Initiation of static liquefaction and the role of K0 consolidation

2005 ◽  
Vol 42 (3) ◽  
pp. 892-906 ◽  
Author(s):  
A B Fourie ◽  
L Tshabalala
Keyword(s):  
Effective Stress ◽  
Triaxial Compression ◽  
Stress Path ◽  
Compression Tests ◽  
Predicting Factors ◽  
Static Liquefaction ◽  
Peak Shear Stress ◽  
Material State ◽  
Undrained Loading ◽  
Gold Tailings

The potential for static liquefaction of hydraulically placed sands and silts is now well recognised. A particular category of this type of operation, tailings disposal facilities constructed using the upstream method, has come under increased scrutiny due to the large number of failures of these structures. Although the conditions that render a particular deposit susceptible to potential liquefaction are now well known, being a combination of void ratio and mean effective stress that places the material state above its steady state value, the same cannot be said about our ability to predict the stresses at which liquefaction will be initiated. The concept of a collapse surface, derived from the locus of peak shear stress values from undrained compression tests on isotropically consolidated specimens, attempts to provide a method for predicting the onset of liquefaction. As confirmed in this paper, however, application of the collapse surface concept to actual tailings dam facilities results in factors of safety based on an effective stress approach that are significantly less than unity for facilities that have not failed. On the other hand, shear strength values derived from ultimate state conditions are unconservative, predicting factors of safety significantly in excess of unity for facilities that have failed. A comparison of monotonic undrained triaxial compression tests on both isotropically- and K0-consolidated specimens of gold tailings suggests that the resolution to this dilemma lies in the recognition that a kinematic yield surface, which is a function of the consolidation stress path followed, develops in stress space. The collapse surface derived from undrained loading of K0-consolidated loose specimens is shown to provide a greatly improved capacity for predicting the onset of liquefaction under undrained loading conditions.Key words: static liquefaction, tailings, collapse surface, anisotropic.

Undrained anisotropy of Hostun RF loose sand: new experimental investigations

2006 ◽  
Vol 43 (11) ◽  
pp. 1195-1212 ◽  
Author(s):  
Zeina Finge ◽  
Thiep Doanh ◽  
Phillippe Dubujet
Keyword(s):  
Effective Stress ◽  
Stress Ratio ◽  
Triaxial Compression ◽  
Stress Path ◽  
Experimental Investigations ◽  
Loose Sand ◽  
Induced Anisotropy ◽  
Static Liquefaction ◽  
Stress States ◽  
Effective Stress Ratio

The undrained behaviour of loose and overconsolidated Hostun RF sand in triaxial compression and extension tests is described. The samples are isotropically or anisotropically overconsolidated along several constant effective stress ratio paths with various overconsolidation ratios (OCR), up to 24. To minimize the effect of variation of density on the observed undrained behaviour, all tested samples are required to have a nearly identical void ratio before the final monotonic undrained shearing. Isotropically overconsolidated and normally consolidated samples exhibit the same phenomenon of partial static liquefaction, but anisotropically overconsolidated specimens reveal a completely different undrained behaviour. A common pseudoelastic response is observed for a given overconsolidation history. This response is induced by recent stress history in terms of effective stress paths, independent of the OCR during overconsolidation. The initial gradient of the effective stress paths seems to depend solely on the direction of the previous linear stress path history. This paper offers a comprehensive understanding of the mechanism of the induced anisotropy of loose sand created by simple linear stress paths from three different initial stress states in the classical triaxial plane. The pseudoelastic response can be adequately modelled by a simple hyperelastic component of the elastoplastic framework.Key words: induced anisotropy, overconsolidation, instability, laboratory undrained tests, sand, hyperelasticity.

scholarly journals The influence of particle breakage on stress-dilatancy relationship for granular soils

2019 ◽  
Vol 92 ◽  
pp. 09004 ◽  
Author(s):  
Zenon Szypcio
Keyword(s):  
Internal Energy ◽  
Stress Level ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
Stress Path ◽  
State Theory ◽  
Particle Breakage ◽  
Compression Tests ◽  
Particle Crushing ◽  
Soil Gradation

The influence of particle breakage on soil behaviour is important from theoretical and practical perspectives. Particle breakage changes the internal energy in two ways. First, internal energy is consumed for particle crushing and second, the internal energy changes because of additional volumetric strain caused by particle crushing. These two effects may be quantified by use of Frictional State Theory. The analysed drained triaxial compression tests of Toyoura sand, gravel and Dog's Bay sand at different stress level and stress path revealed that the effect of particle breakage is a function of soil gradation, strength of soil grains, stress level and stress path.

Anisotropic shear strength of a residual soil of sandstone

2008 ◽  
Vol 45 (3) ◽  
pp. 367-376 ◽  
Author(s):  
Adriano Virgilio Damiani Bica ◽  
Luiz Antônio Bressani ◽  
Diego Vendramin ◽  
Flávia Burmeister Martins ◽  
Pedro Miguel Vaz Ferreira ◽  
...  
Keyword(s):  
Shear Strength ◽  
Effective Stress ◽  
Yield Surface ◽  
Triaxial Compression ◽  
Strength Properties ◽  
Triaxial Tests ◽  
Residual Soil ◽  
Compression Tests ◽  
Soil Stiffness ◽  
Particle Bonding

This paper discusses results of laboratory tests carried out with a residual soil originated from the weathering of eolian sandstone from southern Brazil. Parent rock features, like microfabric and particle bonding, are remarkably well preserved within this residual soil. Stiffness and shear strength properties were evaluated with consolidated drained (CID) and consolidated undrained (CIU) triaxial compression tests. Undisturbed specimens were tested with two different orientations between the specimen axis and bedding surfaces (i.e., parallel (δ = 0°) or perpendicular (δ = 90°)) to investigate the effect of anisotropy. When CID triaxial tests were performed with δ = 0°, the yield surface associated with the structure was much larger than when tests were performed with δ = 90°. Coincidently, CIU tests with δ = 0° showed peak shear strengths much greater than for δ = 90° at comparable test conditions. Once the peak shear strength was surpassed, CIU tests followed collapse-type effective stress paths not shown by corresponding tests with remolded specimens. A near coincidence was observed between the yield surface determined with CID tests and the envelope of collapse-type effective stress paths for δ = 0° and δ = 90°.

Defining an appropriate steady state line for Merriespruit gold tailings

2001 ◽  
Vol 38 (4) ◽  
pp. 695-706 ◽  
Author(s):  
A B Fourie ◽  
G Papageorgiou
Keyword(s):  
South Africa ◽  
Steady State ◽  
Companion Paper ◽  
Tailings Dam ◽  
Test Results ◽  
Failure Investigation ◽  
Static Liquefaction ◽  
Flow Failure ◽  
Undrained Loading ◽  
Gold Tailings

Failure of the Merriespruit gold tailings dam in 1994 in South Africa was unusual in that never before had a gold tailings dam in South Africa failed in such a catastrophic fashion. Conventional thinking was that gold tailings would always exhibit dilative characteristics upon loading, primarily because of the method of deposition which allows significant consolidation to occur due to sun-drying. This paper demonstrates that the concept of a steady state line, which separates dilative from contractive behaviour upon undrained loading, is applicable to Merriespruit tailings. Four particle-size distributions of Merriespruit tailings were tested to determine the influence of the percent finer than 75 µm on the position of the steady state line. The tailings with the greater percentage of fines gave a steady state line that plotted above all the others, which translated to the requirement that a greater relative density was necessary to produce noncontractive behaviour than for the low-fines tailings samples. The difficulty of defining a unique steady state line for a particular tailings, due to errors in measurement of initial sizes, is illustrated and it is recommended that error bands be assigned to any steady state line. In a companion paper, evidence from the post-failure investigation is combined with the test results in this paper to explore the likelihood of static liquefaction as the cause of the Merriespruit flow failure.Key words: static liquefaction, tailings, steady state, flow failure.

scholarly journals Undrained monotonic triaxial loading behaviors of a type of iron ore fines

2018 ◽  
Vol 55 (9) ◽  
pp. 1349-1357 ◽  
Author(s):  
Hailong Wang ◽  
Junichi Koseki ◽  
Fei Cai ◽  
Tomoyoshi Nishimura
Keyword(s):  
Iron Ore ◽  
Initial Conditions ◽  
Triaxial Compression ◽  
Axial Loading ◽  
Sandy Soils ◽  
Peak Stress ◽  
Confining Pressure ◽  
Compression Tests ◽  
Static Liquefaction ◽  
Iron Ore Fines

Concerning the static liquefaction properties of an industrial cargo, i.e., iron ore fines (IOF), undrained monotonic behaviors of a type of IOF are revealed through conducting triaxial compression tests. It is found that IOF exhibit some similar behaviors as those of common sandy soils, while some very unusual behaviors are also observed. All IOF specimens with compaction degree of 84%–95% and confining pressure of 50–200 kPa exhibit dilative behavior from the beginning of axial loading until the deviator stresses reach their peaks (qpk). Then the dilative behavior transforms to a contractive behavior, and the contractive behavior continues until reaching the residual stress without observation of phase transformation and quasi steady state. These behaviors are not usually observed for common sandy soils based on extensive previous works. More studies may be necessary as these unusual behaviors imply that flow failure, similar to the undrained monotonic behavior of very loose sand, may be triggered regardless of the density of IOF. In addition, this study also establishes the relationships of IOF between its initial conditions, peak stress conditions, and residual conditions by employing classical knowledges developed for sandy soils.

Stress path effects on the strength behaviour of a layered soil

1980 ◽  
Vol 17 (4) ◽  
pp. 603-607 ◽  
Author(s):  
M. Krishna Murthy ◽  
T. S. Nagaraj ◽  
A. Sridharan
Keyword(s):  
Experimental Investigation ◽  
Effective Stress ◽  
Volume Change ◽  
Stress Path ◽  
Layered Soil ◽  
Shear Behaviour ◽  
Compression Tests ◽  
Stress Strain ◽  
Strain Behaviour ◽  
Stress Parameters

An experimental investigation dealing with the influence of stress path on the shear behaviour of a layered soil prepared in the laboratory is described. Specimens trimmed in vertical and horizontal directions have been sheared under three different stress paths in compression and extension tests. Either in compression or extension, the stress–strain behaviour of the specimens with both orientations was apparently the same, although the volume change behaviour was different. The effective stress parameters C′ and [Formula: see text]′ were found to be unique and independent of the stress path and two principal orientations. However, the values of [Formula: see text]′ in extension tests were 6–7° higher than those in compression tests.

Collapse of dry sand

1994 ◽  
Vol 31 (6) ◽  
pp. 1008-1014 ◽  
Author(s):  
Peter Skopek ◽  
N.R. Morgenstern ◽  
P.K. Robertson ◽  
D.C. Sego
Keyword(s):  
Stress Path ◽  
Shear Stresses ◽  
Cyclic Shear ◽  
Pore Pressures ◽  
Static Liquefaction ◽  
Triaxial Cell ◽  
Flow Slides ◽  
Dry Sand ◽  
Stress States ◽  
Undrained Loading

Loose cohesionless saturated materials have proved responsible for a number of serious or catastrophic flow slides. Liquefaction failures with no obvious triggering mechanism have also been recorded. This phenomenon of sudden liquefaction without a presence of cyclic shear stresses is often referred to as spontaneous or static liquefaction. Results from previously published studies suggest that liquefaction is triggered not by the undrained loading and generation of pore pressures but by the collapse of the metastàble sand structure, which in turn generates the driving pore pressures in a saturated material. Hence, the collapse is a characteristic response of a material to certain stress states rather than a result of some enforced undrained loading. This theory is evaluated on very loose dry Ottawa sand. It is shown that the very loose dry sand when subjected to a constant deviatoric stress path significantly changes its behavior at a certain discreet stress state, increases compressibility, and becomes increasingly unstable. This results in collapse – vigorous contraction of the specimen. This structural collapse appears to be equivalent to the pore-pressure generation in collapsing, very loose saturated sand. Key words : dry sand, collapse, liquefaction, stress path, triaxial cell.

scholarly journals Static liquefaction and effective stress path response of Kutch soils

2019 ◽  
Vol 59 (6) ◽  
pp. 2036-2055 ◽  
Author(s):  
Majid Hussain ◽  
Ajanta Sachan
Keyword(s):  
Effective Stress ◽  
Stress Path ◽  
Static Liquefaction ◽  
Effective Stress Path

Unloading Triaxial Experimental Study on Stress Path of Excavated Soil Slope

2011 ◽  
Vol 243-249 ◽  
pp. 2797-2801 ◽  
Author(s):  
Yan Gang Zhang ◽  
Kun Yong Zhang ◽  
Wang Lin Li ◽  
Qiao Zhen Shi
Keyword(s):  
Principal Stress ◽  
Triaxial Compression ◽  
Constitutive Models ◽  
Confining Pressure ◽  
Stress Path ◽  
Soil Mass ◽  
Soil Slope ◽  
Compression Tests ◽  
Excavation Process ◽  
Major Principal Stress

The current research was implemented to study the practical unloading stress path that the slope mass experienced during the excavation process, which is very important in the stress and strain numerical analysis. Series of unloading tests were carried out under different confining pressure. During the test process, the minor principal stress was kept decreasing, while the major principal stress was kept unchanged to simulate the stress path in some locations of the soil slope, such as at the top of the slope. The corresponding conventional triaxial compression tests were also carried out as comparison. It is shown that there are many differences between the unloading and loading tests. Through analyzing, the tests results could be applied in the development of unloading constitutive models of excavation soil mass. Also, such unloading tests data are valuable in calibration and verification of the current existing popularly used models.

Viscous behaviour of St-Roch-de-l'Achigan clay, Quebec

2004 ◽  
Vol 41 (1) ◽  
pp. 25-38 ◽  
Author(s):  
Maria Esther Soares Marques ◽  
Serge Leroueil ◽  
Márcio de Souza Soares de Almeida
Keyword(s):  
Strain Rate ◽  
Effective Stress ◽  
Laboratory Tests ◽  
Triaxial Compression ◽  
Limit State ◽  
Compression Tests ◽  
Cone Penetration ◽  
Cone Penetration Tests ◽  
Oedometer Tests ◽  
Viscous Behaviour

This paper describes the viscous behaviour of St-Roch-de-l'Achigan clay, a Champlain Sea clay from Quebec, Canada. The general geotechnical profile of the soil deposit was first established with static cone penetration tests, vane tests, and some laboratory tests performed at different depths. For the study of the viscous behaviour of the clay, a special laboratory test program was established for specimens taken at depths from 4.8 to 5.8 m. This program included special incremental loading oedometer tests, constant rate of strain (CRS) oedometer tests performed at different strain rates, isotropic and anisotropic triaxial compression tests, and undrained shear tests. All these tests were performed under a constant temperature, varying from 10 to 50 °C. The test results show that the vertical yield stresses and the entire limit state curve depend on strain rate and temperature. The critical state line is also temperature dependent in the void ratio (e) – log principal effective stress (p′) diagram but not in the deviator stress (q) – principal effective stress (p′) diagram. The results also show that microstructuring may develop when the temperature is high or the strain rate small.Key words: viscosity, strain rate, temperature, laboratory tests.

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