Grouting is a major method used to prevent water and mud inrush in tunnels and underground engineering. In this paper, the current situation of control and prevention of water and mud inrush is summarized and recent a...Grouting is a major method used to prevent water and mud inrush in tunnels and underground engineering. In this paper, the current situation of control and prevention of water and mud inrush is summarized and recent advances in relevant theories, grout/equipment, and critical techniques are introduced. The time-variant equations of grout viscosity at different volumetric ratios were obtained based on the constitutive relation of typical fast curing grouts. A large-scale dynamic grouting model testing system （4000 mm × 2000 mm × 5 mm） was developed, and the diffusions of cement and fast curing grouts in dynamic water grouting were investigated. The results reveal that the diffusions of cement grouts and fast curing grouts are U-shaped and asymmetric elliptical, respectively. A multi-parameter real-time monitoring system （＆#981; = 1.5 m, h = 1.2 m） was developed for the grouting process to study the diffusion and reinforcement mechanism of grouting in water-rich faulted zone. A high early strength cream-type reinforcing/plugging grout, a high permeability nano-scale silica gel grout, and a high-expansion filling grout were proposed for the control of water hazards in weak water-rich faulted zone rocks, water inrush in karst passages, and micro-crack water inrush, respectively. Complement technologies and equipment for industrial applications were also proposed. Additionally, a novel full-life periodic dynamic water grouting with the critical grouting borehole as the core was proposed. The key techniques for the control of water inrush in water-rich faulted zone, jointed fissures and karst passages, and micro-crack water inrush were developed.展开更多
To study the penetration mechanism of cement-based slurry in intersected fractures during grouting and the related pressure distribution,we have used two different variants of cement,namely,basic cement slurry and fas...To study the penetration mechanism of cement-based slurry in intersected fractures during grouting and the related pressure distribution,we have used two different variants of cement,namely,basic cement slurry and fast-setting cement slurry.The influence of a retarder,time-varying viscosity,fracture width and location of injection hole is also considered.A finite element software is used to implement two and three-dimensional numerical models for grouting of intersected fractures in hydrostatic conditions.Results show that there are significant differences in the diffusion morphology and pressure distribution depending on the considered cement slurry.Retarder can effectively slow down the rising rate of injection pressure and extend the diffusion distance of grout.The influence of the branch fracture is more important when basic cement slurry is considered,indicating that the change of grout pressure is correlated with the slurry viscosity.The faster the viscosity increases,the less evident is the effect.展开更多
People are increasingly aware of the role of vegetarian diets in modulating human gut microbial abundance and intestinal physiology.A plant-based diet is thought to benefit host health by contributing to establish a d...People are increasingly aware of the role of vegetarian diets in modulating human gut microbial abundance and intestinal physiology.A plant-based diet is thought to benefit host health by contributing to establish a diverse and stable microbiome.In addition,microbe-derived metabolites of specific nutrients known to be abundant in vegetarian diets(such as indigestible carbohydrates,arginine,and others) are important to promote effective intestinal immune responses,maintain intestinal barrier function,and protect against pathogens.This review explores the characteristics of the gut microbiome formed by vegetarian diets and the effects of diet-associated nutrients on intestinal microbial abundance.The interactions between the microbe-derived metabolites of vegetarian diet-associated nutrients and intestinal physiology are also discussed.展开更多
A branched core-shell nanosphere composed of an anatase TiO_(2)(a-TiO_(2)) core and a TiO_(2)nanobranch shell with gradient-doped N(a-TiO_(2)@N-TiO_(2)) is synthesized by a simple in situ doping method, in which mixed...A branched core-shell nanosphere composed of an anatase TiO_(2)(a-TiO_(2)) core and a TiO_(2)nanobranch shell with gradient-doped N(a-TiO_(2)@N-TiO_(2)) is synthesized by a simple in situ doping method, in which mixed crystal anatase-rutile TiO_(2)(ar-TiO_(2)) nanosphere is first prepared by oxidizing Ti using H_(2)O_(2), and then is etched by NH_(3)·H_(2)O to form(NH_(4))2TiO_(3)nanobranches, which is converted into a-TiO_(2)@N-TiO_(2)following an ambient annealing process. The diameter of a-TiO_(2)core is ~500 nm, and the thickness of NTiO_(2)branched shell is ~100 nm with gradually increased N concentration from the bottom to the edge.Ultra-thin amorphous coating layers on the branches are also observed. The morphology of the composites could be further tuned by the amount of NH_(3)·H_(2)O, and its effect on the photocatalytic performance is also investigated. The optimized a-TiO_(2)@N-TiO_(2)shows an outstanding hydrogen evolution rate of 308.1 μmol g^(-1)h^(-1)under air mass(AM) 1.5 illumination, and also exhibits highly active in photocatalytic degradation of various refractory organic pollutants, including organic dyes, phenols, antibiotics,and personal care products, with removal ratios higher than 96% after 2 h operation. This can be due to the gradient-doped N-TiO_(2)nanobranches, which not only provide bending band structure and defect level derived from the N impurities and O vacancies, resulting the formation of n-n+heterojunctions to improve the charge separation, but also enhance the charge transfer at the liquid-solid interface due to the numerous nanobranches and amorphous coating layers.展开更多
Pre?grouting is a popular ground treatment strategy utilized to enhance the strength and stability of strata during the excavation of a tunnel through a fault zone.Two important questions need to be answered during su...Pre?grouting is a popular ground treatment strategy utilized to enhance the strength and stability of strata during the excavation of a tunnel through a fault zone.Two important questions need to be answered during such an excavation.First,how should the grouting size be determined?Second,when should excavation begin after grouting?These two questions are conventionally addressed through empirical experience and standard criteria because a reliable quantitative approach,which would be preferable,has not yet been developed.To address these questions,we apply a recently proposed numerical approach known as discontinuity layout optimization,an efficient node-based upper bound limit analysis method.A case study is provided utilizing a tunnel located in a stratum characterized by complicated geological conditions,including soft soil and a fault zone.The factor of safety is used to quantitatively assess the stability of the tunnel section.The influences of the grouted zone thickness and the time-dependent material properties of the grouted zone on the stability of the tunnel section are evaluated,thereby assisting designers by quantitatively assessing the effects of pre-grouting.展开更多
InChina,a new“epic project”named theSichuan-Tibet railway linkingChengdu and Lhasa is in the construction phase.This 1,592-km-long railway passes through the western Sichuan basin,subsequently climbing 5,000 m and r...InChina,a new“epic project”named theSichuan-Tibet railway linkingChengdu and Lhasa is in the construction phase.This 1,592-km-long railway passes through the western Sichuan basin,subsequently climbing 5,000 m and running across the“roof of the world”Tibet plateau,which is dubbed the“Sky-High Road”(Figure 1).展开更多
Auxetic metastructures have attracted tremendous attention because of their robust multifunctional properties and promising potential industrial applications.This paper studies the in-plane mechanical behaviors of a c...Auxetic metastructures have attracted tremendous attention because of their robust multifunctional properties and promising potential industrial applications.This paper studies the in-plane mechanical behaviors of a chiral S-shaped metastructure subjected to tensile loading in both X-direction and Y-direction and wave propagation properties using the finite element(FE)method.The relationships between structural parameters and elastic behaviors are also discussed.The results indicate that the orientation of chiral S-shaped metastructure under tensile loading in the X-direction exhibits higher auxeticity and stiffness.Then,the band structures and the edge modes of each band gap of the chiral S-shaped metastructure are explored,and the relations between band gap properties and structural parameters are also systematically analyzed.Moreover,we explore the wave mitigation of the chiral S-shaped metastructures by regulating the structural parameters.Finally,the transmission properties of the finite chiral S-shaped periodic metastructures are studied to confirm the results of band gap simulation.This study promotes the engineering application of vibration isolation of chiral structures based on the band gap theory.展开更多
The synthesis of new C–C bonded two-dimensional(2D)covalent organic frameworks(COFs)is highly desirable.Here,a simple but effective synthetic strategy has been developed using an irreversible Brønsted acid-catal...The synthesis of new C–C bonded two-dimensional(2D)covalent organic frameworks(COFs)is highly desirable.Here,a simple but effective synthetic strategy has been developed using an irreversible Brønsted acid-catalyzed aldol cyclotrimerization reaction by virtue of truxene as a linkage.Nonolefin C–C bonded 2D truxene-based covalent organic frameworks(Tru-COFs)were constructed by polymerization of 1,3,5-triindanonebenzene(TDB).The structure formation was confirmed by wide-angle X-ray scattering,Fourier-transform infrared spectroscopy,and solid-state^(13)C CP/MAS NMR.The results showed that the Tru-COFs were porous(645 m^(2)/g)and chemically stable.Benzyl methylene in conjugated Tru-COFs more effectively produced photoinduced radicals than the model truxene compound.Due to the radical photoresponsiveness,Tru-COFs were efficient catalysts for photocatalytic oxidation of sulfides.We expect that this will provide a new synthetic methodology to obtain C–C bonded functional 2D COFs.展开更多
The synthesis of new C–C bonded two-dimensional(2D)covalent organic frameworks(COFs)is highly desirable.Here,a simple but effective synthetic strategy has been developed using an irreversible Brønsted acid-catal...The synthesis of new C–C bonded two-dimensional(2D)covalent organic frameworks(COFs)is highly desirable.Here,a simple but effective synthetic strategy has been developed using an irreversible Brønsted acid-catalyzed aldol cyclotrimerization reaction by virtue of truxene as a linkage.Nonolefin C–C bonded 2D truxene-based covalent organic frameworks(Tru-COFs)were constructed by polymerization of 1,3,5-triindanonebenzene(TDB).The structure formation was confirmed by wide-angle X-ray scattering,Fourier-transform infrared spectroscopy,and solid-state ^(13)C CP/MAS NMR.The results showed that the Tru-COFs were porous(645 m^(2)/g)and chemically stable.Benzyl methylene in conjugated Tru-COFs more effectively produced photoinduced radicals than the model truxene compound.Due to the radical photoresponsiveness,Tru-COFs were efficient catalysts for photocatalytic oxidation of sulfides.We expect that this will provide a new synthetic methodology to obtain C–C bonded functional 2D COFs.展开更多
文摘Grouting is a major method used to prevent water and mud inrush in tunnels and underground engineering. In this paper, the current situation of control and prevention of water and mud inrush is summarized and recent advances in relevant theories, grout/equipment, and critical techniques are introduced. The time-variant equations of grout viscosity at different volumetric ratios were obtained based on the constitutive relation of typical fast curing grouts. A large-scale dynamic grouting model testing system （4000 mm × 2000 mm × 5 mm） was developed, and the diffusions of cement and fast curing grouts in dynamic water grouting were investigated. The results reveal that the diffusions of cement grouts and fast curing grouts are U-shaped and asymmetric elliptical, respectively. A multi-parameter real-time monitoring system （＆#981; = 1.5 m, h = 1.2 m） was developed for the grouting process to study the diffusion and reinforcement mechanism of grouting in water-rich faulted zone. A high early strength cream-type reinforcing/plugging grout, a high permeability nano-scale silica gel grout, and a high-expansion filling grout were proposed for the control of water hazards in weak water-rich faulted zone rocks, water inrush in karst passages, and micro-crack water inrush, respectively. Complement technologies and equipment for industrial applications were also proposed. Additionally, a novel full-life periodic dynamic water grouting with the critical grouting borehole as the core was proposed. The key techniques for the control of water inrush in water-rich faulted zone, jointed fissures and karst passages, and micro-crack water inrush were developed.
基金by the Joint Funds of National Natural Science Foundation of China[Grant No.U1706223]the National Key Research and Development Project(Grant No.2016YFC0801600)+1 种基金the General Program of National Natural Science Foundation[Grant No.51779133]the General Program of Shandong Province Natural Science Foundation[Grant No.ZR2018MEE047].
文摘To study the penetration mechanism of cement-based slurry in intersected fractures during grouting and the related pressure distribution,we have used two different variants of cement,namely,basic cement slurry and fast-setting cement slurry.The influence of a retarder,time-varying viscosity,fracture width and location of injection hole is also considered.A finite element software is used to implement two and three-dimensional numerical models for grouting of intersected fractures in hydrostatic conditions.Results show that there are significant differences in the diffusion morphology and pressure distribution depending on the considered cement slurry.Retarder can effectively slow down the rising rate of injection pressure and extend the diffusion distance of grout.The influence of the branch fracture is more important when basic cement slurry is considered,indicating that the change of grout pressure is correlated with the slurry viscosity.The faster the viscosity increases,the less evident is the effect.
基金supported by the National Natural Science Foundation of China Program [No. 31871773 and No. 31820103010]Projects of Innovation and Development Pillar Program for Key Industries in Southern Xinjiang of Xinjiang Production and Construction Corps [2018DB002]National First-Class Discipline Program of Food Science and Technology [JUFSTR20180102]。
文摘People are increasingly aware of the role of vegetarian diets in modulating human gut microbial abundance and intestinal physiology.A plant-based diet is thought to benefit host health by contributing to establish a diverse and stable microbiome.In addition,microbe-derived metabolites of specific nutrients known to be abundant in vegetarian diets(such as indigestible carbohydrates,arginine,and others) are important to promote effective intestinal immune responses,maintain intestinal barrier function,and protect against pathogens.This review explores the characteristics of the gut microbiome formed by vegetarian diets and the effects of diet-associated nutrients on intestinal microbial abundance.The interactions between the microbe-derived metabolites of vegetarian diet-associated nutrients and intestinal physiology are also discussed.
基金supported by the National Natural Science Foundation of China (No. 52170083)the Excellent Youth Fund Project of Natural Science Foundation of Hunan Province (No.2021JJ20007)the Research Foundation of Education Bureau of Hunan Province,China (No. 21B0441)。
文摘A branched core-shell nanosphere composed of an anatase TiO_(2)(a-TiO_(2)) core and a TiO_(2)nanobranch shell with gradient-doped N(a-TiO_(2)@N-TiO_(2)) is synthesized by a simple in situ doping method, in which mixed crystal anatase-rutile TiO_(2)(ar-TiO_(2)) nanosphere is first prepared by oxidizing Ti using H_(2)O_(2), and then is etched by NH_(3)·H_(2)O to form(NH_(4))2TiO_(3)nanobranches, which is converted into a-TiO_(2)@N-TiO_(2)following an ambient annealing process. The diameter of a-TiO_(2)core is ~500 nm, and the thickness of NTiO_(2)branched shell is ~100 nm with gradually increased N concentration from the bottom to the edge.Ultra-thin amorphous coating layers on the branches are also observed. The morphology of the composites could be further tuned by the amount of NH_(3)·H_(2)O, and its effect on the photocatalytic performance is also investigated. The optimized a-TiO_(2)@N-TiO_(2)shows an outstanding hydrogen evolution rate of 308.1 μmol g^(-1)h^(-1)under air mass(AM) 1.5 illumination, and also exhibits highly active in photocatalytic degradation of various refractory organic pollutants, including organic dyes, phenols, antibiotics,and personal care products, with removal ratios higher than 96% after 2 h operation. This can be due to the gradient-doped N-TiO_(2)nanobranches, which not only provide bending band structure and defect level derived from the N impurities and O vacancies, resulting the formation of n-n+heterojunctions to improve the charge separation, but also enhance the charge transfer at the liquid-solid interface due to the numerous nanobranches and amorphous coating layers.
基金financial support by the National Natural Science Foundation of China(Grant No.51809069)the Hebei Province Natural Science Fund(No.E2019202441).
文摘Pre?grouting is a popular ground treatment strategy utilized to enhance the strength and stability of strata during the excavation of a tunnel through a fault zone.Two important questions need to be answered during such an excavation.First,how should the grouting size be determined?Second,when should excavation begin after grouting?These two questions are conventionally addressed through empirical experience and standard criteria because a reliable quantitative approach,which would be preferable,has not yet been developed.To address these questions,we apply a recently proposed numerical approach known as discontinuity layout optimization,an efficient node-based upper bound limit analysis method.A case study is provided utilizing a tunnel located in a stratum characterized by complicated geological conditions,including soft soil and a fault zone.The factor of safety is used to quantitatively assess the stability of the tunnel section.The influences of the grouted zone thickness and the time-dependent material properties of the grouted zone on the stability of the tunnel section are evaluated,thereby assisting designers by quantitatively assessing the effects of pre-grouting.
基金supported by the National Basic Research Program of China(2016YFA0200101)the National Natural Science Foundation of China(21633012 and 61890940)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)(XDB30000000)he CAS Key Research Program of Frontier Sciences(QYZDY-SSWSLH029)。
文摘InChina,a new“epic project”named theSichuan-Tibet railway linkingChengdu and Lhasa is in the construction phase.This 1,592-km-long railway passes through the western Sichuan basin,subsequently climbing 5,000 m and running across the“roof of the world”Tibet plateau,which is dubbed the“Sky-High Road”(Figure 1).
基金supported by the National Natural Science Foundation of China under the Grant Number of 12072241 and the Fundamental Research Funds for the Central Universities under the Grant Number of 2042022kf0009.
文摘Auxetic metastructures have attracted tremendous attention because of their robust multifunctional properties and promising potential industrial applications.This paper studies the in-plane mechanical behaviors of a chiral S-shaped metastructure subjected to tensile loading in both X-direction and Y-direction and wave propagation properties using the finite element(FE)method.The relationships between structural parameters and elastic behaviors are also discussed.The results indicate that the orientation of chiral S-shaped metastructure under tensile loading in the X-direction exhibits higher auxeticity and stiffness.Then,the band structures and the edge modes of each band gap of the chiral S-shaped metastructure are explored,and the relations between band gap properties and structural parameters are also systematically analyzed.Moreover,we explore the wave mitigation of the chiral S-shaped metastructures by regulating the structural parameters.Finally,the transmission properties of the finite chiral S-shaped periodic metastructures are studied to confirm the results of band gap simulation.This study promotes the engineering application of vibration isolation of chiral structures based on the band gap theory.
基金support from the Research Program of the Chinese Academy of Sciences(No.XDB30000000)the National Natural Science Foundation of China(Nos.21633012,61890940,and 21922511)+1 种基金the National Basic Research Program of China the Strategic Priority(2016YFA0200101 and 2018YFA0703200)the CAS Key Research Program of Frontier Sciences(QYZDY-SSWSLH029).
文摘The synthesis of new C–C bonded two-dimensional(2D)covalent organic frameworks(COFs)is highly desirable.Here,a simple but effective synthetic strategy has been developed using an irreversible Brønsted acid-catalyzed aldol cyclotrimerization reaction by virtue of truxene as a linkage.Nonolefin C–C bonded 2D truxene-based covalent organic frameworks(Tru-COFs)were constructed by polymerization of 1,3,5-triindanonebenzene(TDB).The structure formation was confirmed by wide-angle X-ray scattering,Fourier-transform infrared spectroscopy,and solid-state^(13)C CP/MAS NMR.The results showed that the Tru-COFs were porous(645 m^(2)/g)and chemically stable.Benzyl methylene in conjugated Tru-COFs more effectively produced photoinduced radicals than the model truxene compound.Due to the radical photoresponsiveness,Tru-COFs were efficient catalysts for photocatalytic oxidation of sulfides.We expect that this will provide a new synthetic methodology to obtain C–C bonded functional 2D COFs.
基金support from the Research Program of the Chinese Academy of Sciences(No.XDB30000000)the National Natural Science Foundation of China(Nos.21633012,61890940,and 21922511)+1 种基金the National Basic Research Program of China the Strategic Priority(2016YFA0200101 and 2018YFA0703200)the CAS Key Research Program of Frontier Sciences(QYZDY-SSWSLH029).
文摘The synthesis of new C–C bonded two-dimensional(2D)covalent organic frameworks(COFs)is highly desirable.Here,a simple but effective synthetic strategy has been developed using an irreversible Brønsted acid-catalyzed aldol cyclotrimerization reaction by virtue of truxene as a linkage.Nonolefin C–C bonded 2D truxene-based covalent organic frameworks(Tru-COFs)were constructed by polymerization of 1,3,5-triindanonebenzene(TDB).The structure formation was confirmed by wide-angle X-ray scattering,Fourier-transform infrared spectroscopy,and solid-state ^(13)C CP/MAS NMR.The results showed that the Tru-COFs were porous(645 m^(2)/g)and chemically stable.Benzyl methylene in conjugated Tru-COFs more effectively produced photoinduced radicals than the model truxene compound.Due to the radical photoresponsiveness,Tru-COFs were efficient catalysts for photocatalytic oxidation of sulfides.We expect that this will provide a new synthetic methodology to obtain C–C bonded functional 2D COFs.
