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Analysis of the interaction between bolt-reinforced rock and surface support in tunnels based on convergence-confinement method

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Journal of Rock Mechanics and Geotechnical engineering 2024年第6期16卷 1936-1951页

作者： Zhenyu Sun Dingli Zhang Qian Fang Yanjuan Hou Nanqi Huangfu key laboratory for Urban underground engineering of ministry of education Beijing Jiaotong UniversityBeijing100044China

To investigate the interaction of the bolt-reinforced rock and the surface support,an analytical model of the convergence-confinement type is proposed,considering the sequential installation of the fully grouted rockbolts and the surface *** rock mass is assumed to be elastic-brittle-plastic material,obeying the linear Mohr-Coulomb criterion or the non-linear Hoek-Brown *** to the strain states of the tunnel wall at bolt and surface support installation and the relative magnitude between the bolt length and the plastic depth during the whole process,six cases are categorized upon solving the *** case is divided into three stages due to the different effects of the active rockbolts and the passive surface *** fictitious pressure is introduced to quantify the threedimensional(3D)effect of the tunnel face,and thus,the actual physical location along the tunnel axis of the analytical section can be *** using the bolt-rock strain compatibility and the rocksurface support displacement compatibility conditions,the solutions of longitudinal tunnel displacement and the reaction pressure of surface support along the tunnel axis are *** proposed analytical solutions are validated by a series of 3D numerical *** parametric studies are conducted to examine the effect of the typical parameters of rockbolts and surface support on the tunnel displacement and the reaction pressure of the surface support under different rock *** results show that the rockbolts are more effective in controlling the tunnel displacement than the surface support,which should be installed as soon as possible with a suitable *** tunnels excavated in weak rocks or with restricted displacement control requirements,the surface support should also be installed or closed timely with a certain *** proposed method provides a convenient alternative approach for the optimization of rockbolts and surface support

关键词： Analytical model Longitudinal tunnel displacement Fictitious pressure Active rockbolts Surface support reaction pressure Tunnel design

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Formation estimation and evolution mechanism of the pressure arch for non-circular tunnels under asymmetrical stress field

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Science China(Technological Sciences) 2024年第9期67卷 2919-2938页

作者： SUN ZhenYu ZHANG DingLi XU Tong CHEN Xu key laboratory for Urban underground engineering of ministry of education Beijing Jiaotong UniversityBeijing 100044China

The tunneling-induced stress redistribution is dependent on the tunnel shape and the in-situ stress field, and the previous arch characterization method based on the circumferential or maximum principal stresses is only suitable for the circular tunnels under the hydrostatic stress field. In this study, a unified characterization method of the pressure arch for non-circular tunnels under the arbitrary stress field is proposed. By comparing the variations of compressive stress in different directions due to excavation, the ratio of the most significant increase in compressive stress is presented to characterize the arch effect, and the corresponding numerical algorithm is given. Since the proposed method takes the stress element as the basic analytical model, it can be easily applied to various complex excavation situations. Thereafter, combined with the established folding catastrophic model, an objective and unified quantitative method of the pressure arch boundaries is given. Using the proposed method, the longitudinal evolution of the pressure arch is analyzed. According to the expansion rate of the arch boundaries, three evolution stages including the initial formation, rapid expansion and stabilization are categorized. Parametric studies are conducted to illustrate the effect of ground properties and support stiffness on the pressure arch formation. It is found that the ground strength parameters and burial depth affect the arch range at a decreasing rate, while they have little effect on the arch shape. The lateral pressure coefficient has a significant effect on both the shape and range of the pressure arch. Increasing the support stiffness helps reduce the pressure arch range with a decreasing rate, while the synchronous variation of the elastic moduli of the surrounding rock and support does not affect the arch range under a certain relative elastic modulus. Finally, field monitoring is conducted to validate the proposed method in actual support design.

关键词： pressure arch stress redistribution numerical simulation quantitative characterization longitudinal evolution parametric study

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A spatiotemporal deep learning method for excavation-induced wall deflections

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Journal of Rock Mechanics and Geotechnical engineering 2024年第8期16卷 3327-3338页

作者： Yuanqin Tao Shaoxiang Zeng Honglei Sun Yuanqiang Cai Jinzhang Zhang Xiaodong Pan College of Civil engineering Zhejiang University of TechnologyHangzhou310023China ministry of education(MOE)key laboratory of Soft Soils and Geoenvironmental engineering(SSGeo) Zhejiang UniversityHangzhou310058China key laboratory of Geotechnical and underground engineering of ministry of education and Department of Geotechnical engineering Tongji UniversityShanghai200092China

Data-driven approaches such as neural networks are increasingly used for deep excavations due to the growing amount of available monitoring data in practical ***,most neural network models only use the data from a single monitoring point and neglect the spatial relationships between multiple monitoring ***,most models lack flexibility in providing predictions for multiple days after monitoring *** study proposes a sequence-to-sequence(seq2seq)two-dimensional(2D)convolutional long short-term memory neural network(S2SCL2D)for predicting the spatiotemporal wall deflections induced by deep *** model utilizes the data from all monitoring points on the entire wall and extracts spatiotemporal features from data by combining the 2D convolutional layers and long short-term memory(LSTM)*** S2SCL2D model achieves a long-term prediction of wall deflections through a recursive seq2seq *** excavation depth,which has a significant impact on wall deflections,is also considered using a feature fusion *** excavation project in Hangzhou,China,is used to illustrate the proposed *** results demonstrate that the S2SCL2D model has superior prediction accuracy and robustness than that of the LSTM and S2SCL1D(one-dimensional)*** prediction model demonstrates a strong generalizability when applied to an adjacent *** on the long-term prediction results,practitioners can plan and allocate resources in advance to address the potential engineering issues.

关键词： Braced excavation Wall deflections Deep learning Convolutional layer Long short-term memory(LSTM) Sequence to sequence(seq2seq)

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A modified smoothed particle hydrodynamics method considering residual stress for simulating failure and its application in layered rock mass

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Journal of Mountain Science 2024年第6期21卷 2091-2112页

作者： XIA Chengzhi SHI Zhenming KOU Huanjia Department of Geotechnical engineering College of Civil EngineeringTongji UniversityShanghai 200092China key laboratory of Geotechnical and underground engineering of ministry of education Tongji UniversityShanghai 200092China

Residual strength is an indispensable factor in evaluating rock fracture,yet the current Smoothed Particle Hydrodynamics(SPH)framework rarely considers its influence when simulating *** improved cracking strategy considering residual stress in the base bond SPH method was proposed to simulate failures in layered rocks and slopes and verified by experimental results and other simulation methods(i.e.,the discrete element method).Modified Mohr–Coulomb failure criterion was applied to distinguish the mixed failure of tensile and *** fracture markψwas introduced to improve the kernel function after tensile damage,and the calculation of residual stress after the damage was derived after shear *** simulations were carried out to evaluate its performance under different stress and scale conditions and to verify its effectiveness in realistically reproducing crack initiation and propagation and coalescence,even fracture and *** results indicate that the improved cracking strategy precisely captures the fracture and failure pattern in layered rocks and rock *** residual stress of brittle tock is correctly captured by the improved SPH *** improved SPH method that considers residual strength shows an approximately 13%improvement in accuracy for the safety factor of anti-dip layered slopes compared to the method that does not consider residual strength,as validated against analytical *** infer that the improved SPH method is effective and shows promise for applications to continuous and discontinuous rock masses.

关键词： Smoothed particle hydrodynamics Cracking strategy Residual stress Layered rock Crack propagation

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A dynamic soil freezing characteristic curve model for frozen soil

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Journal of Rock Mechanics and Geotechnical engineering 2024年第8期16卷 3339-3352页

作者： Xiaokang Li Xu Li Jiankun Liu key laboratory of Urban underground engineering of ministry of education Beijing Jiaotong UniversityBeijing100044China School of Civil engineering Sun Yat-sen UniversityZhuhai519082China

The soil freezing characteristic curve(SFCC)plays a fundamental role in comprehending thermohydraulic behavior and numerical simulation of frozen *** study proposes a dynamic model to uniformly express SFCCs amidst varying total water contents throughout the freezing-thawing ***,a general model is proposed,wherein the unfrozen water content at arbitrary temperature is determined as the lesser of the current total water content and the reference value derived from saturated *** dynamic performance of this model is verified through test ***,in accordance with electric double layer(EDL)theory,the theoretical residual and minimum temperatures in SFCC are calculated to be-14.5℃to-20℃for clay particles and-260℃,*** ensure that the SFCC curve ends at minimum temperature,a correction function is introduced into the general ***,a simplified dynamic model is proposed and investigated,necessitating only three parameters inherited from the general ***,both general and simplified models are evaluated based on a test database and proven to fit the test data exactly across the entire temperature *** recommended parameter values for various types of soils are ***,this study provides not only a theoretical basis for most empirical equations but also proposes a new and more general equation to describe the SFCC.

关键词： Frozen soils Unsaturated soils Soil freezing characteristic curve(SFCC) Mathematic models

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Integrated multi-scale approach combining global homogenization and local refinement for multi-field analysis of high-temperature superconducting composite magnets

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Applied Mathematics and Mechanics(English Edition) 2024年第5期45卷 747-762页

作者： Hanxiao GUO Peifeng GAO Xingzhe WANG key laboratory of Mechanics on Western Disaster and Environment of ministry of education Key Laboratory of Special Function Materials and Structure Design of Ministry of EducationCollege of Civil Engineering and MechanicsLanzhou UniversityLanzhou 730000China

Second-generation high-temperature superconducting(HTS)conductors,specifically rare earth-barium-copper-oxide(REBCO)coated conductor(CC)tapes,are promising candidates for high-energy and high-field superconducting *** respect to epoxy-impregnated REBCO composite magnets that comprise multilayer components,the thermomechanical characteristics of each component differ considerably under extremely low temperatures and strong electromagnetic *** numerical models include homogenized orthotropic models,which simplify overall field calculation but miss detailed multi-physics aspects,and full refinement(FR)ones that are thorough but computationally ***,we propose an extended multi-scale approach for analyzing the multi-field characteristics of an epoxy-impregnated composite magnet assembled by HTS pancake *** approach combines a global homogenization(GH)scheme based on the homogenized electromagnetic T-A model,a method for solving Maxwell's equations for superconducting materials based on the current vector potential T and the magnetic field vector potential A,and a homogenized orthotropic thermoelastic model to assess the electromagnetic and thermoelastic properties at the macroscopic *** then identify“dangerous regions”at the macroscopic scale and obtain finer details using a local refinement(LR)scheme to capture the responses of each component material in the HTS composite tapes at the mesoscopic *** results of the present GH-LR multi-scale approach agree well with those of the FR scheme and the experimental data in the literature,indicating that the present approach is accurate and *** proposed GH-LR multi-scale approach can serve as a valuable tool for evaluating the risk of failure in large-scale HTS composite magnets.

关键词： epoxy-impregnated high-temperature superconducting(HTS)magnet multi-scale method global homogenization(GH) local refinement(LR) multi-field analysis

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Ultrafast micro/nano-manufacturing of metastable materials for energy

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National Science Review 2024年第4期11卷 283-298页

作者： Xiaoya Cui Yanchang Liu Yanan Chen School of Materials Science and engineering Key Laboratory of Advanced Ceramics and Machining Technology(Ministry of Education) and Tianjin Key Laboratory of Composite and Functional MaterialsTianjin University ministry of education key laboratory of Protein Sciences School of Life SciencesTsinghua University

The structural engineering of metastable nanomaterials with abundant defects has attracted much attention in energy-related fields. The high-temperature shock(HTS) technique, as a rapidly developing and advanced synthesis strategy, offers significant potential for the rational design and fabrication of high-quality nanocatalysts in an ultrafast, scalable, controllable and eco-friendly way. In this review, we provide an overview of various metastable micro-and nanomaterials synthesized via HTS, including single metallic and bimetallic nanostructures, high entropy alloys, metal compounds(e.g. metal oxides) and carbon nanomaterials. Note that HTS provides a new research dimension for nanostructures, i.e. kinetic modulation. Furthermore, we summarize the application of HTS—as supporting films for transmission electron microscopy grids—in the structural engineering of 2D materials, which is vital for the direct imaging of metastable materials. Finally, we discuss the potential future applications of high-throughput and liquid-phase HTS strategies for non-equilibrium micro/nano-manufacturing beyond energy-related *** is believed that this emerging research field will bring new opportunities to the development of nanoscience and nanotechnology in both fundamental and practical aspects.

关键词： high-temperature shock technique defect engineering metastable phase kinetic modulation non-equilibrium micro/nano-manufacturing

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Cell-free biocatalysis coupled with photo-catalysis and electro-catalysis: Efficient CO2-to-chemical conversion

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Green Energy & Environment 2024年第09期9卷 1366-1383页

作者： Junzhu Yang Chi-Kit Sou Yuan Lu key laboratory of Industrial Biocatalysis Ministry of Education Tsinghua University Department of Chemical engineering Tsinghua University

The increasing atmospheric carbon dioxide （CO2） concentration has exposed a series of crises in the earth's ecological *** to effectively fix and convert carbon dioxide into products with added value has attracted the attention of many ***-free enzyme catalytic system coupled with electrical and light have been a promising attempt in the field of biological carbon fixation in recent *** this review,the research progresses of photoenzyme catalysis,electroenzyme catalysis and photo-electroenzyme catalysis for converting carbon dioxide into chemical products in cell-free systems are systematically *** focus on reviewing and comparing various coupling methods and principles of photoenzyme catalysis and electroenzyme catalysis in cell-free systems,especially the materials used in the construction of the coupling system,and analyze and point out the characteristics and possible problems of different coupling ***,we discuss the major challenges and prospects of coupling physical signals and cell-free enzymatic catalytic systems in the field of CO2fixation,suggesting possible strategies to improve the carbon sequestration capacity of such systems.

关键词： CO 2 fixation Cell-free system Enzyme Photoenzyme catalysis Electroenzyme catalysis

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In situ embedded bismuth nanoparticles among highly porous carbon fibers for efficient carbon dioxide reduction

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Rare Metals 2024年第9期43卷 4312-4320页

作者： Wei-Jian Guo Ao Zhou Wen-Wen Cai Jin-Tao Zhang key laboratory for Colloid and Interface Chemistry (ministry of education) School of Chemistry and Chemical EngineeringShandong University

Electrocatalysis provides an optimal approach for the conversion of carbon dioxide(CO2) into high-value chemicals, thereby presenting a promising avenue toward achieve carbon neutrality. However, addressing the selectivity and stability challenges of metal catalysts in electrolytic reduction remains a daunting task. In this study, the electrospinning method is employed to fabricate porous carbon nanofibers loaded with bismuth nanoparticles with the help of in situ pyrolysis. The porous carbon nanofibers as conductive support would facilitate the dispersion of bismuth active sites while inhibiting their aggregation and promoting the mass transfer, thus enhancing their electrocatalytic activity and stability. Additionally, nitrogen doping induces electron delocalization in bismuth atoms through metal-support interactions, thus enabling efficient adsorption of intermediates for improving selectivity based on the theoretical calculation. Consequently, Bi@PCNF-500 exhibits the exceptional selectivity and stability across a wide range of potential windows. Notably, its faradaic efficiency(FE) of formate reaches 92.7% in H-cell and94.9% in flow cell, respectively, with good electrocatalytic stability. The in situ characterization and theoretical calculations elucidate the plausible reaction mechanism to obtain basic rules for designing efficient electrocatalyst.

关键词： Carbon dioxide reduction Electron delocalization N-doping Porous carbon nanofiber

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Effect of Texture on the Grain-Size-Dependent Functional Properties of NiTi Shape Memory Alloys and Texture Gradient Design:A Phase Field Study

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Acta Mechanica Solida Sinica 2024年第1期37卷 10-32页

作者： Bo Xu Beihai Huang Chong Wang Qingyuan Wang Failure Mechanics and engineering Disaster Prevention Key Laboratory of Sichuan ProvinceSichuan UniversityChengdu 610065China Department of Mechanical Science and engineering College of Architecture and EnvironmentSichuan UniversityChengdu 610065China key laboratory of Deep underground Science and engineering Ministry of EducationSichuan UniversityChengdu 610065China

Texture is inevitably introduced during the manufacturing of most NiTi shape memory alloys(SMAs),and the textured nanocrystalline NiTi has been extensively employed in ***,the effect of texture,and the joint effect of grain size(GS)and texture on the functional properties of NiTi SMAs and the corresponding microscopic mechanisms have not been clearly understood *** this work,based on the phase field method,the effect of texture on the GS-dependent functional properties of NiTi SMAs,including super-elasticity(SE),one-way shape memory effect(OWSME),and stress-assisted two-way shape memory effect(SATWSME),is investigated,and the corresponding microscopic mechanisms are ***,the samples with discrete geometrical gradients and/or texture gradients are designed to achieve graded functional *** simulation results indicate that the dependence of functional properties on texture is due to the effect of crystallographic orientation on martensite transformation and reorientation,which can lead to different inelastic *** the designed samples with texture gradients,the stress–strain responses of sheets with various textures are different,allowing for the coordination of overall deformation of the sample by combining such sheets,with varying inelastic deformation ***,the overall response of the sample differs from that without texture gradient,leading to the achievement of graded functional *** simulation results and new findings in this work contribute to a deeper understanding of the effects of texture,GS,and their interaction on the functional properties of SMAs,and provide valuable reference for the design and development of SMA-based devices with desired functional properties.

关键词： Phase field NiTi shape memory alloy Texture Grain size Functional property Texture gradient

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