Cyclic loading response of loose air-pluviated Fraser River sand for validation of numerical models simulating centrifuge tests

2005 ◽  
Vol 42 (2) ◽  
pp. 550-561 ◽  
Author(s):  
Dharma Wijewickreme ◽  
Somasundaram Sriskandakumar ◽  
Peter Byrne
Keyword(s):  
Cyclic Loading ◽  
Simple Shear ◽  
Mechanical Response ◽  
Shear Loading ◽  
Shear Stresses ◽  
Fraser River ◽  
River Sand ◽  
Cyclic Shear ◽  
Direct Simple Shear ◽  
Static Shear

Cyclic loading response of loose Fraser River sand was investigated, as input to numerical simulation of centrifuge physical models, using constant-volume direct simple shear tests conducted with and without initial static shear stress condition. Although the observed trends in mechanical response were similar, air-pluviated specimens were more susceptible to liquefaction under cyclic loading than their water-pluviated counterparts. Densification due to increasing confining stress (stress densification) significantly increased the cyclic resistance of loose air-pluviated sand, with strong implications for the interpretation of observations from centrifuge testing. The stress densification effect, however, was not prominent in the case of water-pluviated specimens. The differences arising from the two specimen reconstitution methods can be attributed to the differences in particle structure and highlight the importance of fabric effects in the assessment of the mechanical response of sands. The initial static shear stresses appear to reduce the cyclic shear resistance of loose air-pluviated sand in simple shear loading, in contrast to the increases in resistance reported on the basis of data from triaxial testing. Data from laboratory element tests that closely mimic the soil fabric and loading modes of the centrifuge specimens are essential for meaningful validation of numerical models.Key words: liquefaction of sands, air-pluviation, cyclic loading, direct simple shear testing, specimen preparation, fabric.

A Comparative Study of the Response of Double Shearing and Hypoplastic Models

2002 ◽  
Author(s):  
Huaning Zhu ◽  
Morteza M. Mehrabadi ◽  
Mehrdad Massoudi
Keyword(s):  
Cyclic Loading ◽  
Mechanical Response ◽  
Constitutive Relations ◽  
Constitutive Models ◽  
Shear Loading ◽  
Biaxial Compression ◽  
Finite Element Program ◽  
Cyclic Shear ◽  
Hypoplastic Model ◽  
Element Program

The principal objective of this paper is to compare the mechanical response of a double shearing model with that of a hypoplastic model under biaxial compression and under cyclic shear loading. As the origins and nature of these two models are completely different, it is interesting to compare the predictions of these two models. The constitutive relations of the double shearing and the hypoplastic models are implemented in the finite element program ABACUS/Explicit. It is found that the hypoplastic and the double shearing constitutive models both show strong capability in capturing the essential behavior of granular materials. In particular, under the condition of non-cyclic loading, the stress ratio and void ratio predictions of the double shearing and the hypoplastic models are relatively close, while under the condition of cyclic loading, the predictions of these models are quite different. It is important to note that in the double shearing model employed in this comparison the shear rates on the two slip systems are assumed to be equal. Hence, the conclusions derived in this comparison pertain only to this particular double shearing model. Similarly, the hypoplasticity model considered here is that proposed by Wu, et al. [30] and the conclusions reached here pertain only to this particular hypoplasticity model.

Cyclic shear response of fine-grained mine tailings

2005 ◽  
Vol 42 (5) ◽  
pp. 1408-1421 ◽  
Author(s):  
Dharma Wijewickreme ◽  
Maria V Sanin ◽  
Graham R Greenaway
Keyword(s):  
Shear Strength ◽  
Simple Shear ◽  
Mine Tailings ◽  
Mechanical Response ◽  
Constant Volume ◽  
Confining Stress ◽  
Cyclic Shear ◽  
Shear Response ◽  
Fine Grained ◽  
Direct Simple Shear

The mechanical response of three different types of fine-grained mine tailings is examined using data from constant-volume cyclic direct simple shear (DSS) tests. Under cyclic DSS loading, fine-grained tailings typically exhibit a cumulative decrease in effective stress along with progressive degradation of shear stiffness. The observed shear strain development due to cyclic mobility is similar in form to that of the previously observed cyclic shear response for natural silts. The cyclic resistance ratio (CRR) of laterite tailings is observed to increase with an increase in the initial effective confining stress (σ′vc). For this material, the dilative tendency due to stress densification seems to have overridden the contractive tendency due to the increase in confining stress. In contrast, the CRR of copper–gold–zinc tailings is insensitive to the initial effective confining stress, suggesting a response similar to that of normally consolidated clay. The postcyclic maximum shear strength ratio (Su-PC /σ′vc) obtained from constant-volume monotonic DSS tests is noted to increase with a decrease in the void ratio. For the fine-grained tailings considered in this study, the liquefaction susceptibility predicted using commonly used empirical criteria is not always in agreement with the liquefaction triggering determined from cyclic DSS tests.Key words: tailings, liquefaction, cyclic stress ratio, postcyclic shear strength, direct simple shear testing.

Normalized behavior of clay under irregular cyclic loading

1990 ◽  
Vol 27 (1) ◽  
pp. 29-46 ◽  
Author(s):  
Mladen Vucetic
Keyword(s):  
Cyclic Loading ◽  
Simple Shear ◽  
Shear Loading ◽  
Repeated Loading ◽  
Stress Strain ◽  
Systematic Analysis ◽  
Strain Behavior ◽  
Direct Simple Shear ◽  
Two Factors ◽  
Test Soil

A systematic analysis of the undrained stress–strain behavior of clay under irregular cyclic simple shear loading is presented. Seven specimens of an offshore clay consolidated to overconsolidation ratios of 1, 2, and 4 were subjected to different combinations of variable and nonsymmetric cyclic amplitudes using the Norwegian Geotechnical Institute (NGI) direct simple shear device. The test results show that (1) the behavior under such loads is influenced by several different factors, (2) among these factors the loading history and cyclic stiffness degradation are predominant, and (3) the irregular cyclic loading stress–strain curves can be described quite well by five rules that incorporate only these two factors. Four out of these five rules are the extensions of two original and two extended Masing rules to the behaviour of cyclically degrading clay. The fifth rule is new. The effects of the S-shaping of the stress–strain curves and the rate of loading on the applicability of the rules are also discussed. The stress–strain curves are presented in the normalized form with respect to the vertical effective consolidation stress. In this form they show quantitatively the same trends, indicating that such normalization is applicable to irregular cyclic loading. Key words: clay, earthquake loading, laboratory test, ocean soil, overconsolidation, simple shear test, soil dynamics, strain rate effect, repeated loading.

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%.

Cyclic Simple Shear Apparatus for Low-Strain Soil Tests

1996 ◽  
Vol 1548 (1) ◽  
pp. 9-15 ◽  
Author(s):  
Heather J. Miller ◽  
Pedro de Alba ◽  
Kenneth C. Baldwin
Keyword(s):  
Shear Modulus ◽  
Shear Strain ◽  
Simple Shear ◽  
Recovery Period ◽  
Triaxial Tests ◽  
Cyclic Shear ◽  
Aging Period ◽  
Direct Simple Shear ◽  
Fabric Evolution ◽  
Excess Pore Pressures

A testing system has been developed to study the behavior of saturated sand under low-level cyclic shearing strains. The system has been used to determine threshold shear strain levels for fabric destruction in sand aged for different time periods. The system includes a special soil chamber and a direct simple shear (DSS) machine. To impose very small shearing strains, the DSS machine was designed to apply and measure horizontal deformations as small as 0.0005 mm (2 × 10−5 inches). Data obtained to date support the results of previous investigators who performed triaxial tests on freshly deposited samples, indicating a threshold cyclic shear strain level of approximately 0.01 percent. At strains in excess of those levels, destruction of the sand fabric occurred, as evidenced by a reduction in shear modulus at low strain levels. Subsequent modest increases in shear modulus were observed after the specimens were allowed to recover for 24 hours and then tested again. During the recovery period, drainage valves were left open to allow for dissipation of excess pore pressures and for potential consolidation during the short aging period. The DSS system was found to work well for low strain measurements. Furthermore, since shear strains are measured directly under DSS conditions (as opposed to triaxial conditions), the DSS system shows much promise as a device for studying parameters that may influence threshold shear strain levels and fabric evolution and destruction in sands.

scholarly journals Non-coaxiality of sand under bi-directional shear loading

2018 ◽  
Vol 5 (5) ◽  
pp. 172076 ◽  
Author(s):  
Yao Li ◽  
Yunming Yang
Keyword(s):  
Shear Stress ◽  
Strain Rate ◽  
Simple Shear ◽  
Shear Test ◽  
Shear Loading ◽  
Shear Behaviour ◽  
Shear Stresses ◽  
Simple Shear Test ◽  
Principal Axes ◽  
Angle Difference

This study aims to investigate the effect of consolidation shear stress magnitude on the shear behaviour and non-coaxiality of soils. In previous drained bi-directional simple shear test on Leighton Buzzard sand, it is showed that the level of non-coaxiality, which is indicated by the angle difference between the principal axes of stresses and the corresponding principal axes of strain rate tensors, is increased by increasing angle difference between the direction of consolidation shear stress and secondary shearing. This paper further investigated the relation and includes results with higher consolidation shear stresses. Results agree with the previous relation, and further showed that increasing consolidation shear stresses decreased the level of non-coaxiality in tests with angle difference between 0° and 90°, and increased the level of non-coaxiality in tests with angle difference between 90° and 180°.

Static and cyclic stress distributions in a buckling shear panel

1969 ◽  
Vol 4 (4) ◽  
pp. 278-284 ◽  
Author(s):  
R J Frost ◽  
P P Benham
Keyword(s):  
Stress Ratio ◽  
Cyclic Stress ◽  
Shear Loading ◽  
Stress Conditions ◽  
Accurate Assessment ◽  
Stress Distributions ◽  
Cyclic Shear ◽  
Shear Panel ◽  
Assessment Of Stress ◽  
Static Shear

A panel comprising a thin, square, flat plate of clad copper-aluminium alloy to specification B.S.2L.73, bounded by substantial edge members, was subjected to a range of static shear loadings up to a shear-stress ratio of 3·0. The experimentally determined distributions of strains and stresses within the plate reveal the importance of the stresses due to bending resulting from the formation of diagonal shear buckles. Fair agreement between the results of this study and the work of other investigators was obtained. The work presented is part of an investigation into the fatigue-crack propagation behaviour and residual-strength characteristics of flat panels subjected to shear loading, hence an accurate assessment of stress conditions at least along the two diagonals was required. The strains within the plate when subjected to a range of cyclic shear loadings were determined and a relation between cyclic strains and corresponding static strains was obtained. The use of this relation leads to a simple assessment of stress conditions within the plate due to any magnitude of cyclic shear loading.

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