scholarly journals The Influence of Specimen Geometry and Loading Conditions on the Mechanical Properties of Porous Brittle Media

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7144
Author(s):  
Anatoly M. Bragov ◽  
Andrey K. Lomunov ◽  
Leonid A. Igumnov ◽  
Aleksandr A. Belov ◽  
Victor A. Eremeyev

Dynamic tests of fine-grained fired dioxide-zirconia ceramics under compression under uniaxial stress conditions were carried out. The influence of the specimen length on the obtained strength and deformation properties of ceramics is investigated. The thickness of the specimen has a significant impact on the course of the obtained dynamic stress–strain diagrams: short specimens have a much more sloping area of active loading branch. The main contribution to the modulus of the load branch resulting from tests of brittle porous media is made by the geometry of the specimens and the porosity of the material. When choosing the length of specimens for dynamic tests, the optimal geometry of the tested specimens is preferable in accordance with the Davies–Hunter criterion, when the contributions of axial and radial inertia are mutually compensated, and the contribution of the effects of friction in the resulting diagram is minimal. When choosing the geometry of specimens of brittle porous media, the structure of the material should be taken into account so that the size of the specimen (both length and diameter) exceeds the size of the internal fractions of the material by at least five times.

1973 ◽  
Vol 10 (4) ◽  
pp. 571-580 ◽  
Author(s):  
J. F. Nixon ◽  
N. R. Morgenstern

If a fine grained soil is thawed under undrained conditions, in general an effective stress exists in the soil skeleton. This effective stress is termed the residual stress. In ice-rich soil the residual stress may be zero, but various combinations of stress and thermal histories can result in significant residual stresses being generated upon thawing.A simple procedure for measuring the residual stress is described and the method is employed to obtain values for the residual stress in natural and reconstituted samples of frozen soil. The residual stress is found to be dependent on the void ratio in the thawed undrained condition. A profile of the residual stress with depth is given for the natural permafrost samples that have been tested.Some implications of the residual stress in practice are discussed, with particular emphasis on the undrained strength and deformation properties of thawed permafrost.


2019 ◽  
Vol 945 ◽  
pp. 85-90 ◽  
Author(s):  
E.G. Karpikov ◽  
N.P. Lukutsova ◽  
E.A. Bondarenko ◽  
V.V. Klyonov ◽  
A.E. Zajcev

Micro-fillers based on natural mineral wollastonite, modifying fine-grained concrete and improving its physical and mechanical characteristics, are developed and studied. The influence of the most common stabilizers on the aggregate stability of wollastonite-based microdispersed systems in the aquatic dispersion environment is considered. The optimal parameters, ensuring the production of micro-fillers in the form of stable suspensions, are developed. The application efficiency of the wollastonite-based filler due to its micro-reinforcing properties is revealed. These properties are specified by the formation of needle-shaped crystals by the ultrasonic dispersion in the aquatic environment, chemically related to cement-containing raw materials and contributing to the active selective adsorption of the binder hydration products. It has a significant influence on the rheological parameters of cement composites, on structure formation, as well as on their strength and deformation properties.


Author(s):  
A. V. Dolgova ◽  
G. V. Nesvetaev

Objectives Reliability and durability of structures using materials with various properties (plaster coatings, cement glue, new concrete during repair and restoration of structures, etc.) largely depends on the adhesion of the layers and the deformation properties of the coatings. To obtain the required properties of materials used for coatings, modifiers based on polymers and low-modulus inclusions are introduced into the composition of new concretes, for example, entrained air. The aim of the work is to identify some patterns of change in the properties of concrete with the joint introduction of these modifiers.Method Experimental determination of the tensile strength in bending, compression, E-modulus, adhesion to the concrete base by standard methods.Result The influence of separate and joint introduction of dispersible polymer powders and various low-modulus inclusions into the composition of fine-grained concrete has been established.Conclusion The joint introduction to the composition of fine-grained concrete of various low-modulus inclusions and redispersible polymer powders provides a reduction in the stress level during forced deformations due to the different effects additives on the strength and deformation properties and contributes to increased adhesion to the concrete. 


1992 ◽  
Vol 27 (16) ◽  
pp. 4429-4438 ◽  
Author(s):  
G. S. A. M. Theunissen ◽  
J. S. Bouma ◽  
A. J. A. Winnubst ◽  
A. J. Burggraaf

1986 ◽  
Vol 23 (1) ◽  
pp. 87-93 ◽  
Author(s):  
Maurice B. Dusseault ◽  
Matthias Loftsson ◽  
David Russell

Samples of eastern black shale (Kettle Point oil shales, Ontario) were subjected to extensive mineralogical and geomechanical tests. We prove that the mineralogy, as measured by the ratio of quartz to illite, controls strength and deformation properties, and the organic material plays no significant role. The reason is that increasing clay content dilutes the rigid quartz–quartz grain contacts that are responsible for the high strengths and stiff behavior. Tests of temperature effects on point load strength of another low organic content oil shale confirm that organic matter is not important to mechanical properties in matrix-supported shales. Key words: shale, mineralogy, Brazilian test, triaxial strength, organic content, slake durability, thermogravimetry.


Author(s):  
Hamed Mahdipanah ◽  
Askari Tashakori ◽  
Samad Emamgholizadeh ◽  
Eisa Maroufpoor

Abstract Dispersivity is a measurable parameter in soil porous media that is used for studying the transport of contaminants to groundwater. The value of this parameter depends on various factors, including the kind of porous media (homogeneous or heterogeneous), flow velocity, initial contaminant concentration, travel distance, and sampling method. A physical model with dimensions of 0.10 m in width, 0.80 m in height, and 1.10 m in length was constructed to investigate the effects of these parameters on the dispersivity value. The stratified soil consisted of three 20-cm-thick layers containing fine-grained, medium-grained, and coarse-grained soil. Sodium chloride solutions with electrical conductivity values of 10, 14, and 19 dS/m were used as the contaminants. Flow was forced through the layered heterogeneous soils at three discharge velocities of 17.58, 22.02, and 26.18 × 10−5 m/s. The point and mixed sampling methods were used. The results indicated that the soil dispersivity values in the layered heterogeneous soils and homogeneous soil were influenced by contaminant concentration, flow velocity, and travel distance. Moreover, the dispersivity values obtained by point sampling were lower than those obtained using the mixed sampling method, and the mean dispersivity value in the layered heterogeneous soils was lower than that of the homogeneous soil.


Vestnik MGSU ◽  
2015 ◽  
pp. 110-119 ◽  
Author(s):  
Svetlana Yur’evna Shekhovtsova ◽  
Marina Alekseevna Vysotskaya

In the modern world nanotechnologies are an integral part of successful and progressive development of all the areas of activity. Materials science is not an exception. The authors studied the method of nanomodification and its influence on the performance properties of polymer-modified binder (PMB) and asphalt concrete, produced on their basis. It is established that nanomodified PMB are less susceptible to aging, which is a consequence of the processes of peptization of asphalt-resin complexes (ARC) in the structure of the modified binder and the crosslinking with the polymer matrix. It is revealed that nanotubes (SWCN or MWCN) used as a modifier, act as crosslinking agent and the inhibitor of the aging process in a PMB. The influence of nanomodified PMB on strength and deformation properties of asphalt concrete is investigated. It was found out that the use of modified binder in the asphalt concrete mixtures enhances the water resistance of asphalt concrete, heat resistance and shear-resistance.


1973 ◽  
Vol 30 (6) ◽  
pp. 379-382 ◽  
Author(s):  
V. M. Gulaev ◽  
K. I. Ryabtsev ◽  
V. S. Bakunov ◽  
D. N. Poluboyarinov ◽  
F. Ya. Borodai ◽  
...  

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