Cyclic shear response of fine-grained mine tailings

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 coppergoldzinc 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.

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Effects of confining stress, density and initial static shear stress on the cyclic shear response of fine-grained unclassified tailings

Géotechnique ◽

10.1680/jgeot.15.p.032 ◽

2016 ◽

Vol 66 (5) ◽

pp. 401-412 ◽

Cited By ~ 10

Author(s):

G. Suazo ◽

A. Fourie ◽

J. Doherty ◽

A. Hasan

Keyword(s):

Shear Stress ◽

Confining Stress ◽

Cyclic Shear ◽

Shear Response ◽

Fine Grained ◽

Unclassified Tailings ◽

Static Shear

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

Canadian Geotechnical Journal ◽

10.1139/t04-119 ◽

2005 ◽

Vol 42 (2) ◽

pp. 550-561 ◽

Cited By ~ 51

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.

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Water Content of Moist-Tamped Nonplastic Specimens for Constant-Volume Direct Simple Shear Testing

Geotechnical Testing Journal ◽

10.1520/gtj20210125 ◽

2021 ◽

Vol 45 (2) ◽

pp. 20210125

Author(s):

Jiarui Chen ◽

Scott M. Olson ◽

Soham Banerjee ◽

Mandar M. Dewoolkar ◽

Yves Dubief

Keyword(s):

Water Content ◽

Simple Shear ◽

Constant Volume ◽

Shear Testing ◽

Direct Simple Shear

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Cyclic Simple Shear Apparatus for Low-Strain Soil Tests

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198196154800102 ◽

1996 ◽

Vol 1548 (1) ◽

pp. 9-15 ◽

Cited By ~ 1

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.

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