Influence of temperature on the hydrothermal clay soils' shear strength of the Nizhne-Koshelevsky and Verkhne-Pauzhetsky thermal fields.

Nizhne-Koshelevskoe and Verkhne-Pauzhetskoe thermal fields are located in the south of Kamchatka, the first - within the Koshelevsky volcanic massif, the second - on the territory of the Pauzhetsky geothermal field. The first horizon from the surface in these fields is formed by clayey soils, that have been formed as a result of hydrothermal alteration of volcanic rocks. And in the natural conditions clayey soils are at temperatures reaching 100 &#176;C.Samples of undisturbed clay soils were taken within the thermal fields. The samples are characterized by a density of 1.29 - 1.42 g/cm3, rather high values of the weight moisture (90-110%), and temperatures of 50 - 70 &#176;C.The samples are dominated by clay minerals: kaolinite and mixed-layer - kaolinite-smectite, their content is about 75%. The other 25% are microcline, cristobalite, anatase, gypsum, pyrite, marcasite, quartz and alunite.For samples of undisturbed clay soils, direct shear tests were carried out at a temperature of 20 &#176;C and at a temperatures of the samples close to their natural temperatures (50&#8211;70 &#176;C). Thus, the values of cohesion and the angle of internal friction of the samples were determined.The obtained results can be interfered as follows: as a result of an increase in the temperature of clayey soils, the thickness of electric double layer on the surface of clay particles decreases. On the one hand, it leads to a decrease of cohesion value between the clay particles and the beginning of shear deformations at lower vertical loads. On the other hand, a smaller thickness of electric double layer brings particles closer to each other, which is the reason for an increasing angle of internal friction and shear resistance at higher vertical loads.

Download Full-text

Empirical formulae for electric double-layer repulsion between two arbitrarily inclined clay particles

Journal of Rock Mechanics and Geotechnical Engineering ◽

10.1016/j.jrmge.2018.08.005 ◽

2018 ◽

Vol 10 (6) ◽

pp. 1183-1189

Author(s):

Xiangyu Shang ◽

Juming Lu ◽

Lianfei Kuang ◽

Chen Yang ◽

Guoqing Zhou

Keyword(s):

Double Layer ◽

Electric Double Layer ◽

Clay Particles

Download Full-text

Variation of the Hydraulic Conductivity of Clayey Soils in Exposure to Organic Permeants

Civil Engineering Journal ◽

10.28991/cej-030936 ◽

2017 ◽

Vol 3 (11) ◽

pp. 1036 ◽

Cited By ~ 4

Author(s):

Hanane Mortezaei ◽

Mehran Karimpour Fard

Keyword(s):

Dielectric Constant ◽

Water Content ◽

Double Layer ◽

Clayey Soils ◽

Contamination Control ◽

Clay Particles ◽

Soil Plasticity ◽

Low Dielectric ◽

Constant Head ◽

Constant Head Method

Clayey soils are the most common material used in waterproofing and play an essential role in waste and contamination control. Permeability is a key parameter in such problems and its determination is needed in ensuring the satisfactory performance of the soil. Research has shown that a permeant fluid with a low dielectric constant can shrink the double layer around the clay particles which will, in turn, increase the permeability of the soil. In this paper, the permeability of two types of clay with different plasticity, exposed to the flow of water and methanol as polar and miscible solvents and gasoline and car oil as non-polar and immiscible solvents is investigated. In addition, the effect of soil properties such as plasticity and compaction water content on permeability of the samples is examined. To this end, soil samples are prepared and compacted at various water contents. Then, permeability tests are conducted according to the modified constant head method and the effects of parameters such as the fluid dielectric constant, water content of the samples and soil plasticity are examined. The results demonstrate that the lower dielectric constant of the organic fluid decreases the thickness of the double layer, providing more space for the flow of the permeant and as a result, the permeability of the clay increases. The reduction of the permeant dielectric constant from 80.4 to 2.28 led to a remarkable increase in soil permeability.

Download Full-text

The Role of Diffusion of Polymer Chains in the Mechanism of Adhesion and Autohesion of Rubbers

Rubber Chemistry and Technology ◽

10.5254/1.3542728 ◽

1957 ◽

Vol 30 (3) ◽

pp. 837-846 ◽

Cited By ~ 1

Author(s):

B. V. Deryagin ◽

S. K. Zherebkov ◽

A. M. Medvedeva

Keyword(s):

Mechanical Properties ◽

Double Layer ◽

Contact Area ◽

Electric Double Layer ◽

Contact Time ◽

Diffusion Processes ◽

The Other ◽

Shearing Strength ◽

True Contact Area ◽

True Contact

Abstract 1. The researches so far published on the autohesion of polymers do not make it possible to isolate the influence of the mechanical properties of rubbers, which determine the true area of contact, from the influence of polymer chain diffusion. 2. Studies of the autohesion of thin films of rubber applied by the drain-off method to quartz threads, in relation to the film thickness and contact time, show that for films less than 3.10−5 cm. thick the adhesion force is small and varies very little with contact time. This proves, on the one hand, that in this instance the contact area is small (which is obvious) and does not increase with time, and on the other hand, that diffusion processes play no part in the autohesion of films of this thickness. 3. The effects which depend on mechanical properties and on the specific interaction (per unit area of true contact) between specimens may be separated if the measured values of adhesion between all possible combinations of pairs of rubbers are compared both with their compatibilities, and with their autohesion. 4. The measurements of the adhesional shearing strength of combinations of different pairs of polymers, carried out for this purpose, showed that the results for Butyl rubber may be interpreted on the assumption that diffusion processes do not play any appreciable role and that the adhesion strength is determined both by the true contact area, which depends on the mechanical properties of the corresponding polymer specimens, and also by the influence of forces associated with the electric double layer. 5. For the other rubbers the results may be interpreted only on the assumption that diffusion processes play a significant part. For similar polarities, T12/T11>1 and for dissimilar polarities, T12/T11<1. 6. General conclusion : autohesion and mutual adhesion of rubbers is determined both by mechanical properties, which determine the true contact area, and by diffusional properties. The latter are by no means always decisive. The electric double layer also probably influences the adhesional shearing strength in some instances. It is even more likely to play a role in some cases in measurements of the work of separation of two layers.

Download Full-text

Prediction of the hydraulic conductivity of clays using the electric double layer theory

Canadian Geotechnical Journal ◽

10.1139/t99-052 ◽

1999 ◽

Vol 36 (5) ◽

pp. 783-792 ◽

Cited By ~ 30

Author(s):

Gopal Achari ◽

R C Joshi ◽

L R Bentley ◽

S Chatterji

Keyword(s):

Hydraulic Conductivity ◽

Double Layer ◽

Electric Double Layer ◽

Layer Model ◽

Clay Liners ◽

Overburden Pressure ◽

Clay Particles ◽

Concentration Of Ions ◽

Double Layer Model ◽

Double Layer Theory

A model to predict the hydraulic conductivity of consolidated clay, simulating clay liners compacted wet of optimum, is presented. The concept that clays exist as clusters and the electrical double layer theory are used to predict the hydraulic conductivity of clays for permeants of known composition. The model relates the physical properties of clays, such as its surface area, with the overburden pressure and the concentration of ions in the permeant. The model can be used to predict the hydraulic conductivity of bentonitic clays with monovalent as well as divalent exchangeable cations. The model is valid within the range of applicability of the Gouy-Chapman electric double layer theory. The variation in the number of clay particles per cluster with the consolidation pressure and concentration of ions in the permeant has been discussed. The model has been calibrated and verified using published experimental data. However, the model in its present form is valid only for homoionic clays and permeants with the same valency. With an increase in concentration of ions in the permeant, the precision of the model has been found to decrease. Key words: clay, clusters, hydraulic conductivity, double layer, model, permeant, concentration.

Download Full-text

Changes in the Strength Characteristics of Glinistx Soils under the Influence of Dynamic Forces

International Journal of Engineering and Advanced Technology - Regular Issue ◽

10.35940/ijeat.e9712.069520 ◽

2020 ◽

Vol 9 (5) ◽

pp. 639-643

Keyword(s):

Internal Friction ◽

Experimental Studies ◽

Sharp Decrease ◽

Friction Angle ◽

Strength Characteristics ◽

Clay Soils ◽

Angle Of Internal Friction ◽

Dynamic Forces ◽

The Impact ◽

Soil Indicators

In order to study in depth the impact of vibration on the strength characteristics of clay soils, as well as to develop methods that increase the strength characteristics and contribute to the elimination of seismic shrinkage deformations of clay soils, we conducted research in the field. In field experimental studies, the svaw-12 trailed, smooth vibration roller, manufactured in Germany, was used. We paid special attention to the further behavior of the soil after the vibration and made observations and measurements of soil indicators for two months. The experiments in the field with vibration column showed an increase of soil deformation with increasing duration of the fluctuations, i.e. there is a linear relationship between the increases in soil density on the duration of oscillations. In the process of vibration, there is a sharp decrease in the force of adhesion and the angle of internal friction, which is apparently associated with a violation of the structure of the soil and its compaction. And then at the end of the vibration process, over time, there is an increase in the adhesion (1.5-2 times) and the internal friction angle (1.2 times) of the soil, obviously as a result of the soil acquiring new strength and compaction under the influence of its own weight. This circumstance is also associated with the humidity state of the soil.

Download Full-text

Coffee grounds as a soil conditioner: Effects on physical and mechanical properties – II. Effects on mechanical properties

Polish Journal of Soil Science ◽

10.17951/pjss.2019.52.2.277 ◽

2019 ◽

Vol 52 (2) ◽

pp. 277

Author(s):

M-Naguib A. Bedaiwy ◽

Yasmine S. Abdel Maksoud ◽

Ahmed F. Saad

Keyword(s):

Mechanical Properties ◽

Internal Friction ◽

Initial Stress ◽

Calcareous Soil ◽

Seedling Emergence ◽

Physical And Mechanical Properties ◽

Clayey Soils ◽

Angle Of Internal Friction ◽

Coffee Grounds ◽

Resistance To Penetration

Applying coffee grounds (CG) to sandy, calcareous, and clayey soils resulted in notable effects on soil expansion, cracking, cohesion, internal friction, initial stress and resistance to penetration. In sand, expansion upon saturation was greater after wetting-and-drying cycles. Highest increases were 15.71%, 16.14% and 31.86% for sandy, calcareous and clayey soils, respectively. Effect of CG on cracking was negligible in sand and very slight (<1.0%) in the calcareous soil but marked in clay (14.18% at 10% CG). In sand, cohesion (c) increased significantly with CG up to the 10% content. Cohesion increased by 2.5-folds and 4.5-folds at 5% and 10% CG, respectively. The presence of fine CG grains among larger sand particles, boosted microbial activities, and the resulting cementing and binding effects resulted in increased cohesion. For calcareous soil, cohesion rose from 0.04 kg∙cm-2 to 0.13 kg∙cm-2 as CG increased from 0% to 15%. In clay, maximum cohesion (0.20 kg∙cm-2) was associated with the 10% CG and was highest of all soils. In sand, the angle of internal friction (φ) decreased notably as CG increased from 5% to 10% but there was no consistent pattern in any of the soils. An increase in initial stress (pi) was observed between 0% and 10% CG in sand and between 0% and 15% in calcareous soil while clay showed no particular trend. Patterns of pi were, thus, consistent with those of cohesion for all soils. Resistance to penetration increased substantially with CG in sand. The effect in calcareous and clayey soils took an opposite trend to that of sand and resistance was generally higher in calcareous soil. Overall effects of CG on resistance were desirable in all soils as far as agriculture (seedling emergence, crop growth, irrigation, etc.) is concerned.

Download Full-text