Evaluation of the mechanical anisotropy of lacustrine smectite clays by triaxial test analysis

2022 ◽  
Author(s):  
Jubier Alonso Jiménez-Camargo ◽  
Dora Carreon-Freyre
Keyword(s):  
Water Content ◽  
Mechanical Response ◽  
Clayey Soil ◽  
Mechanical Anisotropy ◽  
Degree Of Saturation ◽  
Triaxial Tests ◽  
Particle Deformation ◽  
Relevant Variable ◽  
Pressure Equalization

Abstract This paper describes the role of fabric anisotropy during clayey soil deformation. A set of triaxial tests was performed on vertical and horizontal specimens of undisturbed smectite lake sediments from Jurica, Queretaro in Mexico. The results allowed to analyze the influence of bedding and discontinuities on the mechanical behavior of Jurica clays after failure. Tests with applied low strain rates allowed pore pressure equalization within specimens with different gravimetric water content and degree of saturation. Shear failure results of undrained tests showed that deformation distributes differently in both horizontal and vertical directions and that stress may be dissipated by pore collapses, fractures and particle deformation. The experimental evidence suggests that microfabric is a relevant variable in the overall mechanical response of clayey sediments that depends on the natural fabric (bedding and discontinuities), mineralogy, and water content. A detailed analysis of Young´s Moduli (E) showed the high variability of this parameter from 108 to 409 kg/cm2 (calculated at 30% of σdmax) and its dependence on the orientation of the specimen and the water content. In addition, p’-q’ graphs illustrate the relevance of considering mechanical anisotropy in clays and provide further insights to understand the role of smectites in progressive shear deformation.

scholarly journals ROLE OF MAGENISUM, WATER CONTENT AND FRETILIZERS ON SOME ELEMENTS AVAILABILITY IN CLAYEY SOIL

2013 ◽  
Vol 4 (2) ◽  
pp. 71-83
Author(s):  
S. A. Hammad ◽  
T. M. El-Zehery ◽  
Y. S. El-Arquan ◽  
Marwa G. El-Moogy
Keyword(s):  
Water Content ◽  
Clayey Soil

scholarly journals Modelling of oedometer tests on pellet-powder bentonite mixtures to support mock-up test analysis

2020 ◽  
Vol 195 ◽  
pp. 04004
Author(s):  
Arisleidy Mesa Alcantara ◽  
Nadia Mokni ◽  
Enrique Romero ◽  
Sebastià Olivella
Keyword(s):  
Pore Size ◽  
Water Content ◽  
Mechanical Response ◽  
Degree Of Saturation ◽  
Test Analysis ◽  
Porosity Level ◽  
Consequent Reduction ◽  
High Level ◽  
Mass Basis ◽  
Oedometer Tests

Bentonite mixtures of MX-80 (80% of high-density pellets and 20% of bentonite powder on a mass basis) have been recently proposed as a candidate material for sealing deep geological disposals of high-level radioactive waste. A loading/unloading oedometer test at constant water content has been performed on this mixture, which has been modelled using the finite element Code_Bright. The constitutive model used to represent the mechanical response is the Barcelona Expansive Model (BExM), since a multi-modal pore size distribution characterises the pore network of the mixture. During compression at constant water content, an increase in the degree of saturation and a consequent reduction of suction is induced. Consequently, two competing effects occur at different pore-size scales: (a) compression due to mean net stress increase; and (b) expansion on induced suction reduction that mainly affects the micro-porosity level inside aggregates. A sensitivity analysis has been performed to explore these effects, in which the elastic compressibility parameter at the micro-porosity scale for changes in mean effective stress plays an important role.

Use of Stiffness for Evaluating Compactness of Cohesive Pavement Geomaterials

2003 ◽  
Vol 1849 (1) ◽  
pp. 11-19 ◽  
Author(s):  
Phillip S. K. Ooi ◽  
Jianping Pu
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Volume Change ◽  
Degree Of Saturation ◽  
Unit Weight ◽  
Soil Stiffness ◽  
Soil Plasticity ◽  
Dry Unit Weight ◽  
Swell Potential

There has been a recent push toward adoption of in-place soil stiffness as a means of assessing compactness of pavement geomaterials. From a series of low strain GeoGauge stiffness measurements made under controlled laboratory conditions on compacted silts, the variation of stiffness with water content, dry unit weight, degree of saturation, volume change upon wetting, shear strength, and soil plasticity is discussed. In general, the GeoGauge stiffness is not directly related to dry unit weight, and it peaks dry of optimum and decreases upon wetting. Soil specimens with a large stiffness also tend to be stronger, but they also tend to swell more upon wetting, implying that the shrink–swell potential is not optimized if stiffness is. These results help advance the understanding of the role of stiffness in assessing compactness of cohesive geomaterials.

Emploi d'une méthode psychrométrique dans des essais triaxiaux sur un limon remanié non saturé

1978 ◽  
Vol 15 (4) ◽  
pp. 501-509 ◽  
Author(s):  
Jean-Claude Verbrugge
Keyword(s):  
Water Content ◽  
Degree Of Saturation ◽  
Breaking Stress ◽  
Triaxial Tests ◽  
Peltier Effect ◽  
Interstitial Pressure ◽  
Experimental Relation

This paper summarizes the results obtained with triaxial tests made on an unsaturated loam. The originality of the tests proceeds from the use of a Peltier effect psychometric probe for the measurements of interstitial pressure. This had made it possible to study the variations of the breaking stress in terms of water content and suction of soil. The coefficient χ of Bishop at rupture was also studied in terms of those variables and of the degree of saturation. An experimental relation between χ and |s| is proposed.

Experimental study on volumetric behaviour of Maryland clay and the role of degree of saturation

2014 ◽  
Vol 51 (12) ◽  
pp. 1449-1455 ◽  
Author(s):  
Glen J. Burton ◽  
Daichao Sheng ◽  
David Airey
Keyword(s):  
Water Content ◽  
State Parameter ◽  
Degree Of Saturation ◽  
State Variable ◽  
Optimum Water Content ◽  
Constant Suction ◽  
Compaction Energy ◽  
Oedometer Tests ◽  
Compression Line

In this paper, the volume change behaviour of Maryland clay compacted on the wet side of standard Proctor optimum water content (with lower compaction energy) is studied in reference to the saturated reconstituted state. Oedometer tests over a range of suctions and vertical stresses have been carried out, and the results have shown that the compression index reaches a peak (approximately twice that of the reconstituted material) and then gradually reduces to the reconstituted value as the stress level is increased. The results are analyzed in a framework where the degree of saturation is treated as a state parameter and controls the slope of the unsaturated normal compression line. Tests conducted under constant suction and constant water content have been used to demonstrate the effectiveness of using the degree of saturation as a state variable.

Inclusion of specific water volume within an elasto-plastic model for unsaturated soil

1996 ◽  
Vol 33 (1) ◽  
pp. 42-57 ◽  
Author(s):  
S J Wheeler
Keyword(s):  
Water Content ◽  
Unsaturated Soil ◽  
Critical State ◽  
Constitutive Models ◽  
Degree Of Saturation ◽  
Triaxial Tests ◽  
Water Volume ◽  
Plastic Model ◽  
Elasto Plasticity ◽  
Soil Behaviour

Existing elasto-plastic critical state constitutive models for unsaturated soil provide no information on the variation of water content or degree of saturation. These models cannot therefore, for example, be used to predict unsaturated soil behaviour during undrained loading, when the variation of suction is determined by the requirement that water content remains constant. This problem has been tackled by extending an existing elasto-plastic model to include relationships describing the variation of specific water volume (the volume of water and solids in an element of soil containing unit volume of solids). The proposed form of the variation of specific water volume was based on consideration of the soil fabric, resulting in a coupled form of elasto-plastic behaviour. Predictions from the elasto-plastic model showed good agreement with the experimental results from suction-controlled triaxial tests on unsaturated samples of compacted speswhite kaolin. Normal compression lines for specific water volume at different values of suction were well predicted, as was the variation of specific water volume during wetting. Critical state values of specific water volume were slightly underestimated, but test paths for both drained and undrained shearing were predicted with reasonable success. Key words: compacted clays, constitutive model, critical state, elasto-plasticity, triaxial tests, unsaturated.

The Role of Mechanical Tension in Neurons

2010 ◽  
Vol 1274 ◽  
Author(s):  
Taher Saif ◽  
Jagannathan Rajagopalan ◽  
Alireza Tofangchi
Keyword(s):  
Mechanical Response ◽  
Mechanical Forces ◽  
Active Tension ◽  
Mechanical Tension ◽  
Deformation Response ◽  
Linear Force ◽  
Tension Regulation ◽  
Over Time

AbstractWe used high resolution micromechanical force sensors to study the in vivo mechanical response of embryonic Drosophila neurons. Our experiments show that Drosophila axons have a rest tension of a few nN and respond to mechanical forces in a manner characteristic of viscoelastic solids. In response to fast externally applied stretch they show a linear force-deformation response and when the applied stretch is held constant the force in the axons relaxes to a steady state value over time. More importantly, when the tension in the axons is suddenly reduced by releasing the external force the neurons actively restore the tension, sometimes close to their resting value. Along with the recent findings of Siechen et al (Proc. Natl. Acad. Sci. USA 106, 12611 (2009)) showing a link between mechanical tension and synaptic plasticity, our observation of active tension regulation in neurons suggest an important role for mechanical forces in the functioning of neurons in vivo.

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