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A grading parameter for evaluating the grading-dependence of the shear stiffness of granular aggregates

Particuology 2018年第1期16卷 193-198页

作者： Yifei Sun Yang Shen Chen Chen Key Laboratory of Ministry of Education for Ceomechanics and Embankment Engineering Jiangsu Research Center for Ceotechnical Engineering Technology Hohai University Nanjing 210098 China

To capture the grading-dependence of the shear stiffness of heterogeneous granular aggregates, a new grading parameter that considered the size distribution of the entire aggregates was developed. Both the coefficient of uniformity and median particle size decreased with increasing the grading parameter. A general increase of the shear stiffness with increasing the grading parameter was observed. Compari- son with experimental results revealed that the proposed grading parameter had a stronger correlation with the material constants of Hardin＇s stiffness formula than the coefficient of uniformity, which is a traditional grading parameter.

关键词： shear stiffness Grading Coefficient of uniformity Particle size

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Influence of anisotropic stress path and stress history on stiffness of calcareous sands from Western Australia and the Philippines

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第1期14卷 197-209页

作者： Huan He Siyue Li Kostas Senetakis Matthew Richard Coop Songyu Liu Institute of Geotechnical Engineering Southeast UniversityNanjing210096China Department of Architecture and Civil Engineering City University of Hong KongKowloonHong KongChina Department of Architecture and Civil Engineering Yeung Kin Man Academic BuildingBlue Zone 6/FCity University of Hong KongKowloonHong KongChina Department of Civil Environmental and Geomatic EngineeringUniversity College LondonLondonUK

Investigation of dynamic properties of carbonate/calcareous soils is important in earthquake and offshore engineering as these soils are commonly encountered in large-scale projects related with energy geomechanics and land *** this study,the stiffness and stiffness anisotropy of two types of calcareous sands(CS)from the Western Australia and the Philippines were examined using bender elements configured in different directions in stress path *** measurements were taken on specimens subjected to constant p’compression/extension and biaxial stress paths and additional tests were performed on three types of silica sands with different geological origins and particle shapes,which were used as benchmark materials in the *** with the three brands of silica sands,the stiffness of the CS was found to be more significantly influenced by anisotropic loading;an important observation of the experimental results was that stress anisotropy had different weighted influences on the stiffness in different directions,thus influencing stiffness *** were made between the specimens subjected to complex loading paths,and respected model parameters as suggested from published expressions in the *** comparisons further highlighted that calcareous soils have different responses in terms of stiffness,stiffness anisotropy and loading history,compared with that of silica-based sands.

关键词： Calcareous soils Dynamic properties shear stiffness Stress anisotropy Stress history

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Characteristics of root-permeated soil under simple-shear and direct-shear conditions

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Journal of Mountain Science 2023年第8期20卷 2422-2435页

作者： CHEN Jing-yi CHEN Xiao-qing SONG Dong-ri LV Ming GUO Han-qing SADEGHI Hamed Laboratory of Mountain Hazards and Earth Surface Process/Institute of Mountain Hazards and Environment Chinese Academy of SciencesChengdu 610299China University of Chinese Academy of Sciences Beijing 100049China Department of Civil Engineering Sharif University of TechnologyTehran ***Iran

The simple-shear condition is closer to reality than the direct-shear condition for simulating the mechanical behavior of vegetated soil slope under shallow ***,study on simple-shear characteristics for vegetated slope is still insufficient,and there lacks intuitive comparison of characteristics between these two shear *** this study,large-scale simple-shear and direct-shear experiments were conducted on soil permeated by roots of Amorpha fruticosa to investigate the shear strength and *** stress-displacement relationship of each sample was obtained and further normalized to unify the influence of root *** results reveal that the direct-shear condition overestimates the shear strength of root-permeated soils(by 41%)and thus the estimation of slope stability based on the parameters of direct-shear condition is not ***,the initial stiffness of root-permeated soil under simple-shear condition is 34%lower than that under direct-shear *** higher strength and stiffness under direct-shear condition are caused by the following reasons:the shear plane does not have the lowest strength,the shear area is decreasing,and the shear zone is *** significant deformation(lower stiffness)revealed by the simple-shear condition facilitates the application of early warning for vegetated shallow landslides.

关键词： Simple-shear condition Direct-shear condition Root-permeated soil shear strength shear stiffness Shallow landslide

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Freezing and thawing effects of sand-silt mixtures on elastic waves

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Research in Cold and Arid Regions 2013年第4期5卷 418-424页

作者： MinGu Kang JongChan Kim Jung-Hee Park Jong-Sub Lee School of Civil Environmental and Architectural Engineering Korea University

Freezing and thawing during the winter season change soil properties such as density. The density change in the particulate media influences soil stiffness. In addition, freezing of partially or fully saturated soils changes the soil matrix from a particulate media to a continuum. The goal of this study is to investigate the cyclic freezing and thawing effects on elastic waves. Sand-silt mixtures with 10% silt fraction in weight and 40% saturation are prepared. The sand-silt mixtures are placed in a nylon cell, onto which a pair of bender elements and a pair of piezoelectric disk elements are installed for the measurement of shear and compressional waves, respectively. The temperature of the mixtures decreases from 20 ℃ to -10 ℃ to freezing. The frozen sample is gradually thawed at room temperature （20 ℃）, These freezing-thawing processes are repeated three times. The test result shows that the shear and compressional wave velocities significantly increase when the specimen is frozen. When the temperature is greater than 0 ℃, the elastic wave velocities are lower during thawing than during freezing due to soil structure change. This study demonstrates that soil strucre change during the winter season may be effectively estimated from elastic waves.

关键词： compressional waves freezing frozen soil shear stiffness shear waves thawing

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Human Eosinophil Cell Manipulation by Optical Tweezers

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Open Journal of Biophysics 2024年第3期14卷 330-338页

作者： Pavel Yale Jean Michel Edoukoua Konin Abadê Ange-Boris N’guessan Michel Abaka Kouacou Jérémie T. Zoueu Laboratoire dInstrumentation Image et Spectroscopie (L2IS) Institut National Polytechnique Houphout-Boigny (INPHB) Yamoussoukro Cte dIvoire Laboratoire de Chimie et de Physique Appliques Sciences et Techniques Universit Alassane Ouattara Bouak Cte dIvoire

In this work, lateral deformation of human eosinophil cell during the lateral indentation by an optically trapped microbead of diameter 4.5 µm is studied. The images were captured using a CCD camera and the Boltzmann statistics method was used for force calibration. Using the Hertz model, we calculated and compared the elastic moduli resulting from the lateral force, showing that the differences are important and the force should be considered. Besides the lateral component, the setup also allows us to examine the lateral cell-bead interaction. The mean values of the properties obtained, in particular the elastic stiffness and the shear stiffness, were Eh = (37.76 ± 2.85) µN/m and Gh = (12.57 ± 0.32) µN/m. These results show that the lateral indentation can therefore be used as a routine method for cell study, because it enabled us to manipulate the cell without contact with the laser.

关键词： Optical Tweezers Human Eosinophil Cell Indentation shear stiffness

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