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Experimental research on the development of residual strain in seasonal frozen soil under freezing-thawing and impact type traffic loads

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Earthquake Engineering and Engineering Vibration 2021年第2期20卷 335-345页

作者： Liu Tianhua Wang Miao Harbin University of Science and Technology Harbin 150080China Heilongjiang Institute of Technology Harbin 150050China

Vehicle load is among the main factors affecting the deformation of subgrade *** this research study,the concept of impact type traffic load is introduced to investigate the effects of vehicle load based on the dynamic stress and displacement time histories acquired from seasonal frozen subgrade *** freezing-thawing and dynamic triaxial tests and considering the amplitude and loading sequence of impact type traffic load,the residual deformation characteristics of subgrade soil under impact type traffic loads and freezing-thawing cycles is *** was found that under impact type traffic load,the residual deformation of soils increased sharply as the amplitude of impact type traffic load *** was also found that the increase in the amplitude of impact type traffic load led to the increase of residual deformation in a scale of power and exponential *** amplitudes of impact type traffic load affect the development stress-strain path of the residual *** the soil experienced the proper amount of pre-vibration of the light load,residual deformation decreased by 15%.After freezing-thawing,the residual strain of soil increased as the amplitude of the impact type traffic loads ***,when the amplification effect of freezing-thawing on the residual strain was basically stable,the residual deformation increased by about 10%.The peak impact type traffic load had a large effect on soil deformation after the freezing-thawing process,leading to the observation that of the earlier the peaks,the stronger the effect of *** the soil was subjected to preloading with a small load,the influence of the freezing-thawing cycles gradually *** results may be useful in preventing and controlling the risk of subgrade soil failure when construction takes place spring thaw periods.

关键词： impact type traffic load freezing-thawing dynamic triaxial test loading sequence residual strain

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Development of pot-cover effect apparatus with freezing-thawing cycles

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Science China(Technological Sciences) 2019年第9期62卷 1636-1648页

作者： LUO Ting CHEN Han YAO YangPing WANG NaiDong QU Xiao School of Transportation Science and Engineering Beihang University

‘Pot-cover effect’ refers to the phenomenon of moisture accumulation beneath the pavement under condensation or desublimation because the vapor transfer in the soil is blocked by the pavement. To study this phenomenon in the laboratory, we have developed the pot-cover effect apparatus with freezing-thawing cycles(PEAFC), which consists of three parts, namely, the vapor transfer system, the temperature control system, and the temperature and water content monitoring system. The major functions of this apparatus include: simulation of both vapor transfer and freezing-thawing cycling in the soil, real-time monitoring of the temperature and the water content in soil samples, and one-dimensional heat and moisture transfer in the samples. The FDR(frequency domain reflectometry) sensors of the apparatus are calibrated and a calibration formula is proposed to eliminate the water content measurement errors induced by temperature changes. Constant temperature difference tests and a freezing-thawing cycling test are conducted with the apparatus. Results indicate that the apparatus can control the water replenishment in the soil samples, monitor the vapor transfer in the samples in real time, and simulate the vapor transfer process under the condition of the freezing-thawing cycling in the soil. These tests verify the effectiveness and reliability of the apparatus, which indicates that the development purpose is achieved.

关键词： pot-cover effect apparatus vapor transfer freezing-thawing cycle water content

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Effect of pH,temperature and freezing-thawing on quantity changes and cellular uptake of exosomes

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Protein & Cell 2019年第4期10卷 295-299页

作者： Yirui Cheng Qingyu Zeng Qing Han Weiliang Xia School of Biomedical Engineering and Med-X Research Institute Shanghai Jiao Tong University Shanghai 200030 China. School of Biomedical Engineering and Med-X Research Institute Shanghai Jiao Tong University Shanghai 200030 China. wlxia@***.

Exosomes are cup-shaped small(30-150 nm)extracellular vesicles with the structure of lipid bilayer membrane(Tkach and Thery,2016)containing proteins,mRNAs and micro-RNAs that mediate intercellular communication(Valadi et al.,2007).Unlike other extracellular vesicles,exosomes are released into the extracellular space when the multivesicular bodies(MVBs)fuse with the plasma membrane(Colombo et al.,2014).

关键词： pH temperature freezing-thawing

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Centrifugal and field studies on water infiltration characteristics below canals under wetting-drying-freezing-thawing cycles

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Journal of Central South University 2021年第5期28卷 1519-1533页

作者： ZHU Rui CAI Zheng-yin HUANG Ying-hao ZHANG Chen GUO Wan-li ZHU Xun Geotechnical Engineering Department Nanjing Hydraulic Research InstituteNanjing 210024China College of Civil and Transportation Engineering Hohai UniversityNanjing 210098China

Seepage is one of the main causes for the deformation and instability of canal slopes in Xinjiang,*** this study,centrifugal model tests under wetting-drying(WD)and wetting-drying-freezing-thawing(WDFT)cycles were performed to investigate the water infiltration characteristics below a *** results show that the shallow soil of the canal models was fully saturated in the wetting *** with the canal model under the WD cycles,the canal model under the WDFT cycles had larger saturated areas and a higher degree of saturation below the canal top after each cycle,indicating that the freezing-thawing(FT)process in the WDFT cycles promoted the water infiltration behavior below the canal *** cracks on the surface of the canal model under the cyclic action of WDFT developed further and had a higher connectivity,which provided the conditions for slope instability from a transverse tensile crack running through the canal *** this basis,a field test was conducted to understand the water infiltration distribution below a typical canal in Xinjiang,China,which also verified the accuracy of the centrifugal *** study provides a preliminary basis for the maintenance and seepage treatment of canals in Xinjiang,China.

关键词： wetting-drying freezing-thawing water infiltration crack canals centrifugal model test

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Response Relationship between the Seasonal freezing-thawing Process of Soil and Spatial Factor Changes in the Dayekou Basin of the Qilian Mountains

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Open Journal of Ecology 2018年第8期8卷 417-431页

作者： Yun Niu Jinling An School of Urban and Environmental Science Huaiyin Normal University Huaian China Administration of Qilian Mountain National Nature Conservation in Gansu Zhangye China

Objective: In this study, the influence and response relationship between the seasonal freezing-thawing process of soil and the spatial factor changes in the management and utilization of water resource processes were explored. Methods: The monitoring equipment in this study was arranged at different altitudes, gradients, and slope directions, such as the typical forest sample area in the Dayekou Basin of the Qilian Mountains. The spatial variation characteristics of the seasonal freezing-thawing process of the soil were analyzed, and a regression model was established. Results: 1) The results of this study determined that the rate of the soil’s freezing increased with the altitude in a trend of volatility. However, the rate of the thawing of the frozen soil was found to have an opposite trend. The variation degree of the freezing-thawing process increased with the altitude in a trend of volatility. The end time of the approximate soil freezing with altitude increased in a volatility trend ahead of schedule. However, the opposite was observed in the thawing rate of the frozen soil;2) The rate of the soil’s freezing under the mosses of the spruce forest at an altitude of 3028 m was found to be the lowest. However, in the sub-alpine scrub forest at an altitude of 3300 m, a maximum in the spatial ordering was observed, with an average of 1.9 cm·d-1. The thawing rate of the frozen soil in scrub-spruce forest at an altitude of 3300 m was found to be minimal. However, in the sunny slope grassland at an altitude of 2946 m, a maximum in the spatial ordering was observed, with an average of 1.5 cm·d-1. In the spatial ordering of the variation degree of the process of freezing-thawing with an average of 1.2, the scrub-grassland at an altitude of 2518 m was found to be the lowest, and the scrub-spruce forest at an altitude of 3195 m was also low;3) The soil freezing began on approximately October 20th, and the rate of soil freezing gradually became reduced. The arrival time of

关键词： freezing-thawing Spatial Factor Seasonal Frozen Soil Dayekou Basin of the Qilian Mountains

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Numerical Simulation on Climate Effects of freezing-thawing Processes Using CCM3

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Research in Cold and Arid Regions 2008年第1期 68-79页

作者： Chenghai Wang Guodong Cheng Aijun Deng Wenjie Dong State Key Laboratory of Frozen Soil Engineering Cold and Arid Regions Environmental and Engineering Research In-stituteChinese Academy of SciencesLanzhou Gansu 730000China State Key Laboratory of Cryosphere Sciences Cold and Arid Regions Environmental and Engineering Research Insti-tuteChinese Academy of SciencesLanzhou Gansu 730000China Department of Meteorology The Pennsylvania State UniversityUniversity ParkPA 16802 State Key Laboratory of Earth Surface Processes and Ecology Resource Beijing Normal UniversityBeijing 100875China

A parameterization of soil freezing-thawing physics for use in the land-surface model of the National Center for Atmospheric Research(NCAR) Community Climate Model(CCM3) is developed and *** new parameterization scheme has improved the representation of physical processes in the existing land surface *** simulations using CCM3 with improved land-surface processes and with the original land-surface processes are compared against the NCEP *** is found that the CCM3 version using the improved land surface model shows significant improvements in simulating precipitation in China during the summer season,the general circulation over East Asia,and wind fields over the Tibet *** the summer season,the improved model was able to better simulate the Indian summer monsoon components,including the mean northerly wind in the upper troposphere and mean southerly wind in the lower troposphere.

关键词： freezing-thawing climate effect Tibet Plateau

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Effect of freezing-thawing Process on Wetland Soil Iron

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地学前缘 2009年第S1期16卷 237-237页

作者： Yuanchun Zou,Xianguo Lu,Ming Jiang,Xiaofei Yu Key Laboratory of Wetland Ecology and Environment,Northeast Institute of Geography and Agroecology,Chinese Academy of Sciences,Changchun 130012,China.

The iron concentrations of snows,semi-melting snows,snowmelts,and ditch waters were observed in four typical microhabitats,Carex lasiocarpa marsh(Ⅰ), Calamagrostis angustifolia wet meadow(Ⅱ),dry land (Ⅲ)and paddy field(Ⅳ),of Sanjiang Plain Wetland, Northeast *** sample was collected from three sites of one microhabitat,mixed together, filtrated with 0.45μm membrane,and tested using atomic absorption spectrometry(AAS)for iron *** iron concentrations of soil solutions were investigated as *** soil solution was in-situ extracted by negative pressure,filtrated with 0.45μm membrane,and tested using AAS,too. The results showed that the wet precipitation of iron from snow were little to *** loss of iron was attributed to the interaction of water and soil surface. The iron concentrations of snowmelts were 7.4,15,

关键词： freezing-thawing process iron wetland soil Sanjiang Plain

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Effect of Fly Ash on Frost-Resistance and Chloride Ions Diffusion Properties of Marine Concrete

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China Ocean Engineering 2009年第2期23卷 367-377页

作者：杨文武钱觉时章一颖 College of Materials Science and Engineering Chongqing University College of Civil Engineering and Architecture Dalian Nationalities University

It is necessary to pay more attention to the durability of concrete undergoing freeze-thaw cycles and seawater attack *** are the effects of water-binder ratio,fly ash（FA）contents and air-entraining agent on resistance to frost and chloride diffusion of marine concrete blended with FA in natural *** results show that fly ash does not improve the frost resistance of concrete but can improve its resistance to chloride diffusion by addition of less than 30%.The resistance to frost and chloride diffusion of FA concrete can be improved with the decrease of water-binder ratio,and FA may improve both of them simultaneously only being mixed with air-entraining agent.A ratio（named as R）of the frost-resisting durability factor to chloride diffusion coefficient can be used to evaluate the durability of marine *** electron microscope（SEM）analyses are consistent with the evaluations by the value of R.

关键词： fly ash marine concrete freezing-thawing chloride ions diffusion assessment method

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Greenhouse Gas Emissions from Northeast China Rice Fields in Fallow Season

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Pedosphere 2007年第5期17卷 630-638页

作者： LIANG Wei SHI Yi ZHANG Hua YUE Jin HUANG Guo-Hong Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 （China） Graduate School of the Chinese Academy of Sciences Beijing 10005g （China） College of Resources and Environment Huazhong Agricultural University Wuhan 430070 （China）

CH4, N2O and CO2 emissions from northeast Chinese rice fields were measured in the fallow season （November to March） to investigate the effects of freezing-thawing on the emissions. Both CH4 emission from and atmospheric CH4 oxidation by the soil occurred, but the flux was small. During the fallow season, rice fields acted as a minor source of atmospheric CH4, which accounted for about 1% of the CH4 emission during the rice growing period. The field was also a substantial source of atmospheric N20, which ranged between 40 to 77 mg m-2 and eu=counted for 40%-50% of the annual N20 emission. The largest N20 flux was observed in the thawing period during the fallow season. Laboratory incubation tests showed that the largest N20 flux came from the release of N20 trapped in frozen soil. Tillage and rice straw application （either mulched on the soil surface or incorporated in the soil） stimulated the CH4 and CO2 emissions during the fallow season, but only straw application stimulated N2O emission substantially.

关键词： CH4 CO2 freezing-thawing N2O rice field

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Preparation and Characterization of Nano-hydroxyapatite/polyvinyl Alcohol Gel Composites

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Journal of Wuhan University of Technology(Materials Science) 2010年第3期25卷 474-478页

作者：潘育松 Department of Material Science & Engineering Anhui University of Science and Technology

Nano-hydroxyapatite reinforced poly（vinyl alcohol） gel（nano-HA/PVA gel） composites has been proposed as a promising biomaterial,especially used as an articular cartilage repair *** this paper,nano-HA/PVA gel composite was prepared by in situ synthesis method and incorporation with freeze-thaw cycle *** microstructure and morphology were investigated by X-ray diffraction,TEM,SEM and *** results showed that the size of HA particles synthesized in PVA solution was on the nanometer *** the size and crystallinity of HA particles synthesized in PVA solution decreased compared with that of HA synthesized in distilled *** nano-HA particles were distributed in PVA matrix uniformly due to the effect of PVA solution as a dispersant while low content of HA particles in the *** the contrary,with high content of nano-HA particles in the composites,the particles tended to *** result of FT-IR analysis indicated that the chemical bond between nano-HA particles and PVA matrix *** conformation and degree of tacticity of PVA molecule changed because of the addition of HA ***,the interfacial strength of the composites was improved due to the interaction between nano-HA particle and PVA matrix and this was beneficial to improving the mechanical properties of the composites.

关键词： nano-HA/PVA gel composites freezing-thawing microstructure morphology

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