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 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.

Cyclic shear strength of a loose glacial till

1988 ◽  
Vol 25 (2) ◽  
pp. 401-407
Author(s):  
Guy Lefebvre ◽  
Serge Malenfant
Keyword(s):  
Simple Shear ◽  
Glacial Till ◽  
Silty Sand ◽  
Triaxial Tests ◽  
Test Results ◽  
Shear Tests ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests ◽  
Cyclic Shear ◽  
Testing Procedures

The liquefaction potential of a loose glacial till is assessed by laboratory cyclic tests and by comparison with test results obtained on a clean sand, using the same testing procedures. The laboratory testing program of both soils included cyclic triaxial tests on saturated specimens and constant volume cyclic simple shear tests on dry specimens. The till and the sand exhibited very similar behaviour during cycling and mobilized nearly identical cyclic shear strengths in the triaxial as well as in the simple shear tests. The 28% fines content in the till did not make it more resistant to liquefaction than a clean sand. Key words: liquefaction, sand, silty sand, cyclic simple shear test, cyclic triaxial test.

Cyclic strength of a natural liquefiable sand stabilized with colloidal silica grout

2008 ◽  
Vol 45 (10) ◽  
pp. 1345-1355 ◽  
Author(s):  
J. A. Díaz-Rodríguez ◽  
V. M. Antonio-Izarraras ◽  
P. Bandini ◽  
J. A. López-Molina
Keyword(s):  
Cyclic Loading ◽  
Pore Pressure ◽  
Simple Shear ◽  
Colloidal Silica ◽  
Low Cost ◽  
Silty Sand ◽  
Experimental Program ◽  
Shear Tests ◽  
Liquefaction Resistance ◽  
Wide Range

This paper summarizes the experimental results of a series of cyclic simple shear tests on liquefiable silty sand with and without sample improvement with colloidal silica grout. The objective of the paper is to evaluate the effectiveness of colloidal silica grouting in reducing the liquefaction potential of natural silty sand. Colloidal silica was selected as a stabilizing material due to its low viscosity, wide range of gel times, nontoxicity, and low cost. The soil tested in this experimental program is a poorly graded sand with 11.5% of nonplastic silt from the Port of Lázaro Cárdenas, México. Colloidal silica treated and untreated sand specimens show different pore pressure response and deformation behavior under cyclic loading in simple shear tests. The results indicate that, for a given initial relative density and initial effective vertical stress, liquefiable silty sand specimens stabilized with colloidal silica grout generally exhibit significant gain in liquefaction resistance compared with untreated specimens. It was also found that the colloidal silica grout reduces considerably the rates of pore pressure generation and shear strain of the silty sand specimens subjected to cyclic loading.

Measurement of soil strength in simple shear tests

1991 ◽  
Vol 28 (2) ◽  
pp. 255-262 ◽  
Author(s):  
J. H. Atkinson ◽  
W. H. W. Lau ◽  
J. J. M. Powell
Keyword(s):  
Simple Shear ◽  
Shear Test ◽  
Triaxial Tests ◽  
Shear Stresses ◽  
Shear Tests ◽  
Laboratory Equipment ◽  
Simple Shear Test ◽  
Failure Envelopes ◽  
London Clay ◽  
Normal And Shear Stresses

During a simple shear test the axes of stress rotate and, in a conventional apparatus in which the only stresses measured are the normal and shear stresses on horizontal planes, it is not possible to define the stress state completely. As a result, the measured failure stresses may not represent the true strength of the soil. Examination of possible Mohr's circles for soils at failure in simple shear tests demonstrates that the measured strength for a given soil depends on, among other things, the ratio of the horizontal and vertical effective stresses at failure. Results of laboratory tests on Cowden Till and on blue London Clay show the differences between strengths measured in simple shear and triaxial tests. A consequence of the conventional interpretation of the simple shear test is that effective stress failure envelopes have a false cohesion intercept with friction angles smaller than those measured in triaxial tests. Key words: clays, laboratory equipment, shear strength, shear tests, triaxial tests.

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 Effect of Shear/Axial Stress Ratio on Multiaxial Non-Proportional Loading Fatigue Damage on AISI 303 Steel

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 89
Author(s):  
Vitor Anes ◽  
Luis Reis ◽  
Manuel Freitas
Keyword(s):  
Stress Ratio ◽  
Axial Stress ◽  
Experimental Program ◽  
Shear Stresses ◽  
Normal Stresses ◽  
Proportional Loading ◽  
Varied Range ◽  
Number Of Cycles ◽  
The Relationship ◽  
Cycles To Failure

In this paper, we investigate the cyclic response of AISI 303 stainless steel subjected to non-proportional loads with different amplitude ratios between shear stresses and normal stresses. Based on the experiments, a relationship between the proportional reference load and a varied range of non-proportional loads was established. To achieve this objective, an experimental program was implemented to evaluate the non-proportional parameter Y. Then, the evolution of this parameter was analyzed with the number of cycles to failure and with the ratio between shear and normal stresses, finally, the evolution of the non-proportional parameter Y was mapped by two functions. The results show that the non-proportional response of the AISI 303 can be estimated using the two functions obtained. This allows the estimation of the relationship between non-proportional and proportional stresses as a function of the number of cycles to failure together with the relationship between shear and normal stresses. The results obtained have direct application in the evaluation of accumulated damage, assessed in real-time, resulting from variable amplitude loading spectra. This is of particular interest for the evaluation of structural health monitoring of structures and mechanical components.

Failure state of a sand in simple shear

1988 ◽  
Vol 25 (2) ◽  
pp. 395-400 ◽  
Author(s):  
Muniram Budhu
Keyword(s):  
Stress State ◽  
Shear Strain ◽  
Simple Shear ◽  
Shear Stresses ◽  
Stress Concentrations ◽  
Shear Tests ◽  
Failure State ◽  
Failure Loads ◽  
Test Soil ◽  
Geotechnical Problems

The stress state in many practical geotechnical problems is analogous to simple shear strain. However, the devices available to test soil samples in simple shear strain impose nonuniform stress and strain fields. Consequently, the interpretation of results from simple shear tests is often questioned. In this article, results of tests on loose and dense Leighton Buzzard sand from two specially instrumented simple shear devices–Cambridge University's device and a Norwegian Geotechnical Institute type–are used to interpret the failure mode and the failure stress state. The data were obtained from the centre of the samples, a region removed from stress concentrations. Failure was observed to be initiated on vertical planes and occurred very soon after shear displacement was applied. However, neither these vertical planes nor the horizontal planes were the planes of maximum stress obliquity mobilized during the tests. Key words: deformation, failure, loads, sand, shear tests, simple shear, stresses.

Strain Accumulation Procedure During Staged Cyclic Loading of Carbonate Sediments

2014 ◽  
Author(s):  
Nathalie Boukpeti ◽  
Barry Lehane ◽  
J. Antonio H. Carraro
Keyword(s):  
Shear Stress ◽  
Cyclic Loading ◽  
Shear Strain ◽  
Simple Shear ◽  
Soil Strength ◽  
Carbonate Sediments ◽  
Strain Accumulation ◽  
Shear Tests ◽  
Cyclic Shear ◽  
North West

Design of offshore foundation systems requires assessment of the effects of cyclic loading on the soil strength. This paper investigates the applicability of the strain accumulation procedure, which is used to assess the effects of wave loading on the soil strength. Staged undrained cyclic simple shear tests were conducted on a carbonate sediment from the North West shelf of Australia, with varying shear stress amplitude in each stage. The shear strain mobilised at the end of the staged tests is compared with the value predicted by the strain accumulation procedure, using shear strain contours constructed from the results of single amplitude undrained cyclic simple shear tests. It was found that the strain accumulation procedure gives adequate prediction for normalised cyclic shear stress less or equal to 0.3, but largely underestimates the cyclic shear strain for normalised cyclic shear stress greater than 0.3 (the cyclic shear stress being normalised by the effective vertical stress at the end of consolidation).

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