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Impacts of the unsaturation degree of long-chain fatty acids on the volatile fatty acid profiles of rumen microbial fermentation in goats in vitro 被引量:4
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作者 GAO Jian WANG Meng-zhi +3 位作者 JING Yu-jia SUN Xue-zhao WU Tian-yi SHI Liang-feng 《Journal of Integrative Agriculture》 SCIE CAS CSCD 2016年第12期2827-2833,共7页
This study investigated the impacts of the degree of unsaturation (unsaturity) of long-chain fatty acids on volatile fatty acid (VFA) profiles of rumen fermentation in vitro. Six types of long-chain fatty acids, i... This study investigated the impacts of the degree of unsaturation (unsaturity) of long-chain fatty acids on volatile fatty acid (VFA) profiles of rumen fermentation in vitro. Six types of long-chain fatty acids, including stearic acid (C18:0, control group), oleic acid (C18:1, n-9), linoleic acid (C18:2, n-6), a-linolenic acid (C18:3, n-3), arachidonic acid (C20:4, n-6) and eicosapentaenoic acid (C20:5, n-3), were tested. Rumen fluid from three goats fitted with ruminal fistulae was used as inoculum and the inclusion rate of long-chain fatty acid was at 3% (w/w) of substrate. Samples were taken for VFA analysis at 0, 3, 6, 9, 12, 18 and 24 h of incubation, respectively. The analysis showed that there were significant differences in the total VFA among treatments, sampling time points, and treatment×time point interactions (P〈0.01). a-Linolenic acid had the highest total VFA (P〈0.01) among different long-chain fatty acids tested. The molar proportion of acetate in total VFA significantly differed among treatments (P〈0.01) and sampling time points (P〈0.01), but not treatment×time point interactions (P〉0.05). In contrast, the molar proportion of propionate did not differ among treatments during the whole incubation (P〉0.05). However, for butyrate molar proportions, significant differences were found not only among sampling time points but also among treatments and treatment×time point interactions (P〈0.01), with eicosapentaenoic acid having the highest value (P〈0.01). Additionally, no statistically significant differences were found in the acetate to propionate ratios among treatments groups (P〉0.05), even the treatments stearic acid and a-linolenic acid were numerically higher than the others. The inclusion of 3% long-chain unsaturated fatty acids differing in the degree of unsaturation brought out a significant quadratic regression relation between the total VFA concentration and the double bond number of fatty acid. In conclusion, the a-linolenic acid with 3 double bonds appeared better for improving rumen microbial fermentation and the total VFA concentration. 展开更多
关键词 volatile fatty acid unsaturation degree long-chain fatty acid in vitro fermentation
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Unsaturation index and type 2 diabetes:Unknown,unloved 被引量:1
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作者 Rob NM Weijers 《World Journal of Meta-Analysis》 2015年第2期89-92,共4页
A useful parameter for interpreting analyses of membrane fatty-acid composition is the unsaturation index(UI),a measure of unsaturation that is calculated as the mean number of cis double bonds per fatty-acid residue ... A useful parameter for interpreting analyses of membrane fatty-acid composition is the unsaturation index(UI),a measure of unsaturation that is calculated as the mean number of cis double bonds per fatty-acid residue multiplied by 100.The UI is a fundamental parameter that contains information about many membrane biophysical properties and behavior.UI is a crucial index for type 2 diabetes(T2D) and other disorders,yet it is not properly considered in the scientific community.The goal of the present editorial is to familiarize the scientific T2 D community with the UI.The idea of early systemic cell-membrane disease necessitates new thinking andsuggests that UI should feature prominently on the research agenda. 展开更多
关键词 Type 2 diabetes unsaturation index PHOSPHOLIPID Cell membrane Fatty acid
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Effects of Cadmium on Polar Lipid Composition and Unsaturation in Maize(Zea mays) in Hydroponic Culture 被引量:2
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作者 Radhouane Chaffai Tinni Nouhou Seybou +1 位作者 Brahim Marzouk Ezzedine EI Ferjani 《Journal of Integrative Plant Biology》 SCIE CAS CSCD 2007年第12期1693-1702,共10页
This study aimed to evaluate the effect of Cd exposure (100 μmol/L) on polar lipid composition, and to examine the level of fatty acid unsaturation in maize (Zea mays L.). In roots, the level of 16:0 and monouns... This study aimed to evaluate the effect of Cd exposure (100 μmol/L) on polar lipid composition, and to examine the level of fatty acid unsaturation in maize (Zea mays L.). In roots, the level of 16:0 and monounsaturated fatty acids (16:1 + 18:1) decreased in phosphatidylcholine (PC) and phosphatidylethanolamine (PE). In contrast, the proportion of unsaturated 18-C fatty acid species showed an opposite response to Cd. The content, on the other hand, of PC, PE, digalactosyldiacylglycerol (DGDG), and steryl lipids increased in roots (2.9-, 1.6-, 5.3-, and 1.7-fold increase, respectively). These results suggest that a more unsaturated fatty acid composition than found in control plants with a concomitant increase in polar lipids may favor seedling growth during Cd exposure. However, the observed increase in the steryl lipid (SL) : phospholipid (PL) ratio (twofold), the decrease in monogalactosyldiacylglycerol (MGDG) : DGDG ratio, as well as the induction of lipid peroxidation in roots may represent symptoms of membrane injury. In shoots, the unsaturation level was markedly decreased in PC and phosphatidylglycerol (PG) after Cd exposure, but showed a significant increase in sulfoquinovosyldiacylglycerol (SQDG), MGDG and DGDG. The content of PG and MGDG was decreased by about 65%, while PC accumulated to higher levels (4.4-fold increase). Taken together, these changes in the polar lipid unsaturation and composition are likely to be due to alterations in the glycerolipid pathway. These results also support the idea that the increase in overall unsaturation plays some role in enabling the plant to withstand the metal exposure. 展开更多
关键词 CADMIUM fatty acids heavy metal stress lipid peroxidation polar lipids unsaturation level Zea mays.
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Effects of fatty acid chain length and degree of unsaturation on the surface activities of monoacyl trehaloses
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作者 Yue-E SUN Wenshui XIA +2 位作者 Xueyan TANG Zhiyong HE Jie CHEN 《Frontiers of Chemical Science and Engineering》 SCIE EI CSCD 2009年第4期407-412,共6页
The surface properties of monoacyl trehaloses with different acyl chains were investigated at 30℃,40℃,50℃,and 60℃.Monoacyl trehaloses were enzymatically synthesized and purified with silica gel column chromatograp... The surface properties of monoacyl trehaloses with different acyl chains were investigated at 30℃,40℃,50℃,and 60℃.Monoacyl trehaloses were enzymatically synthesized and purified with silica gel column chromatography and semi-preparative high-performance liquid chromatography(HPLC),and the purity of products was identified by mass spectrometry(MS)and nuclear magnetic resonance(NMR).The surface tension of monoacyl trehalose in pure water was measured using Doüy ring method at different temperatures.The critical micelle concentrations(CMC),surface tension at the CMC,γCMC,and residual area per molecule,a,were estimated from the curves.The CMC value of unsaturated monoacyl trehalose was affected by both the degree of unsaturation and the acyl chain length,and the effect of chain length on the CMC value was much stronger than that of the unsaturation degree.However,there was no significant dependency of theγCMC value and a values on the chain length or the unsaturated degree. 展开更多
关键词 monoacyl trehalose surface properties degree of unsaturation critical micelle concentration
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Lysophosphatidic acid signaling:Transmembrane modulators in the central nervous system
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作者 Alexandra Polyzou Alexandros Κ.Tsiouris +2 位作者 Charalampos Labrakakis Britta J.Eickholt George Leondaritis 《Neural Regeneration Research》 2026年第3期1104-1105,共2页
Lysophosphatidic acid(LPA)is a pleiotropic lipid agonist essential for functions of the central nervous system(CNS).It is abundant in the developing and adult brain while its concentration in biological fluids,includi... Lysophosphatidic acid(LPA)is a pleiotropic lipid agonist essential for functions of the central nervous system(CNS).It is abundant in the developing and adult brain while its concentration in biological fluids,including cerebrospinal fluid,varies significantly(Figure 1Α;Yung et al.,2014).LPA actually corresponds to a variety of lipid species that include different stereoisomers with either saturated or unsaturated fatty acids bearing likely differentiated biological activities(Figure 1Α;Yung et al.,2014;Hernández-Araiza et al.,2018). 展开更多
关键词 transmembrane modulators cerebrospinal fluidvaries variety lipid species lysophosphatidic acid biological fluidsincluding lysophosphatidic acid lpa saturated unsaturated fatty acids pleiotropic lipid agonist
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Three-dimensional stability of two-step slope with crack considering temperature effect on unsaturated soil
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作者 SHAN Jun-tao WU Yi-min YANG Xiao-li 《Journal of Central South University》 2025年第3期1060-1079,共20页
In existing studies, most slope stability analyses concentrate on conditions with constant temperature, assuming the slope is intact, and employ the Mohr-Coulomb (M-C) failure criterion for saturated soil to character... In existing studies, most slope stability analyses concentrate on conditions with constant temperature, assuming the slope is intact, and employ the Mohr-Coulomb (M-C) failure criterion for saturated soil to characterize the strength of the backfill. However, the actual working temperature of slopes varies, and natural phenomena such as rainfall and groundwater infiltration commonly result in unsaturated soil conditions, with cracks typically present in cohesive slopes. This study introduces a novel approach for assessing the stability of unsaturated soil stepped slopes under varying temperatures, incorporating the effects of open and vertical cracks. Utilizing the kinematic approach and gravity increase method, we developed a three-dimensional (3D) rotational wedge failure mechanism to simulate slope collapse, enhancing the traditional two-dimensional analyses. We integrated temperature-dependent functions and nonlinear shear strength equations to evaluate the impact of temperature on four typical unsaturated soil types. A particle swarm optimization algorithm was employed to calculate the safety factor, ensuring our method’s accuracy by comparing it with existing studies. The results indicate that considering 3D effects yields a higher safety factor, while cracks reduce slope stability. Each unsaturated soil exhibits a distinctive temperature response curve, highlighting the importance of understanding soil types in the design phase. 展开更多
关键词 3D two-step slope cracks temperature effects unsaturation limit analysis
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Influences of strain rate on mechanical behaviors of unsaturated and quasi-saturated loess under varying drainage conditions 被引量:1
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作者 Tongwei Zhang Sheng Li +2 位作者 Hengxing Lan Huyuan Zhang Fanyu Zhang 《Journal of Rock Mechanics and Geotechnical Engineering》 2025年第2期1163-1181,共19页
Although time-dependent deformation of geomaterials underpins slope-failure prediction models,the influence of strain rate on shearing strength and deformation behavior of loess remains unclear.The consolidated undrai... Although time-dependent deformation of geomaterials underpins slope-failure prediction models,the influence of strain rate on shearing strength and deformation behavior of loess remains unclear.The consolidated undrained(CU)and drained(CD)triaxial testing elucidated the impact of strain rate(0.005–0.3 mm/min)on strength envelopes,deformation moduli,pore pressures,and dilatancy characteristics of unsaturated and quasi-saturated loess.Under drained conditions with a controlled matric suction of 50 kPa,increasing strain rates from 0.005 mm/min to 0.011 mm/min induced decreases in failure deviatoric stress(qf),initial deformation modulus(Ei),and cohesion(c),while friction angles remained unaffected.Specimens displayed initial contractive volumetric strains transitioning to dilation across varying confining pressures.Higher rates diminished contractive volumetric strains and drainage volumes,indicating reduced densification and strength in the shear zone.Under undrained conditions,both unsaturated and quasi-saturated(pore pressure coefficient B=0.75)loess exhibited deteriorating mechanical properties with increasing rates from 0.03 mm/min to 0.3 mm/min.For unsaturated loess,reduced contractive volumetric strains at higher rates manifested relatively looser structures in the pre-peak stress phase.The strength decrement in quasi-saturated loess arose from elevated excess porewater pressures diminishing effective stresses.Negative porewater pressures emerged in quasi-saturated loess at lower confining pressures and strain rates.Compared to previous studies,the qf and Ei exhibited rate sensitivity below threshold values before attaining minima with marginal subsequent influence.The underlying mechanism mirrors the transition from creep to accelerated deformation phase of landslides. 展开更多
关键词 Unsaturated loess Strain rate Shearing strength Deformation modulus Drainage conditions
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An effective stress-based DSC model for predicting hydromechanical shear behavior of unsaturated collapsible soils subjected to initial shear stress 被引量:1
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作者 Saman Soleymani Borujerdi S.Mohsen Haeri +1 位作者 Amir Akbari Garakani Chandrakant SDesai 《Journal of Rock Mechanics and Geotechnical Engineering》 2025年第1期539-555,共17页
Evaluation of hydromechanical shear behavior of unsaturated soils is still a challenging issue. The time and cost needed for conducting precise experimental investigation on shear behavior of unsaturated soils have en... Evaluation of hydromechanical shear behavior of unsaturated soils is still a challenging issue. The time and cost needed for conducting precise experimental investigation on shear behavior of unsaturated soils have encouraged several investigators to develop analytical, empirical, or semi-empirical models for predicting the shear behavior of unsaturated soils. However, most of the previously proposed models are for specimens subjected to the isotropic state of stress, without considering the effect of initial shear stress. In this study, a hydromechanical constitutive model is proposed for unsaturated collapsible soils during shearing, with consideration of the effect of the initial shear stress. The model implements an effective stress-based disturbed state concept (DSC) to predict the stress-strain behavior of the soil. Accordingly, material/state variables were defined for both the start of the shearing stage and the critical state of the soil. A series of laboratory tests was performed using a fully automated unsaturated triaxial device to verify the proposed model. The experimental program included 23 suction-controlled unsaturated triaxial shear tests on reconstituted specimens of Gorgan clayey loess wetted to different levels of suctions under both isotropic and anisotropic stress states. The results show excellent agreement between the prediction by the proposed model and the experimental results. 展开更多
关键词 Unsaturated collapsible soil Initial shear stress Hydromechanical shear behavior Effective stress Disturbed state concept Critical state
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Induction of hyperlipidemic pancreatitis by different fatty acids:A narrative review 被引量:1
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作者 Yu-Xi Wang Peng Ge Hai-Long Chen 《World Journal of Gastroenterology》 2025年第22期1-15,共15页
Epidemiological evidence suggests that there is a direct relationship between the degree of obesity and acute pancreatitis severity.Intake of different fatty acids leads to different types of hyperlipidemias.Adipose d... Epidemiological evidence suggests that there is a direct relationship between the degree of obesity and acute pancreatitis severity.Intake of different fatty acids leads to different types of hyperlipidemias.Adipose degradation by pancreatic lipase generates different free fatty acids,which can exacerbate pancreatitis.Saturated fatty acids(SFAs)play an inflammatory role in human metabolic syndrome and obesity,whereas unsaturated fatty acids(UFAs)are“good fats”that are thought to enhance overall health status.However,it appears that serum UFAs correlate with severe acute pancreatitis.Additionally,the“obesity paradox”suggests that UFAs potentially minimize direct harm to the organ.This review provides an in-depth overview of the role of SFAs and UFAs in acute pancreatitis of hyperlipidemia and discusses potential prevention targets for severe acute pancreatitis. 展开更多
关键词 Severe acute pancreatitis HYPERTRIGLYCERIDEMIA Saturated fatty acid Unsaturated fatty acid M1 macrophage polarization
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Application of Functional Group Migration Strategies in Photodriven Difunctionalization of Unsaturated Hydrocarbons
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作者 He Chonglong Zhou Youkang +1 位作者 Duan Xinhua Liu Le 《有机化学》 北大核心 2025年第5期1478-1508,共31页
Difunctionalization of unsaturated hydrocarbons is a pivotal synthetic strategy enabling the conversion of alkenes and alkynes into high value-added compounds.It allows for the introduction of two functional groups in... Difunctionalization of unsaturated hydrocarbons is a pivotal synthetic strategy enabling the conversion of alkenes and alkynes into high value-added compounds.It allows for the introduction of two functional groups into the unsaturated bond in a single step,facilitating the efficient construction of complex molecular architectures,which has been widely utilized in material chemistry,pharmaceutical and fine chemical synthesis.Recently,significant progress has been made via free radical-mediated difunctionalization due to the extensive application of photocatalysis.However,highly selective difunc-tionalization reactions still remain challenging.The research progress of selective difunctionalization of unsaturated hydro-carbons using a free radical addition/functional group migration strategy over the past decade is summarized,and synthetic strategies and key reaction steps are systematically elaborated. 展开更多
关键词 visible-light-driven unsaturated hydrocarbon functional group migration difunctionalization
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Unsaturated cobalt single-atoms stabilized by silanol nests of zeolites for efficient propane dehydrogenation
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作者 Liwen Guo Dao Shi +4 位作者 Tianjun Zhang Yanhang Ma Guodong Qi Jun Xu Qiming Sun 《Chinese Journal of Catalysis》 2025年第5期323-333,共11页
Propane dehydrogenation(PDH)has emerged as a key on-purpose technology for the production of propylene,but it often depends on toxic chromium and expensive platinum catalysts,highlighting the need for environmentally ... Propane dehydrogenation(PDH)has emerged as a key on-purpose technology for the production of propylene,but it often depends on toxic chromium and expensive platinum catalysts,highlighting the need for environmentally friendly and cost-effective alternatives.In this study,we developed a facile impregnation method to fabricate unsaturated Co single-atoms with a tricoordinated Co_(1)O_(3)H_(x) structure by regulating silanol nests in purely siliceous Beta zeolites.Detailed PDH catalytic tests and characterizations revealed a positive correlation between the presence of silanol nests and enhanced catalytic activity.Additionally,the unsaturated Co single-atoms exhibited a carbon deposition rate more than an order of magnitude slower than that of Co nanoparticles.Notably,the optimized Co_(0.3%)/deAl-meso-Beta catalyst achieved a record-high propylene formation rate of 21.2 mmol_(C3H6) g_(cat)^(-1) h^(-1),with an exceptional propylene selectivity of 99.1%at 550℃.Moreover,the Co_(0.3%)/deAl-meso-Beta catalyst demonstrated excellent stability,with negligible deactivation after 5 consecutive regeneration cycles.This study emphasizes the pivotal role of silanol nests of zeolites in stabilizing and modulating the coordination environment of metallic active sites,providing valuable insights for the design of high-activity,high-stability,and low-cost PDH catalysts. 展开更多
关键词 Propane dehydrogenation Unsaturated cobalt Single-atoms Silanol nest Zeolite
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Room-temperature olefin epoxidation reaction by two 2D cobalt metal-organic complexes under O_(2)atmosphere:Coordination and structural regulation
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作者 Yu-Yao Li Xiao-Hui Li +2 位作者 Zhi-Xuan An Yang Chu Xiu-Li Wang 《Chinese Chemical Letters》 2025年第4期490-495,共6页
Selective oxidation of olefin to epoxides is an important reaction in industry,however,developing heterogeneous catalysts to achieve the effective catalysis for this reaction under O_(2)atmosphere at room temperature ... Selective oxidation of olefin to epoxides is an important reaction in industry,however,developing heterogeneous catalysts to achieve the effective catalysis for this reaction under O_(2)atmosphere at room temperature is challenging but highly desired.In this work,two novel 2D cobalt metal-organic complexes,namely[Co(L)(5-HIP)]·2H_(2)O(Co-MOC-1)and[Co(L)(BTEC)_(0.5)]·H_(2)O(Co-MOC-2)(L=(E)-4,4-(ethene-1,2-diyl))bis(N-(pyridin-3-yl)benzamide;5-H_(2)HIP=5-hydroxyisophthalic acid;H4BTEC=pyromellitic acid)were designed and synthesized through hydrothermal method,which exhibited different metal coordination modes(4-coordinate and 5-coordinate,respectively)and 2D layer structures directed by different carboxylates co-ligands.Two Co-MOCs can serve as heterogeneous catalysts for the selective oxidation of olefins to epoxides at room temperature using O_(2)as oxidant.Furthermore,a higher catalysis activity of Co-MOC-1 than Co-MOC-2(96.7%vs.90.2%yield of 1,2-epoxycyclooctane)was observed,which may be attributed to the coordination unsaturated Co centers,the less coordination number and larger interlayer spacing of Co-MOC-1. 展开更多
关键词 EPOXIDATION Room-temperature reaction Metal-organic complex Heterogeneous catalysts Coordination unsaturated Co
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Investigation of magnesium phosphate cement on river dredged sludge with varying humic acid content and solidification mechanism
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作者 Xiaoyi Yuan Lei Peng Bing Chen 《Journal of Rock Mechanics and Geotechnical Engineering》 2025年第1期573-585,共13页
This paper investigated the use of magnesium phosphate cement (MPC) for solidifying sludge with different humic acid (HA) content (ranging from 0 to 4.5%) and explored the solidification mechanism. Fluidity, setting t... This paper investigated the use of magnesium phosphate cement (MPC) for solidifying sludge with different humic acid (HA) content (ranging from 0 to 4.5%) and explored the solidification mechanism. Fluidity, setting time, unconfined compressive strength (UCS), the strength formation mechanism, and the spontaneous imbibition process of solidified sludge (SS) were studied. The results indicate that MPC can be used as a low-alkalinity curing agent. As the HA content increases, fluidity and setting time also increase, while hydration temperature and strength decrease. Additionally, the failure mode of SS transitions from brittleness to ductility. The strength of SS is composed of the cementation strength provided by MPC hydration products, matric suction, osmotic suction, and the structural strength of the sludge. MPC reduces the structural strength caused by the shrinkage of pure sludge under the action of matric suction, but the incorporation of MPC significantly improved the strength when the sludge is eroded by water. X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that the sludge and MPC can form a dense solid body, forming various hydration products, and synergistically improve the mechanical properties of the sludge. 展开更多
关键词 Sludge solidification MPC Unsaturated spontaneous imbibition Strength mechanism Humic acid
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Hydrochar effects on the microstructure and hydromechanical behaviour of unsaturated compacted soils
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作者 Huan Dong Anthony Kwan Leung +2 位作者 Jianbin Liu Ali Akbar Karimzadeh Rui Chen 《Journal of Rock Mechanics and Geotechnical Engineering》 2025年第9期6045-6053,共9页
The effectiveness of using vegetation to stabilise shallow soil slopes heavily depends on the survival of vegetation,yet the amplification of extreme events induced by climate change threatens the health of plants cov... The effectiveness of using vegetation to stabilise shallow soil slopes heavily depends on the survival of vegetation,yet the amplification of extreme events induced by climate change threatens the health of plants covering slopes.Hydrochar is an environmentally friendly soil amender that can achieve the potential benefits of promoting plant growth for slope stabilisation and facilitation of waste upcycling.The mechanism underlying the hydrochar effects on the mechanical behaviour of unsaturated soils remains unclear.This study investigated the influence of grass-derived hydrochar on the water retention,compressibility,and shear strength of a compacted siltyeclay sand.Soil microstructural changes due to hydrochar amendment were measured to explain the soilehydrochar hydromechanical interaction.The increase in suction resulted in a less significant increase in yield stress and a negligible reduction in compressibility of the hydrochar-amended soil compared with the unamended case.This phenomenon was observed because hydrochar addition reduced the large pores with diameters greater than the macropore peak of 60 mm due to pore filling by hydrochar particles,resulting in a less substantial volume contraction during drying.Hydrochar introduced more significant effects on the soil’s shear strength in an unsaturated state compared to a saturated case.Despite the similarity of the unsaturated amended soil with the critical-state friction angle to the saturated case,the former exhibited a greater shear strength because the hydrochar addition improved water retention capability.As a result,the degree of saturation and,hence,Bishop’s effective stress were higher than those for the unamended case for a given suction. 展开更多
关键词 Hydrochar Saturated soils Unsaturated soils Mechanical behaviour Triaxial tests Critical state
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Passive earth pressure of narrow backfill considering seismic-unsaturated seepage multi-field coupling effect
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作者 WANG Ze-yue LIN Hang 《Journal of Central South University》 2025年第4期1447-1467,共21页
Narrow backfill earth pressure estimation is applied to study the stability of supporting structures in the vicinity of existing buildings.Previous narrow backfill earth pressure studies have neglected seismic-unsatur... Narrow backfill earth pressure estimation is applied to study the stability of supporting structures in the vicinity of existing buildings.Previous narrow backfill earth pressure studies have neglected seismic-unsaturated seepage multi-field coupling,resulting in inaccurate estimates.To address these deficiencies,this paper proposed a calculation method for seismic passive earth pressure in unsaturated narrow backfill,based on inclined thin-layer units.It considers the interlayer shear stress,arching effect,and the multi-field coupling of seismic-unsaturated seepage.Additionally,this paper includes a parametric sensitivity analysis.The outcomes indicate that the earthquake passive ground pressure of unsaturated narrow backfill can be reduced by increasing the aspect ratio,seismic acceleration coefficient,and unsaturation parameterα.It can also be reduced by decreasing the effective interior friction angle,soil cohesion,wallearth friction angle,and vertical discharge.Furthermore,for any width soil,lowering the elevation of the action point of passive thrust can be attained by raising the effective interior friction angle,wall-earth friction angle,and unsaturation parameterα.Reducing soil cohesion,seismic acceleration coefficient,and vertical discharge can also lower the height of the application point of passive thrust. 展开更多
关键词 passive earth pressure unsaturated steady seepage arching effect narrow backfill EARTHQUAKE
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Strength and dilatancy of an unsaturated expansive soil at high suction levels
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作者 Ke Chen Xuzhen He +1 位作者 Fayun Liang Daichao Sheng 《Journal of Rock Mechanics and Geotechnical Engineering》 2025年第8期5079-5088,共10页
A series of suction-controlled triaxial tests was conducted on Nanyang expansive clay to investigate the effects of dry density and suction on dilatancy and strength.The suction of the soil samples was controlled usin... A series of suction-controlled triaxial tests was conducted on Nanyang expansive clay to investigate the effects of dry density and suction on dilatancy and strength.The suction of the soil samples was controlled using a vapour equilibrium technique,with four suction levels ranging from 3.29 MPa to 198.14 MPa,where water retention is dominated by adsorption.The experimental results show that the tested soil exhibits a brittle failure mode under high suction,significantly distinguishing the hydro-mechanical behaviour of the soil at high suction from that observed at low suction.This brittle failure mode significantly increases the contribution of suction to peak strength compared to residual strength,causes the soil to fail before reaching the critical state,a phenomenon not observed in soils under high suction,and results in dilatancy caused by damage to the soil particle aggregates rather than particle rearrangement.The dilatancy data obtained from the triaxial tests reveal that significant soil dilatancy occurs during shear after reaching peak strength,with the maximum dilatancy angle increasing with suction and decreasing with confining pressure.However,the initial dry density has a negligible impact on the soil's dilatancy under high suction levels.This observation further supports that,for unsaturated soils under high suction levels,dilatancy is attributed to damage to soil particle aggregates rather than the rearrangement of soil particles. 展开更多
关键词 DILATANCY Critical state Shear strength Unsaturated soil
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Thermal mass transfer law and deformation properties of unsaturated sulfate saline soil
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作者 LIU Zhiyi SONG Yu +2 位作者 ZHOU Fengxi SUN Liepu GAO Fei 《Journal of Mountain Science》 2025年第6期2241-2260,共20页
The engineering diseases caused by seasonal sulfate saline soil in Hexi region of Gansu Province seriously affect the local infrastructure construction and operation maintenance.To address this issue,this study explor... The engineering diseases caused by seasonal sulfate saline soil in Hexi region of Gansu Province seriously affect the local infrastructure construction and operation maintenance.To address this issue,this study explored the thermal mass transfer law,pore fluid phase transition,soil deformation and microstructure of unsaturated sulfate saline soil under the open system.Firstly,based on the theories of porous media mechanics and continuum mechanics,combined with the conservation equations of mass,energy and momentum and considering the phase transition of pore fluid,a multi-field coupled mathematical model of hydro-thermal-salt-gasmechanical for unsaturated sulfate saline soil was established.Secondly,basic unknown variables such as pore water pressure,concentration,temperature,porosity,and displacement were selected to perform numerical simulation analysis on the equation system by“Comsol Multiphysics”finite element method.Finally,a comparative analysis was conducted between the on-site measured data and the numerical simulation results.The results show that the water and salt phase transitions caused by temperature change could lead to soil salt heave and frost heave,alter the pore structure of the soil,and reduce the compactness of the soil,ultimately being reflected in the changes in soil porosity.The influence of external temperature on soil temperature gradually decreases with increasing depth,and the sensitivity of frozen areas to external temperature is much higher than that of unfrozen areas.This study not only enriches the theoretical results of thermal mass transfer law and deformation of unsaturated sulfate saline soil,but also provides practical guidance for the prevention and control of engineering diseases in local sulfate saline soil. 展开更多
关键词 Unsaturated sulfate saline soil Thermal mass transfer Deformation properties Microstructure SATURATION
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Loading effects of unsaturated loess considering the influence of closed gas phase
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作者 Biao Qin Xi'an Li +2 位作者 Li Wang Hao Chai Qian Liu 《Journal of Rock Mechanics and Geotechnical Engineering》 2025年第4期2416-2432,共17页
Loess is susceptible to loading effects such as significant changes in strength and volume variation caused by loading and wetting.In this study,considering the different connection states of pore water and gas in loe... Loess is susceptible to loading effects such as significant changes in strength and volume variation caused by loading and wetting.In this study,considering the different connection states of pore water and gas in loess fabric,the gas phase closure case is incorporated into a unified form of the generalized effective stress framework,introducing a damage parameter considering the effects of closed pore gas.The loading effects of unsaturated loess under wide variations in saturation are described in a unified way,and the model performance is verified by corresponding stress and hydraulic path tests.The results indicated that the collapse response involves the initial void ratio of loess,and the coupled outwards motion of the loading-collapse(LC)yield surface under loading enhances its structural strength.Suction-enhanced yield stress requires a greater"tensile stress"to counteract its structural stability.The nucleation of bubbles at high saturation causes a decrease in yield stress.The loading effect exhibits a smaller collapse behavior when the influence of closed gas is considered,whereas the suction path does not cross the LC in the stress space under hydraulic action for the same parameters,which amplifies the influence of closed gas on loess deformation. 展开更多
关键词 Unsaturated loess Closed gas Generalized effective stress Loading effect Constitutive model
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Evaluating densification effect of ideal compaction grouting in unsaturated soils by volumetric water content
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作者 Qiong Wang Guang Hu +2 位作者 Shanyong Wang Wei Su Weimin Ye 《Journal of Rock Mechanics and Geotechnical Engineering》 2025年第8期5089-5098,共10页
Compaction grouting is primarily applied based on empiricism,and it is challenging to quantify its densification effect.To address this issue,five sets of laboratory model tests on ideal compaction grouting were condu... Compaction grouting is primarily applied based on empiricism,and it is challenging to quantify its densification effect.To address this issue,five sets of laboratory model tests on ideal compaction grouting were conducted,with varying pressures from 400 kPa to 800 kPa,to quantitatively evaluate the densification effect in unsaturated soils.The response of surrounding soil during compaction grouting was monitored.The changes in dry density and void ratio induced by compaction grouting were obtained by monitoring volumetric water content to determine compaction efficiency.In addition,a model was developed and validated to predict the effective compaction range.The results show that soil dry density increased rapidly during compaction grouting before being stabilized at a consistent level.As expected,it is positively correlated with grouting pressures(GPs)and negatively correlated with the distance from the injection point.At higher GPs,the difference in densification effect around the injection point after compaction grouting was significant.Interestingly,variations in ultimate dry density and peak earth pressures perpendicular to the injection direction exhibited axisymmetric behavior around the injection point when comparing the dry density and earth pressure results.Furthermore,soil densification resulted in a decrease in suction.However,no significant effect of GP on suction at different soil positions was observed.Moreover,compaction efficiency decreased with increasing distance from the injection point,showing a strong linear relationship.In addition,the model results for the effective compaction range were basically consistent with the extrapolated values from the experimental results. 展开更多
关键词 Compaction grouting Densification effect Dry density Void ratio Volumetric water content Unsaturated soil
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Simplified approaches for predicting the nonlinear load-displacement response of single pile and pile groups in unsaturated soils
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作者 Xinting Cheng Sai K.Vanapalli 《Journal of Rock Mechanics and Geotechnical Engineering》 2025年第5期3107-3124,共18页
A simplified analytical approach is proposed for predicting the load-displacement behavior of single piles in unsaturated soils considering the contribution from the nonlinear shear strength and soil stiffness influen... A simplified analytical approach is proposed for predicting the load-displacement behavior of single piles in unsaturated soils considering the contribution from the nonlinear shear strength and soil stiffness influenced by matric suction.This approach includes a Modified Load Transfer Model(MLTM)that can predict the nonlinear relationships between the shear stress and pile-soil relative displacement along the pile shaft,and between the pile base resistance and base settlement.The proposed model is also extended for pile groups to incorporate the interaction effects between individual piles.The analytical approach is validated through a comparative analysis with the measurements from two single pile tests and one pile group test.In addition,a finite element analysis using 3D modeling is carried out to investigate the behavior of pile groups in various unsaturated conditions.This is accomplished with a user-defined subroutine that is written and implemented in ABAQUS to simulate the nonlinear mechanical behavior of unsaturated soils.The predictions derived from the proposed analytical and numerical methods compare well with the measurements of a published experimental study.The proposed methodologies have the potential to be applied in geotechnical engineering practice for the rational design of single piles and pile groups in unsaturated soils. 展开更多
关键词 Unsaturated soils Matric suction PILE Pile group Load transfer model
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