation also reproduces the coalescence of adjacent craters to generate more chippings.Additionally,the stress state,velocity field and discrete fractures simulated by FDEM provide detailed insights into the different fracture patterns for Kuru Grey granite,enhancing understanding of the fundamental underlying mechanisms.
基金the funding from the European Research Council(ERC)under the European Union's Horizon 2020 Research and Innovation Program through the Starting Grant GEoREST(www.georest.eu)under Grant agreement No.801809IMEDEA is an accredited“Maria de Maeztu Excellence Unit”(Grant CEX2021-001198+2 种基金funded by MICIU/AEI/10.13039/501100011033)Iman R.Kivi also acknowledges the funding from the Engineering and Physical Sciences Research Council through the UKRI Postdoc Guarantee Award THMC4CCS(Grant No.EP/X026019/1)Hyunbin Kim and Roman Y.Makhnenko are supported by the US National Science Foundation(Grant No.CMMI-2239630).
文摘Shales are considered to be sealing units for geological carbon storage and suitable host rocks for nuclear waste repositories due to their low permeability.However,the presence of fractures within these formations can significantly alter their flow,transport,and deformation behavior,which is central to the safe implementation of underground storage projects.Fractures not only increase the overall permeability of the rock but also contribute to its anisotropic behavior.This study focuses on characterizing the hydro-mechanical response of a natural fracture to aqueous fluid injection within a shaly specimen of Opalinus Clay.Laboratory experiments were performed to measure the mechanical and flow properties of intact and fractured rock specimens.Subsequently,a three-dimensional(3D)numerical model of water injection into the fractured specimen was developed.This model explicitly accounts for fracture geometry with strain-dependent aperture changes based on the cubic law assumption.Experimental measurements indicate that the fractured shale exhibits permeability up to two orders of magnitude higher than that of the intact counterpart.However,the simulations reveal that fracture permeability locally spans up to eight orders of magnitude.This significant change in permeability affects fluid flow within the rock specimen.The numerical model best reproduces the experimental results for a normal stiffness of the natural fracture of 18.7 MPa/mm at effective mean stresses below 15 MPa,and of 187.2 MPa/mm at higher confinements.This outcome highlights the critical importance of defining the hydro-mechanical parameters of fractures under realistic effective stress conditions with far-reaching implications for secure underground storage.
基金Projects(EPSRC EP/Y005732/1,EP/Y018680/1,EP/T003189/1,EP/V040235/1,EP/Y024257/1 and EP/T000414/1)supported by UK Research and Innovation(UKRI),UKProject(APP44894/UKRI 1281)supported by UKRI councils(NERC,AHRC,ESRC,MRC and DEFRA),UK。
文摘This paper presents the application of a novel AI-based approach,Neural Physics,to produce high-fidelity simulations of train aerodynamics.Neural Physics is built upon convolutional neural networks(CNNs),where the weights are explicitly determined by classical numerical discretisation schemes rather than by training.By leveraging the power of AI technology,this recent approach results in code that can run easily on GPUs and AI processors,achieving high computational speed without sacrificing accuracy.The approach uses an implicit large eddy simulation method based on a non-linear Petrov-Galerkin method to model the unresolved turbulence.Furthermore,for higher-order finite elements,the convolutional finite element method(ConvFEM)is used,which greatly simplifies the implementation of higher-order elements within the NN 4 DPEs approach.We demonstrate the capability of Neural Physics by simulating a freight Locomotive Class 66 and a partially loaded freight train operating in an open field environment with and without cross wind.This is the first time that ConvFEM has been applied to high-speed fluid flow problems in complex geometries.The results are validated against existing numerical results and experimental measurements,and show good agreement in terms of pressure and velocity distributions around the train body.
