scholarly journals Numerical Modeling of the Degradation of the Normal Stress Under Large Number of Shearcycles

2021 ◽  
Vol 31 (3) ◽  
pp. 118-133
Author(s):  
Assia Bellayoune ◽  
Salah Messast ◽  
Marc Boulon
Keyword(s):  
Numerical Modeling ◽  
Normal Stress ◽  
Horizontal Stress ◽  
Cyclic Stress ◽  
Simple Expression ◽  
Shear Tests ◽  
Cyclic Shear ◽  
Explicit Formulation ◽  
Number Of Cycles

Abstract The evaluation of friction is an important element in the verification of stability and the determination of the bearing capacity of piles. In the case of cyclic stress, the soil-pile interface has a relaxation which corresponds to a fall in the horizontal stress which represents the normal stress at the lateral surface of the pile. This paper presents an explicit formulation to express the degradation of the normal stress after a large number of shear cycles as a function of cyclic parameters. In this study we are interested in the exploitation of the cyclic shear tests carried out by Pra-ai [1] with imposed normal rigidity (CNS) in order to demonstrate the phenomenon of falling of the normal stress. The approach presented in this paper consists in proposing a simple expression for estimating the degradation of normal stress as a function of cyclic shear parameters after a large number of cycles. The validation of this approach is verified by the application of this formulation to a real case where the comparison of the simulations made by this approach with those recorded on site shows the good adaptation of this approach to this type of problems.

scholarly journals Cyclic and Permanent Shear Strains of a Soft Cohesive Soil Subjected to Combined Static and Cyclic Loading

2020 ◽  
Vol 10 (23) ◽  
pp. 8433
Author(s):  
Hernán Patiño ◽  
Rubén Galindo ◽  
Claudio Olalla Marañón
Keyword(s):  
Simple Shear ◽  
Cohesive Soil ◽  
Mediterranean Coast ◽  
Vertical Stress ◽  
Experimental Program ◽  
Shear Stresses ◽  
Shear Tests ◽  
Cyclic Shear ◽  
Shear Strains ◽  
Number Of Cycles

This paper refers to cyclic shear strains (γc) and permanent shear strains (γp) of a soft cohesive soil, when both monotonic shear stresses (τo) and cyclic shear stresses (τc) are applied. The research is backed by an extensive experimental program with 139 cyclic simple shear tests that included identification and classification tests. These cyclic simple shear tests were conducted under different levels of stresses, τo, before the cyclic phase. Laboratory tests were carried out on undisturbed samples from the Port of Barcelona, located in Spain on the Mediterranean coast, and characterized by a monotonic strength (τmax) approximately equal to 30% of the initial effective vertical stress (σ′ov). The samples were taken at depths between 29 and 52 m and correspond to an initial effective vertical stress between 277 and 413 kPa, respectively. In general, the results indicate that: (a) the combination of τo and τc controls the generation of γc and γp, (b) it is not always true that when τo/σ′ov + τc/σ′ov ≈ τmax/σ′ov, the soil reaches failure cyclically, and (c) empirical relations useful for design can be established between γc, γp, and the number of cycles (N), for different relationships varying (τo/σ′ov) between 0% and 25%.

scholarly journals Pore water pressure responses of saturated sand and clay under undrained cyclic shearing

2021 ◽  
Author(s):  
An ◽  
Hiroshi ◽  
Nhan ◽  
Nhan ◽  
Tien ◽  
...  
Keyword(s):  
Shear Strain ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Silty Clay ◽  
Shear Tests ◽  
Sand Liquefaction ◽  
Cyclic Shear ◽  
Wide Range ◽  
Number Of Cycles

In this study, changes in the pore water pressure were observed for saturated specimens of a loose fined-grain sand (Nam O sand) and a soft silty clay (Hue clay) subjected to undrained cyclic shearing with different testing conditions. The cyclic shear tests were run for relatively wide range of shear strain amplitude (g = 0.05%-2%), different cycle numbers (n = 10, 50, 150 and 200) and various shear directions (uni-direction and two-direction with phase difference of q = 0o, 45o and 90o). It is indicated from the experimental results that under the same cyclic shearing condition, the pore water pressure accumulation in Hue clay is at a slower rate, suggesting a higher cyclic shear resistance of Hue clay than that of Nam O sand. Liquefaction is reached easily in nominally 50% relative density specimens of Nam O sand when g ³ 0.4%, meanwhile soft specimen of Hue clay is not liquefied regardless of the cyclic shearing conditions used in this study. The threshold number of cycles for the pore water pressure generation generally decreases with g meanwhile, the threshold cumulative shear strain for such a property mostly approaches 0.1%. In addition, by using this new strain path parameter, it becomes more advantageous when evaluating the pore water pressure accumulation in Nam O sand and Hue clay subjected to undrained uni-directional and two-directional cyclic shears.

scholarly journals A parametric study on cyclic strength of coastal sand of Digha in West Bengal, India

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Pinak Ray ◽  
Ramendu Bikas Sahu
Keyword(s):  
West Bengal ◽  
Confining Pressure ◽  
Cyclic Stress ◽  
Cyclic Strength ◽  
Triaxial Tests ◽  
Cyclic Stress Ratio ◽  
Confining Pressures ◽  
Coastal Sand ◽  
Number Of Cycles

AbstractStress controlled cyclic triaxial tests have been carried out on coastal sand of Digha, West Bengal, India at different frequencies, confining pressures, relative densities and number of loading cycles for determination of influence of these parameters on cyclic strength (expressed in terms of cyclic stress ratio) and initial liquefaction of Digha sand. The test results provide evidence that increasing density of sand increases liquefaction potential, though it has been found that increase in effective confining pressure reduces cyclic strength of sand. Cyclic strength of sand decreases with increase of number of loading cycles at a specific density and a particular confining pressure. It has been observed that frequency of loading cycles does have any significant influence on the number of cycles for initial liquefaction of Digha sand. An empirical correlation has been developed on cyclic strength of sand based on these parameters and it has been found that this correlation fits quite well with the observed experimental results.

scholarly journals CYCLIC STRESS ANALYSIS OF POLYESTER, ARAMID, POLYETHYLENE AND LIQUID CRYSTAL POLYMER YARNS

2016 ◽  
Vol 56 (5) ◽  
pp. 402-408 ◽  
Author(s):  
Felipe Vannucchi de Camargo ◽  
Carlos Eduardo Marcos Guilherme ◽  
Cristiano Fragassa ◽  
Ana Pavlovic
Keyword(s):  
Liquid Crystal ◽  
Fatigue Behavior ◽  
Cyclic Stress ◽  
Liquid Crystal Polymer ◽  
Oil Platforms ◽  
Crystal Polymer ◽  
Offshore Oil Platforms ◽  
Number Of Cycles ◽  
Offshore Oil

Mooring ropes used in offshore oil platforms are exposed to a set of extreme environmental conditions that can be crucial to their behaviour in service. Considering the elevated mechanical demands on these ropes imposed by both the undersea environment and the station keeping of the vessel, this paper is focused on the experimental determination of the yarns fatigue behavior. In order to be able to foresee and compare their general wear rate, a diagram that correlates the force to which the specimens are submitted to the number of cycles for failure for each material is achieved. The analyzed fibers are Polyester, Aramid, Polyethylne and Liquid Crystal Polymer (henceforth quoted as PET, AR, PE and LCP, respectively), and this work followed a pattern composed by a fixed test frequency and an established maximum stress for the diagrams.

Effects of T5 and T6 Heat Treatments Applied to Rheocast A356 Parts for Automotive Applications

2008 ◽  
Vol 141-143 ◽  
pp. 237-242 ◽  
Author(s):  
Mario Rosso ◽  
Ildiko Peter ◽  
R. Villa
Keyword(s):  
Fatigue Behaviour ◽  
Cyclic Stress ◽  
Industrial Applications ◽  
Fatigue Tests ◽  
Controlled Cooling ◽  
Test Analysis ◽  
Heat Treated ◽  
Mechanical Performances ◽  
Semi Solid ◽  
Number Of Cycles

The correlation between the evaluation of the mechanical and of the fatigue behaviour of the rheocast, T5 and T6 heat treated SSM A356 aluminium alloy with respect to the microstructures of the component has been investigated. The study has been carried out on a suspension arm injected in a rheocasting 800 tons plant in Stampal S.p.A. The new rheocasting is a process that allows obtaining the alloys in a semisolid state directly from the liquid state, by controlled cooling of the molten alloys. The resulting microstructures are very fine, free from defects and homogeneous: these characteristics improve the mechanical properties of the alloys and specially the response to cyclic stress, an important issue for a suspension component. After a preliminary tensile test analysis, axial high frequency fatigue tests have been carried out at room temperature on specimen cut out from the suspension arm to determine the Wöhler curve and the number of cycles to failure. The results of this work allow a comparison of the effects of heat treatment process, T5 or T6, on Semi-Solid components for industrial applications in the automotive field. On the basis of these analysis the correlation between microstructure and mechanical performances can be established.

scholarly journals Modern rheology and electric induction: multivalued index of refraction, splitting of eigenvalues and fatigue

1996 ◽  
Vol 39 (5) ◽  
Author(s):  
M. Caputo
Keyword(s):  
Constitutive Equations ◽  
Fractional Derivatives ◽  
Cyclic Stress ◽  
Index Of Refraction ◽  
Stress And Strain ◽  
Trans Form ◽  
Dielectric Media ◽  
Electric Induction ◽  
Frequency Domains ◽  
Number Of Cycles

The modern constitutive equations of the rheology of analeptic media and of the polarization in dielectric media are discussed in the time and frequency domains. It is seen that the most appropriate form of the constitutive equations of these media is based on the convolution of the stress and strain, and of the electric field and induction respectively, with appropriate functions representing the memory of the medium to previous stress or induction. The most successful memory forma]ism in representing the observed phenomena is that of the derivative of fractional order which allows a variety of problems to be solved by means of the Laplace Trans- form. The consequent index of refraction, generally, is a set valued function which implies that a monochromatic wave generated in the medium is split into a set of waves with the same frequency but different wavelength which interfere and have a quasi periodically varying amplitude. The eigenfunctions of these media, associated to the ordinarily used principal values of the index of retraction, are split and so are the tree modes. The fatigue of anelastic media is studied using the new constitutive equations containing fractional derivatives; a phenomenological method is introduced to compute the number of cycles which gives fatigue for a strain or stress with given amplitude and frequency. The number of cycles which may cause fatigue is proportional to the amplitude and frequency of the applied strain or stress, or inversely proportional to the rate of stress or strain. A criterion is also established to see whether an applied cyclic stress or strain may cause fatigue. This criterion is tested with experimental data on steel and rocks verifying that, in general, it is consistent with the data although thc data are not always in the linear range. It is tentatively seen that fatigue docs not seem one of the causes of the release of the elastic energy stored in the Earth.

scholarly journals Frictional properties between geocells filled with granular material

2021 ◽  
Vol 20 (2) ◽  
pp. 332-345
Author(s):  
Gökhan Altay ◽  
◽  
Cafer Kayadelen ◽  
Taha Taskiran ◽  
Baki Bagriacik ◽  
...  
Keyword(s):  
Granular Material ◽  
Normal Stress ◽  
Granular Materials ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
Frictional Properties ◽  
Geotechnical Structures ◽  
Series Of Experiments ◽  
Restricted Volume

The parameters concerning the interaction between geocell and granular materials is required for the design of many geotechnical structures. With this in mind, a series of experiments using simple direct shear tests are conducted in order to understand the frictional properties between geocells filled with granular materials. The 54 test samples are prepared by filling the geocell with granular materials having three different gradations. These samples are tested at three different relative densities under three different normal stress levels. As a result, it was observed that interface resistance between the geocells filled with granular material is found to be generally greater than in the samples without geocells. Additionally, these samples with geocells are found to be stiffer; this is due to the fact that the samples with geocell gained more cohesion because geocells confined the grains within a restricted volume.

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