In sub nanometer carbon nanotubes,water exhibits unique dynamic characteristics,and in the high-frequency region of the infrared spectrum,where the stretching vibrations of the internal oxygen-hydrogen(O-H)bonds are c...In sub nanometer carbon nanotubes,water exhibits unique dynamic characteristics,and in the high-frequency region of the infrared spectrum,where the stretching vibrations of the internal oxygen-hydrogen(O-H)bonds are closely related to the hydrogen bonds(H-bonds)network between water molecules.Therefore,it is crucial to analyze the relationship between these two aspects.In this paper,the infrared spectrum and motion characteristics of the stretching vibrations of the O-H bonds in one-dimensional confined water(1DCW)and bulk water(BW)in(6,6)single-walled carbon nanotubes(SWNT)are studied by molecular dynamics simulations.The results show that the stretching vibrations of the two O-H bonds in 1DCW exhibit different frequencies in the infrared spectrum,while the O-H bonds in BW display two identical main frequency peaks.Further analysis using the spring oscillator model reveals that the difference in the stretching amplitude of the O-H bonds is the main factor causing the change in vibration frequency,where an increase in stretching amplitude leads to a decrease in spring stiffness and,consequently,a lower vibration frequency.A more in-depth study found that the interaction of H-bonds between water molecules is the fundamental cause of the increased stretching amplitude and decreased vibration frequency of the O-H bonds.Finally,by analyzing the motion trajectory of the H atoms,the dynamic differences between 1DCW and BW are clearly revealed.These findings provide a new perspective for understanding the behavior of water molecules at the nanoscale and are of significant importance in advancing the development of infrared spectroscopy detection technology.展开更多
The detonation of fuel-rich explosives yields combustible products that persistently burn upon mixing with ambient oxygen,releasing additional energy through a phenomenon known as the afterburning effect.This process ...The detonation of fuel-rich explosives yields combustible products that persistently burn upon mixing with ambient oxygen,releasing additional energy through a phenomenon known as the afterburning effect.This process greatly influences the evolution of confined blast loading and the subsequent structural response,which is crucial in confined blast scenarios.Given the complex nature of the reaction process,accurate analysis of the afterburning effect remains challenging.Previous studies have either overlooked the mechanisms of detonation product combustion or failed to provide experimental validation.This study introduces a three-dimensional model to effectively characterize the combustion of detonation products.The model integrates chemical reaction source terms into the governing equations to consider the combustion processes.Numerical simulations and experimental tests were conducted to analyze the combustion and energy release from the detonation products of fuel-rich explosives in confined spaces.Approximately 50%of the energy was released during the combustion of detonation products in a confined TNT explosion.Although the combustion of these products was much slower than the detonation process,it aligned with the dynamic response of the structure,which enhanced the explosive yield.Excluding afterburning from the analysis reduced the center-point deformation of the structure by 30%.Following the inclusion of afterburning,the simulated quasistatic pressure increased by approximately 45%.Subsequent comparisons highlighted the merits of the proposed approach over conventional methods.This approach eliminates the reliance on empirical parameters,such as the amount and rate of energy release during afterburning,thereby laying the foundation for understanding load evolution in more complex environments,such as ships,buildings,and underground tunnels.展开更多
The structure of water and proton transfer under nanoscale confinement has garnered significant attention due to its crucial role in elucidating various phenomena across multiple scientific disciplines.However,there r...The structure of water and proton transfer under nanoscale confinement has garnered significant attention due to its crucial role in elucidating various phenomena across multiple scientific disciplines.However,there remains a lack of consensus on fundamental properties such as diffusion behavior and the nature of hydrogen bonding in confined environments.In this work,we investigated the influence of confinement on proton transfer in water confined within graphene sheets at various spacings by ab initio molecule dynamic and multiscale analysis with time evolution of structural properties,graph theory and persistent homology.We found that reducing the graphene interlayer distance while maintaining water density close to that of bulk water leads to a decrease in proton transfer frequency.In contrast,reducing the interlayer distance without maintaining bulk-like water density results in an increase in proton transfer frequency.This difference is mainly due to the confinement conditions:when density is unchanged,the hydrogen bond network remains similar with significant layering,while compressive stress that increases density leads to a more planar hydrogen bond network,promoting faster proton transfer.Our findings elucidate the complex relationship between confinement and proton transfer dynamics,with implications for understanding proton transport in confined environments,relevant to energy storage and material design.展开更多
The concept of TNT(Trinitrotoluene,C_7H_5N_3O_6)equivalence is often invoked to evaluate the performance and predict the explosion parameters of different types of explosives.However,due to its low prediction accuracy...The concept of TNT(Trinitrotoluene,C_7H_5N_3O_6)equivalence is often invoked to evaluate the performance and predict the explosion parameters of different types of explosives.However,due to its low prediction accuracy and limited application range,the use of TNT equivalence for predicting explosion parameters in a confined space is rare.Compared with explosions in free fields,the process of explosive energy release in a confined space is closely related to various factors such as oxygen balance,combustible components content,and surrounding oxygen content.Studies have shown that in a confined space,negative oxygen balance explosives react with surrounding oxygen during afterburning,resulting in additional energy release and enhanced blast effects.The mechanism of energy release during afterburning is highly complex,making it challenging to determine the TNT equivalence for blast effects in a confined space.Therefore,this remains an active area of research.In this study,internal blast experiments were conducted using TNT and three other explosives under both air and N_2(Nitrogen)conditions to obtain explosion parameters including blast wave overpressure,quasi-static pressure,and temperature.The influences of oxygen balance and external oxygen content on energy release are analyzed.The author proposes principles for determining TNT equivalence for internal explosions while verifying the accuracy of obtained blast parameters through calculations based on TNT equivalence.These findings can serve as references for predicting blast performance.展开更多
The stress-strain behavior of confined concrete under heating and residual conditions has been preliminarily addressed in previous research;however,its behavior at subsequent cooling temperatures after being heated to...The stress-strain behavior of confined concrete under heating and residual conditions has been preliminarily addressed in previous research;however,its behavior at subsequent cooling temperatures after being heated to peak temperature has yet to be thoroughly investigated.It is crucial for determining confined concrete structures’post-fire performance and burnout resistance.The paper presents the fundamental behavior of the confined concrete constitutive parameters and stress-strain curve at subsequent cooling temperatures after being heated to peak temperature.The study includes the stress-stress relationship of a 200 mm diameter cylinder with two distinct confinement spacings of 60 mm and 120 mm.The constitutive parameters for confined concrete were initially determined for a peak heating temperature of 750℃ and then modified to establish the stress-strain relationship for successive cooling temperatures of 500℃,250℃,and ambient temperature.The study results show that confinement has a considerable impact on compressive strength,stiffness,and ductility at ambient and fire conditions.After being heated to peak temperature,the confined concrete compressive strength recovers during successive cooling temperatures,with the recovery dependent on confinement spacing.The established stress-strain relationship can assist in better comprehending structural performance and capacity degradation for different tie spacings,and is useful for the analysis and design of confined RC(reinforced concrete)elements during and after a fire.展开更多
Nanostructured materials with small particle sizes have been widely used in resistive gas sensors due to their high specific surface area and surface activity.However,phenomena including agglomeration,growth and struc...Nanostructured materials with small particle sizes have been widely used in resistive gas sensors due to their high specific surface area and surface activity.However,phenomena including agglomeration,growth and structural damage of nanostructures are almost inevitable during the processes of device fabrication or sensing tests,which makes it difficult to exert their expected activity.To address this issue,rare earth metal oxide CeO_(2)was chosen as the model material to explore confined nanostructures in resistive gas sensors.The experiment successfully achieves the preparation of confined CeO_(2)nanoparticles film using a pulsed laser deposition combined with rapid annealing technology.It is found that the confined CeO_(2)nanoparticles film enables the efficient detection of volatile organic compound triethylamine,demonstrating a significant response of 20(Ra/Rg)towards 100 ppm triethylamine,a fast response of 2 s,excellent stability and selectivity.By in-situ confinement in porous carbon matrix,dispersion and fixation of CeO_(2)nanoparticles can be achieved,thereby fully utilizing their high surface activity.In addition,the porous carbon matrix can serve as a transport pathway for the target gas molecules and electrons,enabling efficient gas-solid reactions and effective collection of gas sensing signals.More importantly,the confined CeO_(2)nanoparticles film was grown in-situ on commercial alumina flats gas sensing substrate,which can be directly used as sensing layer for gas sensors.Based on first-principles calculations,the triethylamine sensing mechanism of the confined CeO_(2)nanoparticles film was systematically analyzed at the atomic and electronic scale.This study offers new insights into enhancing the gas sensing performance of resistive gas sensors through confined nanostructures design.展开更多
In recent years, significant research efforts have been made to optimize the lithography processes. Liu et al.[1](Nat.Commun, 2024, https://doi.org/10.1038/s41467-024-46743-5)pioneered a new multi-photon lithography t...In recent years, significant research efforts have been made to optimize the lithography processes. Liu et al.[1](Nat.Commun, 2024, https://doi.org/10.1038/s41467-024-46743-5)pioneered a new multi-photon lithography technology in which light field and matter are co-confined, significantly exceeding the limitations of traditional lithography technology. In this news and views, we introduce this work to readers.展开更多
Flexible surface micro-discharge plasma is a non-thermal plasma technique used for treating wounds in a painless way, with significant efficacy for chronic or hard-to-heal wounds. In this study, a confined space was d...Flexible surface micro-discharge plasma is a non-thermal plasma technique used for treating wounds in a painless way, with significant efficacy for chronic or hard-to-heal wounds. In this study, a confined space was designed to simulate wound conditions, with gelatin used to simulate wound tissue. The distinction between open and confined spaces was explored, and the effects of temperature, humidity, discharge power and the gap size within the confined space on the plasma characteristics were analyzed. It was found that temperature, humidity and discharge power are important factors that affect the concentration distribution of active components and the mode transition between ozone and nitrogen oxides. Compared to open space, the concentration of ozone in confined space was relatively lower, which facilitated the formation of nitrogen oxides. In open space, the discharge was dominated by ozone initially. As the temperature,humidity and discharge power increased, nitrogen oxides in the gas-phase products were gradually detected. In confined space, nitrogen oxides can be detected at an early stage and at much higher concentrations than ozone concentration. Furthermore, as the gap of the confined space decreased, the concentration of ozone was observed to decrease while that of nitrate increased, and the rate of this concentration change was further accelerated at higher temperature and higher power. It was shown that ozone concentration decreased from 0.11 to 0.03 μmol and the nitrate concentration increased from 20.5 to 24.5 μmol when the spacing in the confined space was reduced from 5 to 1 mm, the temperature of the external discharge was controlled at 40 ℃, and the discharge power was 12 W. In summary, this study reveals the formation and transformation mechanisms of active substances in air surface micro-discharge plasma within confined space, providing foundational data for its medical applications.展开更多
Sodium-ion batteries with ZnIn_(2)S_(4)(ZIS)anodes promise a high capacity and abundant resources.However,their inherent low conductivity,large volume expansion and sluggish Na+diffusion limit the development of the w...Sodium-ion batteries with ZnIn_(2)S_(4)(ZIS)anodes promise a high capacity and abundant resources.However,their inherent low conductivity,large volume expansion and sluggish Na+diffusion limit the development of the wide-temperature sodium storage.This study pioneers a scalable synthesis of hierarchical hollow structural ZIS/C heterostructure through in situ confined growth of ZIS nanosheets in porous hollow carbon spheres(PHCSs)via a hydrothermal method.This unique structure exhibits abundant heterostructures to facilitate charge transport,rich porous structures to promote electrolyte wettability,efficient space utilization to relieve volume expansion,as well as interconnected carbon networks to ensure framework stability.Consequently,ZIS/C exhibits exceptional cycling stability with 92%capacity retention after 1000 cycles.Notably,ZIS/C demonstrates good wide-temperature performance operating at–50∼90°C,especially,at–30°C with a capacity of 208 mA h g^(−1)at 0.3A g^(−1).The full cell of ZIS/C||Na_(3)V_(2)(PO_(4))_(3)exhibits excellent high-rate capability(178 mA h g^(−1)at 6A g^(−1)).展开更多
The dielectric loss of carbon materials is closely related to the microstructure and the degree of crystallization,and the microstructure modulation of electromagnetic wave absorbing carbon materials is the key to enh...The dielectric loss of carbon materials is closely related to the microstructure and the degree of crystallization,and the microstructure modulation of electromagnetic wave absorbing carbon materials is the key to enhancing absorption properties.In this work,a porous elastic Co@CNF-PDMS composite was prepared by freeze-drying and confined catalysis.The graphitization degree and conductivity loss of carbon nanofibers(CNFs)were regulated by heat treatment temperature and Co catalyst content.The construction of a heterointerface between Co and C enhances the interfacial polarization loss.The Co@CNF-PDMS composite with 4.5 mm achieves the minimum reflection loss(RLmin)of-81.0 dB at 9.9 GHz and RL no higher than-12.1 dB in the whole of the X-band.After applying a load of up to 40% strain and 100 cycles to Co@CNF-PDMS,the dielectric properties of the composite remain stable.With the increase of compression strain,the distribution density of the absorbent increases,and the CNF sheet layer extrusion contact forms a conductive path,which leads to the conductive loss increase,finally,the absorption band moves to a high frequency.The absorption band can be bi-directionally regulated by loading and strain with good stability,which provides a new strategy for the development of intelligent electromagnetic wave absorbing materials.展开更多
Multidimensional confined structure systems are proposed and demonstrated by using MoO_(2)@MO_(2)C(MMC)to enhance the photothermal catalytic performance of the metal sulfides-multidimensional confined structure(TMs-MD...Multidimensional confined structure systems are proposed and demonstrated by using MoO_(2)@MO_(2)C(MMC)to enhance the photothermal catalytic performance of the metal sulfides-multidimensional confined structure(TMs-MDCS).Specifically,the MMC nanoparticles confined to the surface of the ZnIn_(2)S_(4)hollow tube-shell(MMC/HT-ZIS)achieve a hydrogen evolution rate of 9.72 mmol g^(-1)h^(-1),which is 11.2 times higher than that of pure HT-ZIS.Meanwhile,the MnCdS(MCS)nanoparticles are encapsulated within the two-dimensional MMC(2D MMC/MCS)through precise regulation of size and morphology.The 10-MMC/MCS lamellar network demonstrates the highest hydrogen evolution rate of 8.19 mmol g^(-1)-h^(-1).The obtained MMC/TMs-MDCS catalysts exhibit an enhanced photocatalytic hydrogen evolution rate,which can be attributed to the strong synergistic interaction between the multidimensional confinement and the photothermal effects.The confinement space and the strong interfacial relationship within the MMC/TMs-MDCS create abundant channels and active sites that facilitate electron migration and transport.Furthermore,the construction of a confined environment positions these materials as promising candidates for achieving exceptional photothermal catalytic performance,as MMC/TMs-MDCS enhance light absorption through light scattering and reflecting effects.Additionally,the capacity of MMC/TMsMDCS to convert solar light into thermal energy significantly reduces the activation energy of the reaction,thereby facilitating reaction kinetics and accelerating the separation and transport of photogenerated carriers.This work provides valuable insights for the development of highly efficient photothermal catalytic water-splitting systems for hydrogen production using multidimensional confined catalysts.展开更多
TiNb_(2)O_(7)has been emerged as one of the most promising electrode materials for high-energy lithium-ion batteries.However,limited by the slow electron/ion transport kinetics,and insufficient active sites in the bul...TiNb_(2)O_(7)has been emerged as one of the most promising electrode materials for high-energy lithium-ion batteries.However,limited by the slow electron/ion transport kinetics,and insufficient active sites in the bulk structure,the TiNb_(2)O_(7)electrode still suffers from unsatisfactory lithium storage performance.Herein,we demonstrate a spatially confined strategy toward a novel TiNb_(2)O_(7)-NMC/MXene composite through a triblock copolymer-directed one-pot solvothermal route,where TiNb_(2)O_(7)quantum dots with a particle size of 2-3 nm are evenly embedded into N-doped mesoporous carbon(NMC)and Ti_(3)C_(2)T_(X)MXene.Impressively,the as-prepared TiNb_(2)O_(7)-NMC/MXene anode exhibits a high reversible capacity(486.2 mAh g^(-1)at 0.1 A g^(-1)after 100 cycles)and long cycle lifespan(363.4 mAh g^(-1)at ss1 A g^(-1)after 500 cycles).Both experimental and theorical results further demonstrate that such a superior lithium storage performance is mainly ascribed to the synergistic effect among 0D TiNb_(2)O_(7)quantum dots,2D Ti_(3)C_(2)T_(X)MXene nanosheets,and N-doped mesoporous carbon.The strategy presented also opens up new horizon for space-confined preparation of high-performance electrode materials.展开更多
The conformational and dynamical properties of a long semi-flexible active polymer chain confined in a circular cavity are studied by using Langevin dynamics simulation method.Results show that the steady radius of gy...The conformational and dynamical properties of a long semi-flexible active polymer chain confined in a circular cavity are studied by using Langevin dynamics simulation method.Results show that the steady radius of gyration of the polymer decreases monotonically with increasing the active force.Interestingly,the polymer forms stable compact spiral with directional rotation at the steady state when the active force is large.Both the radius of gyration and the angular velocity of the spiral are nearly independent of the cavity size,but show scaling relations with the active force and the polymer length.It is further found that the formation of the stable compact spiral in most cases is a two-step relaxation process,where the polymer first forms a metastable swelling quasi spiral and then transforms into the stable compacted spiral near the wall of the cavity.The relaxation time is mainly determined by the transformation of the swelling quasi spiral,and shows remarkable dependence on the size of the cavity.Specially,when the circumference of the circular is nearly equivalent to the polymer length,it is difficult for the polymer to form the compacted spiral,leading to a large relaxation time.The underlying mechanism of the formation of the compacted spiral is revealed.展开更多
Active matter exhibits collective motions at various scales.Geometric confinement has been identified as an effective way to control and manipulate active fluids,with much attention given to external factors.However,t...Active matter exhibits collective motions at various scales.Geometric confinement has been identified as an effective way to control and manipulate active fluids,with much attention given to external factors.However,the impact of the inherent properties of active particles on collective motion under confined conditions remains elusive.Here,we use a highly tunable active nematics model to study active systems under confinement,focusing on the effect of the self-driven speed of active particles.We identify three distinct states characterized by unique particle and flow fields within confined active nematic systems,among which circular rotation emerges as a collective motion involving rotational movement in both particle and flow fields.The theoretical phase diagram shows that increasing the self-driven speed of active particles significantly enhances the region of the circular rotation state and improves its stability.Our results provide insights into the formation of high quality vortices in confined active nematic systems.展开更多
Metal-organic frameworks(MOFs)serve as highly effective hosts for ultrasmall metal species,creating advanced nanocatalysts with superior catalytic performance,stability,and selective activity.The synergistic interplay...Metal-organic frameworks(MOFs)serve as highly effective hosts for ultrasmall metal species,creating advanced nanocatalysts with superior catalytic performance,stability,and selective activity.The synergistic interplay between metal species confined within MOF nanopores and their active sites enhances catalytic efficiency in CO_(2)hydrogenation reactions.Herein,recent advancements in synthesizing metal-confined MOFs are discussed,along with their applications in catalyzing CO_(2)conversion through various methods such as photocatalysis,thermal catalysis,and photothermal catalysis.Additionally,we further emphasize the fundamental principles and factors that influence various types of catalytic CO_(2)hydrogenation reactions,while offering insights into future research directions in this dynamic field.展开更多
Developing high performance electrocatalysts for the cathodic oxygen reduction reaction(ORR)is essential for the widespread application of fuel cells.Herein,a promising Pt_(2)NiCo atomic ordered ternary intermetallic ...Developing high performance electrocatalysts for the cathodic oxygen reduction reaction(ORR)is essential for the widespread application of fuel cells.Herein,a promising Pt_(2)NiCo atomic ordered ternary intermetallic compound with N-doped carbon layer coating(o-Pt_(2)NiCo@NC)has been synthesized via a facile method and applied in acidic ORR.The confinement effect provided by the carbon layer not only inhibits the agglomeration and sintering of intermetallic nanoparticles during high temperature process but also provides adequate protection for the nanoparticles,mitigating the aggregation,detachment and poisoning of nanoparticles during the electrochemical process.As a result,the o-Pt_(2)NiCo@NC demonstrates a mass activity(MA)and specific activity(SA)of 0.65 A/mgPt and 1.41mA/cm_(Pt) ^(2) in 0.1mol/L HClO_(4),respectively.In addition,after 30,000 potential cycles from 0.6 V to 1.0 V,the MA of o-Pt_(2)NiCo@NC shows much lower decrease than the disordered Pt_(2)NiCo alloy and Pt/C.Even cycling at high potential cycles of 1.5 V for 10,000 cycles,the MA still retains∼70%,demonstrating superior long-term durability.Furthermore,the o-Pt_(2)NiCo@NC also exhibits strong tolerance to CO,SO_(x),and PO_(x) molecules in toxicity tolerance tests.The strategy in this work provides a novel insight for the development of ORR catalysts with high catalytic activity,durability and toxicity tolerance.展开更多
Precise regulation of atomic and electronic structures of two-dimensional tungsten disulfide(WS_(2))is significant for rational design of high-performance and low-cost catalyst for acetylene hydrogenation to ethylene(...Precise regulation of atomic and electronic structures of two-dimensional tungsten disulfide(WS_(2))is significant for rational design of high-performance and low-cost catalyst for acetylene hydrogenation to ethylene(AHE),yet remains a major challenge.Herein,we report that by substituting a W atom of WS_(2) with a series of transition metal atoms,sulfur vacancy-confined Cu in the WS_(2) basal plane(Cu@WS_(2)-Sv)is theoretically screened as a superior non-noble metal-based catalyst with higher activity,selectivity,and stability for the AHE than other candidates.The co-adsorption of C_(2)H_(2) and H_(2) and hydrogenation of C_(2)H_(3)^(*) to C_(2)H_(4)^(*) are revealed as the key steps establishing a volcano-like activity trend among the candidates,which present Cu@WS_(2)-Sv as the optimum catalyst combined with molecular dynamics and reaction kinetics analyses.The kinetically more favorable desorption of C_(2)H_(4) than the over hydrogenation path validates a higher selectivity toward C_(2)H_(4) over C_(2)H_(6).Furthermore,a machine-learning model reveals the significant effect of d-electron number and electronegativity of the metal heteroatoms in modulating the AHE activity.展开更多
Directly modulated 850-nm vertical-cavity surface-emitting lasers(VCSELs)with the advantages of low cost,high modulation speed,good reliability,and low power consumption,are the key sources in the optical interconnect...Directly modulated 850-nm vertical-cavity surface-emitting lasers(VCSELs)with the advantages of low cost,high modulation speed,good reliability,and low power consumption,are the key sources in the optical interconnects with multimode fibers for the supercomputers,data centers,and machine learning applications[1−3].Typically,non-return-tozero(NRZ)modulation format is used.展开更多
Macrocycle confinement induced vip near-infrared(NIR)luminescence was research hotspot currently.Here in,we reported a cucurbit[7]uril(CB[7])confined 3,7-bis((E)-2-(pyridin-4-yl)vinyl)-10-Hphenothiazine bridged bis(...Macrocycle confinement induced vip near-infrared(NIR)luminescence was research hotspot currently.Here in,we reported a cucurbit[7]uril(CB[7])confined 3,7-bis((E)-2-(pyridin-4-yl)vinyl)-10-Hphenothiazine bridged bis(4-(4-bromophenyl)pyridine)(G),which not only boosted its NIR luminescence but also realized detection of HClO/ClO^(-)in living cells and lysosome imaging.Fluorescence spectroscopy experiments were performed to calculate the detection ability of probe G to HClO/ClO^(-)up to 147 nmol/L.As compared with G,supramolecular probe G■CB[7]formed after encapsulated by CB[7],the detection ability towards HClO/ClO^(-)was improved to 24 nmol/L which was ascribe to the macrocycle CB[7]confinement increasing the fluorescence intensity to 103 folds.Accompanying the excitation wavelength changing,the fluorescence red-shifted to 820 nm when excited by 570 nm light,which was used to NIR lysosome imaging.Meanwhile,the supramolecular assembly G■CB[7]was also successfully used to highly sense to exogenous HClO/ClO^(-)in RAW 264.7 cells and live animal.展开更多
In the process of shield tunneling through soft soil layers,the presence of confined water ahead poses a significant threat to the stability of the tunnel face.Therefore,it is crucial to consider the impact of confine...In the process of shield tunneling through soft soil layers,the presence of confined water ahead poses a significant threat to the stability of the tunnel face.Therefore,it is crucial to consider the impact of confined water on the limit support pressure of the tunnel face.This study employed the finite element method(FEM)to analyze the limit support pressure of shield tunnel face instability within a pressurized water-containing layer.Subsequently,a multiple linear regression approach was applied to derive a concise solution formula for the limit support pressure,incorporating various influencing factors.The analysis yields the following conclusions:1)The influence of confined water on the instability mode of the tunnel face in soft soil layers makes the displacement response of the strata not significant when the face is unstable;2)The limit support pressure increases approximately linearly with the pressure head,shield tunnel diameter,and tunnel burial depth.And inversely proportional to the thickness of the impermeable layer,soil cohesion and internal friction angle;3)Through an engineering case study analysis,the results align well with those obtained from traditional theoretical methods,thereby validating the rationality of the equations proposed in this paper.Furthermore,the proposed equations overcome the limitation of traditional theoretical approaches considering the influence of changes in impermeable layer thickness.It can accurately depict the dynamic variation in the required limit support pressure to maintain the stability of the tunnel face during shield tunneling,thus better reflecting engineering reality.展开更多
基金Supported by the Natural Science Foundation of China(51705326,52075339)。
文摘In sub nanometer carbon nanotubes,water exhibits unique dynamic characteristics,and in the high-frequency region of the infrared spectrum,where the stretching vibrations of the internal oxygen-hydrogen(O-H)bonds are closely related to the hydrogen bonds(H-bonds)network between water molecules.Therefore,it is crucial to analyze the relationship between these two aspects.In this paper,the infrared spectrum and motion characteristics of the stretching vibrations of the O-H bonds in one-dimensional confined water(1DCW)and bulk water(BW)in(6,6)single-walled carbon nanotubes(SWNT)are studied by molecular dynamics simulations.The results show that the stretching vibrations of the two O-H bonds in 1DCW exhibit different frequencies in the infrared spectrum,while the O-H bonds in BW display two identical main frequency peaks.Further analysis using the spring oscillator model reveals that the difference in the stretching amplitude of the O-H bonds is the main factor causing the change in vibration frequency,where an increase in stretching amplitude leads to a decrease in spring stiffness and,consequently,a lower vibration frequency.A more in-depth study found that the interaction of H-bonds between water molecules is the fundamental cause of the increased stretching amplitude and decreased vibration frequency of the O-H bonds.Finally,by analyzing the motion trajectory of the H atoms,the dynamic differences between 1DCW and BW are clearly revealed.These findings provide a new perspective for understanding the behavior of water molecules at the nanoscale and are of significant importance in advancing the development of infrared spectroscopy detection technology.
基金supported by the National Natural Science Foundation of China(Grant Nos.52171318 and 12202329)Joint Foundation of the Ministry of Education(Grant No.8091B022105)。
文摘The detonation of fuel-rich explosives yields combustible products that persistently burn upon mixing with ambient oxygen,releasing additional energy through a phenomenon known as the afterburning effect.This process greatly influences the evolution of confined blast loading and the subsequent structural response,which is crucial in confined blast scenarios.Given the complex nature of the reaction process,accurate analysis of the afterburning effect remains challenging.Previous studies have either overlooked the mechanisms of detonation product combustion or failed to provide experimental validation.This study introduces a three-dimensional model to effectively characterize the combustion of detonation products.The model integrates chemical reaction source terms into the governing equations to consider the combustion processes.Numerical simulations and experimental tests were conducted to analyze the combustion and energy release from the detonation products of fuel-rich explosives in confined spaces.Approximately 50%of the energy was released during the combustion of detonation products in a confined TNT explosion.Although the combustion of these products was much slower than the detonation process,it aligned with the dynamic response of the structure,which enhanced the explosive yield.Excluding afterburning from the analysis reduced the center-point deformation of the structure by 30%.Following the inclusion of afterburning,the simulated quasistatic pressure increased by approximately 45%.Subsequent comparisons highlighted the merits of the proposed approach over conventional methods.This approach eliminates the reliance on empirical parameters,such as the amount and rate of energy release during afterburning,thereby laying the foundation for understanding load evolution in more complex environments,such as ships,buildings,and underground tunnels.
基金supported by the Natural Science Foundation of Xiamen,China(3502Z202472001)the National Natural Science Foundation of China(22402163,22021001,21925404,T2293692,and 22361132532).
文摘The structure of water and proton transfer under nanoscale confinement has garnered significant attention due to its crucial role in elucidating various phenomena across multiple scientific disciplines.However,there remains a lack of consensus on fundamental properties such as diffusion behavior and the nature of hydrogen bonding in confined environments.In this work,we investigated the influence of confinement on proton transfer in water confined within graphene sheets at various spacings by ab initio molecule dynamic and multiscale analysis with time evolution of structural properties,graph theory and persistent homology.We found that reducing the graphene interlayer distance while maintaining water density close to that of bulk water leads to a decrease in proton transfer frequency.In contrast,reducing the interlayer distance without maintaining bulk-like water density results in an increase in proton transfer frequency.This difference is mainly due to the confinement conditions:when density is unchanged,the hydrogen bond network remains similar with significant layering,while compressive stress that increases density leads to a more planar hydrogen bond network,promoting faster proton transfer.Our findings elucidate the complex relationship between confinement and proton transfer dynamics,with implications for understanding proton transport in confined environments,relevant to energy storage and material design.
文摘The concept of TNT(Trinitrotoluene,C_7H_5N_3O_6)equivalence is often invoked to evaluate the performance and predict the explosion parameters of different types of explosives.However,due to its low prediction accuracy and limited application range,the use of TNT equivalence for predicting explosion parameters in a confined space is rare.Compared with explosions in free fields,the process of explosive energy release in a confined space is closely related to various factors such as oxygen balance,combustible components content,and surrounding oxygen content.Studies have shown that in a confined space,negative oxygen balance explosives react with surrounding oxygen during afterburning,resulting in additional energy release and enhanced blast effects.The mechanism of energy release during afterburning is highly complex,making it challenging to determine the TNT equivalence for blast effects in a confined space.Therefore,this remains an active area of research.In this study,internal blast experiments were conducted using TNT and three other explosives under both air and N_2(Nitrogen)conditions to obtain explosion parameters including blast wave overpressure,quasi-static pressure,and temperature.The influences of oxygen balance and external oxygen content on energy release are analyzed.The author proposes principles for determining TNT equivalence for internal explosions while verifying the accuracy of obtained blast parameters through calculations based on TNT equivalence.These findings can serve as references for predicting blast performance.
文摘The stress-strain behavior of confined concrete under heating and residual conditions has been preliminarily addressed in previous research;however,its behavior at subsequent cooling temperatures after being heated to peak temperature has yet to be thoroughly investigated.It is crucial for determining confined concrete structures’post-fire performance and burnout resistance.The paper presents the fundamental behavior of the confined concrete constitutive parameters and stress-strain curve at subsequent cooling temperatures after being heated to peak temperature.The study includes the stress-stress relationship of a 200 mm diameter cylinder with two distinct confinement spacings of 60 mm and 120 mm.The constitutive parameters for confined concrete were initially determined for a peak heating temperature of 750℃ and then modified to establish the stress-strain relationship for successive cooling temperatures of 500℃,250℃,and ambient temperature.The study results show that confinement has a considerable impact on compressive strength,stiffness,and ductility at ambient and fire conditions.After being heated to peak temperature,the confined concrete compressive strength recovers during successive cooling temperatures,with the recovery dependent on confinement spacing.The established stress-strain relationship can assist in better comprehending structural performance and capacity degradation for different tie spacings,and is useful for the analysis and design of confined RC(reinforced concrete)elements during and after a fire.
基金Project supported by the Jiangxi Provincial Natural Science Foundation(20224BAB212026,20224BAB214026,20242BAB23008)National Natural Science Foundation of China(62361033)。
文摘Nanostructured materials with small particle sizes have been widely used in resistive gas sensors due to their high specific surface area and surface activity.However,phenomena including agglomeration,growth and structural damage of nanostructures are almost inevitable during the processes of device fabrication or sensing tests,which makes it difficult to exert their expected activity.To address this issue,rare earth metal oxide CeO_(2)was chosen as the model material to explore confined nanostructures in resistive gas sensors.The experiment successfully achieves the preparation of confined CeO_(2)nanoparticles film using a pulsed laser deposition combined with rapid annealing technology.It is found that the confined CeO_(2)nanoparticles film enables the efficient detection of volatile organic compound triethylamine,demonstrating a significant response of 20(Ra/Rg)towards 100 ppm triethylamine,a fast response of 2 s,excellent stability and selectivity.By in-situ confinement in porous carbon matrix,dispersion and fixation of CeO_(2)nanoparticles can be achieved,thereby fully utilizing their high surface activity.In addition,the porous carbon matrix can serve as a transport pathway for the target gas molecules and electrons,enabling efficient gas-solid reactions and effective collection of gas sensing signals.More importantly,the confined CeO_(2)nanoparticles film was grown in-situ on commercial alumina flats gas sensing substrate,which can be directly used as sensing layer for gas sensors.Based on first-principles calculations,the triethylamine sensing mechanism of the confined CeO_(2)nanoparticles film was systematically analyzed at the atomic and electronic scale.This study offers new insights into enhancing the gas sensing performance of resistive gas sensors through confined nanostructures design.
基金supported by Xishan-Tsinghua University Industry University Research Deep Integration Special Projectby Beijing Natural Science Foundation–Xiaomi Innovation Joint Fund (Grant No. L233009)by National Natural Science Foundation of China under Grant No. 62374099。
文摘In recent years, significant research efforts have been made to optimize the lithography processes. Liu et al.[1](Nat.Commun, 2024, https://doi.org/10.1038/s41467-024-46743-5)pioneered a new multi-photon lithography technology in which light field and matter are co-confined, significantly exceeding the limitations of traditional lithography technology. In this news and views, we introduce this work to readers.
基金supported by Postgraduate Research&Practice Innovation Program of Jiangsu Province (No. 1003016001)。
文摘Flexible surface micro-discharge plasma is a non-thermal plasma technique used for treating wounds in a painless way, with significant efficacy for chronic or hard-to-heal wounds. In this study, a confined space was designed to simulate wound conditions, with gelatin used to simulate wound tissue. The distinction between open and confined spaces was explored, and the effects of temperature, humidity, discharge power and the gap size within the confined space on the plasma characteristics were analyzed. It was found that temperature, humidity and discharge power are important factors that affect the concentration distribution of active components and the mode transition between ozone and nitrogen oxides. Compared to open space, the concentration of ozone in confined space was relatively lower, which facilitated the formation of nitrogen oxides. In open space, the discharge was dominated by ozone initially. As the temperature,humidity and discharge power increased, nitrogen oxides in the gas-phase products were gradually detected. In confined space, nitrogen oxides can be detected at an early stage and at much higher concentrations than ozone concentration. Furthermore, as the gap of the confined space decreased, the concentration of ozone was observed to decrease while that of nitrate increased, and the rate of this concentration change was further accelerated at higher temperature and higher power. It was shown that ozone concentration decreased from 0.11 to 0.03 μmol and the nitrate concentration increased from 20.5 to 24.5 μmol when the spacing in the confined space was reduced from 5 to 1 mm, the temperature of the external discharge was controlled at 40 ℃, and the discharge power was 12 W. In summary, this study reveals the formation and transformation mechanisms of active substances in air surface micro-discharge plasma within confined space, providing foundational data for its medical applications.
基金supported by the National Natural Science Foundation of China(U23B2075)the Natural Science Foundation of Shandong Province(ZR202111290333)the China Postdoctoral Science Foundation(2023M730640,2024M750490).
文摘Sodium-ion batteries with ZnIn_(2)S_(4)(ZIS)anodes promise a high capacity and abundant resources.However,their inherent low conductivity,large volume expansion and sluggish Na+diffusion limit the development of the wide-temperature sodium storage.This study pioneers a scalable synthesis of hierarchical hollow structural ZIS/C heterostructure through in situ confined growth of ZIS nanosheets in porous hollow carbon spheres(PHCSs)via a hydrothermal method.This unique structure exhibits abundant heterostructures to facilitate charge transport,rich porous structures to promote electrolyte wettability,efficient space utilization to relieve volume expansion,as well as interconnected carbon networks to ensure framework stability.Consequently,ZIS/C exhibits exceptional cycling stability with 92%capacity retention after 1000 cycles.Notably,ZIS/C demonstrates good wide-temperature performance operating at–50∼90°C,especially,at–30°C with a capacity of 208 mA h g^(−1)at 0.3A g^(−1).The full cell of ZIS/C||Na_(3)V_(2)(PO_(4))_(3)exhibits excellent high-rate capability(178 mA h g^(−1)at 6A g^(−1)).
基金financially supported by the National Natural Science Foundation of China(No.52231007)the Natural Science Foundation of Shaanxi Province(No.2022JM-248)+1 种基金the Creative Research Foundation of the Science and Technology on Thermostructural Composite Materials Laboratorythe Doctoral Scientific Research Foundation of Shaanxi University of Science&Technology(No.BJ16-06).
文摘The dielectric loss of carbon materials is closely related to the microstructure and the degree of crystallization,and the microstructure modulation of electromagnetic wave absorbing carbon materials is the key to enhancing absorption properties.In this work,a porous elastic Co@CNF-PDMS composite was prepared by freeze-drying and confined catalysis.The graphitization degree and conductivity loss of carbon nanofibers(CNFs)were regulated by heat treatment temperature and Co catalyst content.The construction of a heterointerface between Co and C enhances the interfacial polarization loss.The Co@CNF-PDMS composite with 4.5 mm achieves the minimum reflection loss(RLmin)of-81.0 dB at 9.9 GHz and RL no higher than-12.1 dB in the whole of the X-band.After applying a load of up to 40% strain and 100 cycles to Co@CNF-PDMS,the dielectric properties of the composite remain stable.With the increase of compression strain,the distribution density of the absorbent increases,and the CNF sheet layer extrusion contact forms a conductive path,which leads to the conductive loss increase,finally,the absorption band moves to a high frequency.The absorption band can be bi-directionally regulated by loading and strain with good stability,which provides a new strategy for the development of intelligent electromagnetic wave absorbing materials.
基金supported by the Postgraduate Education Reform Project of Shandong Province(SDYAL2023032)the National Key Research and Development Program(2021YFB3500102)。
文摘Multidimensional confined structure systems are proposed and demonstrated by using MoO_(2)@MO_(2)C(MMC)to enhance the photothermal catalytic performance of the metal sulfides-multidimensional confined structure(TMs-MDCS).Specifically,the MMC nanoparticles confined to the surface of the ZnIn_(2)S_(4)hollow tube-shell(MMC/HT-ZIS)achieve a hydrogen evolution rate of 9.72 mmol g^(-1)h^(-1),which is 11.2 times higher than that of pure HT-ZIS.Meanwhile,the MnCdS(MCS)nanoparticles are encapsulated within the two-dimensional MMC(2D MMC/MCS)through precise regulation of size and morphology.The 10-MMC/MCS lamellar network demonstrates the highest hydrogen evolution rate of 8.19 mmol g^(-1)-h^(-1).The obtained MMC/TMs-MDCS catalysts exhibit an enhanced photocatalytic hydrogen evolution rate,which can be attributed to the strong synergistic interaction between the multidimensional confinement and the photothermal effects.The confinement space and the strong interfacial relationship within the MMC/TMs-MDCS create abundant channels and active sites that facilitate electron migration and transport.Furthermore,the construction of a confined environment positions these materials as promising candidates for achieving exceptional photothermal catalytic performance,as MMC/TMs-MDCS enhance light absorption through light scattering and reflecting effects.Additionally,the capacity of MMC/TMsMDCS to convert solar light into thermal energy significantly reduces the activation energy of the reaction,thereby facilitating reaction kinetics and accelerating the separation and transport of photogenerated carriers.This work provides valuable insights for the development of highly efficient photothermal catalytic water-splitting systems for hydrogen production using multidimensional confined catalysts.
基金support from the Natural Science Foundation of Shanghai(23ZR1423800),Shuguang Program supported by Shanghai Education Development Foundation and Shanghai Municipal Education Commission(18SG35)Open Research Fund of Shanghai Key Laboratory of Green Chemistry and Chemical Processes(East China Normal University)Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education),Nankai University.
文摘TiNb_(2)O_(7)has been emerged as one of the most promising electrode materials for high-energy lithium-ion batteries.However,limited by the slow electron/ion transport kinetics,and insufficient active sites in the bulk structure,the TiNb_(2)O_(7)electrode still suffers from unsatisfactory lithium storage performance.Herein,we demonstrate a spatially confined strategy toward a novel TiNb_(2)O_(7)-NMC/MXene composite through a triblock copolymer-directed one-pot solvothermal route,where TiNb_(2)O_(7)quantum dots with a particle size of 2-3 nm are evenly embedded into N-doped mesoporous carbon(NMC)and Ti_(3)C_(2)T_(X)MXene.Impressively,the as-prepared TiNb_(2)O_(7)-NMC/MXene anode exhibits a high reversible capacity(486.2 mAh g^(-1)at 0.1 A g^(-1)after 100 cycles)and long cycle lifespan(363.4 mAh g^(-1)at ss1 A g^(-1)after 500 cycles).Both experimental and theorical results further demonstrate that such a superior lithium storage performance is mainly ascribed to the synergistic effect among 0D TiNb_(2)O_(7)quantum dots,2D Ti_(3)C_(2)T_(X)MXene nanosheets,and N-doped mesoporous carbon.The strategy presented also opens up new horizon for space-confined preparation of high-performance electrode materials.
基金supported by the Zhejiang Provincial Natural Science Foundation of China(No.LY20A040004)the National Natural Science Foundation of China(Nos.22203060 and 11974305).
文摘The conformational and dynamical properties of a long semi-flexible active polymer chain confined in a circular cavity are studied by using Langevin dynamics simulation method.Results show that the steady radius of gyration of the polymer decreases monotonically with increasing the active force.Interestingly,the polymer forms stable compact spiral with directional rotation at the steady state when the active force is large.Both the radius of gyration and the angular velocity of the spiral are nearly independent of the cavity size,but show scaling relations with the active force and the polymer length.It is further found that the formation of the stable compact spiral in most cases is a two-step relaxation process,where the polymer first forms a metastable swelling quasi spiral and then transforms into the stable compacted spiral near the wall of the cavity.The relaxation time is mainly determined by the transformation of the swelling quasi spiral,and shows remarkable dependence on the size of the cavity.Specially,when the circumference of the circular is nearly equivalent to the polymer length,it is difficult for the polymer to form the compacted spiral,leading to a large relaxation time.The underlying mechanism of the formation of the compacted spiral is revealed.
基金supported by the National Key Research and Development Program of China under Grant No.2022YFA1405000Innovation Program for Quantum Science and Technology under Grant No.2024ZD0300101the National Natural Science Foundation of China under Grant Nos.12274212,12174184,12347102。
文摘Active matter exhibits collective motions at various scales.Geometric confinement has been identified as an effective way to control and manipulate active fluids,with much attention given to external factors.However,the impact of the inherent properties of active particles on collective motion under confined conditions remains elusive.Here,we use a highly tunable active nematics model to study active systems under confinement,focusing on the effect of the self-driven speed of active particles.We identify three distinct states characterized by unique particle and flow fields within confined active nematic systems,among which circular rotation emerges as a collective motion involving rotational movement in both particle and flow fields.The theoretical phase diagram shows that increasing the self-driven speed of active particles significantly enhances the region of the circular rotation state and improves its stability.Our results provide insights into the formation of high quality vortices in confined active nematic systems.
文摘Metal-organic frameworks(MOFs)serve as highly effective hosts for ultrasmall metal species,creating advanced nanocatalysts with superior catalytic performance,stability,and selective activity.The synergistic interplay between metal species confined within MOF nanopores and their active sites enhances catalytic efficiency in CO_(2)hydrogenation reactions.Herein,recent advancements in synthesizing metal-confined MOFs are discussed,along with their applications in catalyzing CO_(2)conversion through various methods such as photocatalysis,thermal catalysis,and photothermal catalysis.Additionally,we further emphasize the fundamental principles and factors that influence various types of catalytic CO_(2)hydrogenation reactions,while offering insights into future research directions in this dynamic field.
基金supported by the National Natural Science Foundation(No.22279036)the Innovation and Talent Recruitment Base of New Energy Chemistry and Device(No.B21003).
文摘Developing high performance electrocatalysts for the cathodic oxygen reduction reaction(ORR)is essential for the widespread application of fuel cells.Herein,a promising Pt_(2)NiCo atomic ordered ternary intermetallic compound with N-doped carbon layer coating(o-Pt_(2)NiCo@NC)has been synthesized via a facile method and applied in acidic ORR.The confinement effect provided by the carbon layer not only inhibits the agglomeration and sintering of intermetallic nanoparticles during high temperature process but also provides adequate protection for the nanoparticles,mitigating the aggregation,detachment and poisoning of nanoparticles during the electrochemical process.As a result,the o-Pt_(2)NiCo@NC demonstrates a mass activity(MA)and specific activity(SA)of 0.65 A/mgPt and 1.41mA/cm_(Pt) ^(2) in 0.1mol/L HClO_(4),respectively.In addition,after 30,000 potential cycles from 0.6 V to 1.0 V,the MA of o-Pt_(2)NiCo@NC shows much lower decrease than the disordered Pt_(2)NiCo alloy and Pt/C.Even cycling at high potential cycles of 1.5 V for 10,000 cycles,the MA still retains∼70%,demonstrating superior long-term durability.Furthermore,the o-Pt_(2)NiCo@NC also exhibits strong tolerance to CO,SO_(x),and PO_(x) molecules in toxicity tolerance tests.The strategy in this work provides a novel insight for the development of ORR catalysts with high catalytic activity,durability and toxicity tolerance.
文摘Precise regulation of atomic and electronic structures of two-dimensional tungsten disulfide(WS_(2))is significant for rational design of high-performance and low-cost catalyst for acetylene hydrogenation to ethylene(AHE),yet remains a major challenge.Herein,we report that by substituting a W atom of WS_(2) with a series of transition metal atoms,sulfur vacancy-confined Cu in the WS_(2) basal plane(Cu@WS_(2)-Sv)is theoretically screened as a superior non-noble metal-based catalyst with higher activity,selectivity,and stability for the AHE than other candidates.The co-adsorption of C_(2)H_(2) and H_(2) and hydrogenation of C_(2)H_(3)^(*) to C_(2)H_(4)^(*) are revealed as the key steps establishing a volcano-like activity trend among the candidates,which present Cu@WS_(2)-Sv as the optimum catalyst combined with molecular dynamics and reaction kinetics analyses.The kinetically more favorable desorption of C_(2)H_(4) than the over hydrogenation path validates a higher selectivity toward C_(2)H_(4) over C_(2)H_(6).Furthermore,a machine-learning model reveals the significant effect of d-electron number and electronegativity of the metal heteroatoms in modulating the AHE activity.
基金supported by the National Natural Science Foundation of China(Nos.62075209,62275243,and 61675193)the Beijing Natural Science Foundation(No.Z200006).
文摘Directly modulated 850-nm vertical-cavity surface-emitting lasers(VCSELs)with the advantages of low cost,high modulation speed,good reliability,and low power consumption,are the key sources in the optical interconnects with multimode fibers for the supercomputers,data centers,and machine learning applications[1−3].Typically,non-return-tozero(NRZ)modulation format is used.
基金financially supported by the National Natural Science Foundation of China(No.22131008)Liaocheng University Start-up Fund for Doctoral Scientific Research(No.318052327)。
文摘Macrocycle confinement induced vip near-infrared(NIR)luminescence was research hotspot currently.Here in,we reported a cucurbit[7]uril(CB[7])confined 3,7-bis((E)-2-(pyridin-4-yl)vinyl)-10-Hphenothiazine bridged bis(4-(4-bromophenyl)pyridine)(G),which not only boosted its NIR luminescence but also realized detection of HClO/ClO^(-)in living cells and lysosome imaging.Fluorescence spectroscopy experiments were performed to calculate the detection ability of probe G to HClO/ClO^(-)up to 147 nmol/L.As compared with G,supramolecular probe G■CB[7]formed after encapsulated by CB[7],the detection ability towards HClO/ClO^(-)was improved to 24 nmol/L which was ascribe to the macrocycle CB[7]confinement increasing the fluorescence intensity to 103 folds.Accompanying the excitation wavelength changing,the fluorescence red-shifted to 820 nm when excited by 570 nm light,which was used to NIR lysosome imaging.Meanwhile,the supramolecular assembly G■CB[7]was also successfully used to highly sense to exogenous HClO/ClO^(-)in RAW 264.7 cells and live animal.
基金Project(ZDRW-ZS-2021-3)supported by the Key Deployment Projects of Chinese Academy of SciencesProjects(52179116,51991392)supported by the National Natural Science Foundation of China。
文摘In the process of shield tunneling through soft soil layers,the presence of confined water ahead poses a significant threat to the stability of the tunnel face.Therefore,it is crucial to consider the impact of confined water on the limit support pressure of the tunnel face.This study employed the finite element method(FEM)to analyze the limit support pressure of shield tunnel face instability within a pressurized water-containing layer.Subsequently,a multiple linear regression approach was applied to derive a concise solution formula for the limit support pressure,incorporating various influencing factors.The analysis yields the following conclusions:1)The influence of confined water on the instability mode of the tunnel face in soft soil layers makes the displacement response of the strata not significant when the face is unstable;2)The limit support pressure increases approximately linearly with the pressure head,shield tunnel diameter,and tunnel burial depth.And inversely proportional to the thickness of the impermeable layer,soil cohesion and internal friction angle;3)Through an engineering case study analysis,the results align well with those obtained from traditional theoretical methods,thereby validating the rationality of the equations proposed in this paper.Furthermore,the proposed equations overcome the limitation of traditional theoretical approaches considering the influence of changes in impermeable layer thickness.It can accurately depict the dynamic variation in the required limit support pressure to maintain the stability of the tunnel face during shield tunneling,thus better reflecting engineering reality.
