Properties of Mine Tailings for Static Liquefaction Assessment

2021 ◽  
Author(s):  
Jorge Macedo ◽  
Luis Vergaray
Keyword(s):  
Mine Tailings ◽  
Mechanical Response ◽  
Fine Particles ◽  
Soil Mechanics ◽  
Small Strain ◽  
Excess Pore Pressure ◽  
Triaxial Tests ◽  
Bender Element ◽  
Static Liquefaction ◽  
Stress Ratios

Static liquefaction has been associated with numerous recent failures of tailings storage facilities (TSFs) around the world (e.g., the 2019 Brumadinho failure). These failures lead to devastating consequences for the environment and civil infrastructure, as well as the loss of human lives. In this study, we present trends for the mechanical response of mine tailings considering a) triaxial tests, b) bender element tests, and c) consolidation tests on 53 mine tailings materials (including recent case histories). These materials have a broad range of states, particle size distributions, and compressibility. The trends are evaluated in the context of static liquefaction using critical state soil mechanics concepts, focusing on the variation of the shear strength (residual and peak), state and brittleness soil indexes, excess pore pressure indexes, instability stress ratios, and dilatancy. In particular, we highlight that mine tailings mechanical properties reflect both the properties of the particles themselves and the relative proportions of different particle sizes. For instance, the observed trends suggest that particle gradation influences the small strain stiffness and dilatancy; the proportion of voids to the size of fine particles influences strength, and particle shape affects dilatancy. Finally, we propose static liquefaction screening indexes based on the observed trends.

scholarly journals Small-strain behaviour and crushability of Ballyconnelly carbonate sand under monotonic and cyclic loading

2018 ◽  
Vol 55 (7) ◽  
pp. 979-987 ◽  
Author(s):  
S. Nanda ◽  
V. Sivakumar ◽  
S. Donohue ◽  
S. Graham
Keyword(s):  
Cyclic Loading ◽  
Large Scale ◽  
Sea Water ◽  
High Stress ◽  
Small Strain ◽  
Offshore Structures ◽  
Particle Breakage ◽  
Triaxial Tests ◽  
Bender Element ◽  
Carbonate Sand

In various parts of the globe, carbonate sands are found at shallow sea water depth. These types of sands are very susceptible to large-scale particle breakage. Offshore structures like wind turbines and sea defences are constructed on these types of soils. From a design perspective, it is essential to assess the extent of particle breakage and the subsequent change in soil properties that occur under working load conditions. This paper presents the data obtained from a number of drained monotonic and cyclic triaxial tests on crushable carbonate sand (“Ballyconnelly sand”) in conjunction with small-strain shear stiffness (Gmax) measurements using the bender element technique. The soils were allowed to shear under three different loading patterns to understand the factors influencing the breakage of particles. The degree of crushing was quantified and analysed based on the total energy input. It was observed that, apart from applied stress, the total strain accumulation governs the amount of particle breakage. It was observed that Gmax increased significantly under high stress ratio. Gmax also increased noticeably during resting periods without any change in loading conditions as a result of creep, and subsequently during cyclic loading although at a reduced rate.

scholarly journals Instability of Compacted Residual Soil

Geosciences ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 403
Author(s):  
Sainulabdeen Mohamed Junaideen ◽  
Leslie George Tham ◽  
Chack Fan Lee
Keyword(s):  
Steady State ◽  
State Parameter ◽  
Triaxial Tests ◽  
Residual Soil ◽  
Test Results ◽  
Residual Soils ◽  
Constant Shear ◽  
Static Liquefaction ◽  
Constant Shear Stress ◽  
Stress Ratios

Static liquefaction of loose sands has been observed to initiate at stress ratios far less than the steady-state stress ratio. Different collapse surface concepts largely based on undrained triaxial test results have been proposed in the literature to explain the above instability phenomenon of loose sands. Studies of the instability behavior of fill material derived from residual soils remain limited. The present study investigated the instability behavior of a compacted residual soil using the conventional undrained triaxial tests and specially equipped constant shear triaxial tests. The test results were characterized in the p’: q: v space using the current state parameter with respect to the steady-state line for the residual soil. A modified collapse surface that has gradients varying with p’ and v was proposed for the loose residual soil to represent the instability states of undrained loading. Under constant shear stress conditions, the soil can mobilize stress ratios higher than those defined by the modified collapse surface. An instability surface was therefore presented for the instability states reached in static loading. Further, an alternative method of deducing the instability surface from the undrained stress paths was introduced.

Influences of initial anisotropy and principal stress rotation on the undrained monotonic behavior of a loose silica sand

2021 ◽  
Author(s):  
Kazem Fakharian ◽  
Farzad Kaviani-Hamedani ◽  
S M Reza Imam
Keyword(s):  
Phase Transformation ◽  
Critical State ◽  
Soil Mechanics ◽  
Triaxial Compression ◽  
Silica Sand ◽  
Bender Element ◽  
Cyclic Shear ◽  
Stress Rotation ◽  
Initial Anisotropy ◽  
Stress Ratios

Triaxial compression and extension tests have been conducted under different initial anisotropy conditions to investigate the undrained response of a crushed silica sand. The loose to medium specimens were prepared using the moist tamping method. Five stress paths with different stress ratios (q/p^') were employed to prepare anisotropically consolidated specimens. Several specimens were consolidated under a specific condition in which a stress rotation occurred under undrained monotonic shearing similar to a reversed cyclic shear stress loading during an earthquake. The effects of initial induced anisotropy at consolidation on the onset of liquefaction, phase transformation, and critical state are investigated within the framework of Anisotropic Critical State Soil Mechanics (ACSSM). In addition, fabric evolution during shearing towards the critical state is evaluated using bidirectional bender element tests. The results illustrate the fact that there is a unique anisotropic critical state representing anisotropic fabric, irrespective of initial anisotropy, and the states of stress. Similar to the critical state line, the phase transformation line has the same loci for different initial anisotropies.

Experimental Study on Elastic Stiffness of Kaolinite Clay

2013 ◽  
Vol 813 ◽  
pp. 395-398
Author(s):  
Keeratikan Piriyakul
Keyword(s):  
Shear Modulus ◽  
Local Strain ◽  
Small Strain ◽  
Elastic Response ◽  
Triaxial Tests ◽  
Clay Sample ◽  
Bender Element ◽  
Kaolinite Clay ◽  
Strain Measurements ◽  
Elastic Shear

This paper presents a study on the elastic shear modulus of Kaolinite clay at very small strains under isotropic stress from triaxial tests. The Kaolinite clay sample is subjected to an isotropic stress of 100, 200 and 400 kPa. In this very small strain domain where strain is less than 10-3 %, the behaviour of clay soil shows an elastic response. In conventional triaxial test, an initial shear modulus, G0, can be measured using an external strain measurement device. Nevertheless, there is an advantage to mount local strain sensors directly on a clay sample in order to obtain more accurate measurement of G0. Also the G0 can be measured by bender elements through propagation of an elastic shear wave. Therefore in this research G0 can be obtained by external, local strain measurements and bender element tests. These results of G0 in the very small strain region are compared and show that there is a good agreement between the results from local strain measurements and bender element tests.

scholarly journals Numerical Investigation to the Effect of Suction-Induced Seepage on the Settlement in the Underwater Vacuum Preloading with Prefabricated Vertical Drains

2021 ◽  
Vol 9 (8) ◽  
pp. 797
Author(s):  
Shu Lin ◽  
Dengfeng Fu ◽  
Zefeng Zhou ◽  
Yue Yan ◽  
Shuwang Yan
Keyword(s):  
Practical Implication ◽  
Soil Surface ◽  
Small Strain ◽  
Seepage Flow ◽  
Excess Pore Pressure ◽  
Combined Effects ◽  
Vacuum Preloading ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
The Difference

Vacuum preloading combined with prefabricated vertical drains (PVDs) has the potential to improve the soft sediments under water, however, its development is partly limited by the unclear understanding of the mechanism. This paper aims to extend the comprehension of the influential mechanism of overlapping water in the scenario of underwater vacuum preloading with PVDs. The systematic investigations were conducted by small strain finite element drained analyses, with the separated analysis schemes considering suction-induced consolidation, seepage and their combination. The development of settlement in the improved soil region and the evolution of seepage flow from the overlapping water through the non-improved soil region into improved zone are examined in terms of the build-up of excess pore pressure. Based on the results of numerical analyses, a theoretical approach was set out. It was capable to estimate the time-dependent non-uniform settlement along the improved soil surface in response to the combined effects of suction-induced consolidation and seepage. The difference of underwater and onshore vacuum preloading with PVDs is discussed with some practical implication and suggestion provided.

scholarly journals Research of the Behavior of Clay Materials with Double Porosity

2021 ◽  
Vol 13 (6) ◽  
pp. 3219
Author(s):  
Hynek Lahuta ◽  
Luis Andrade Pais
Keyword(s):  
Double Porosity ◽  
Strength Properties ◽  
Triaxial Tests ◽  
Building Structures ◽  
Foundation Soil ◽  
Problematic Use ◽  
The North ◽  
Static Liquefaction ◽  
Confinement Stress ◽  
Clay Materials

This contribution presents results from a series of compression and undrained triaxial tests to study the mechanical behavior of dump clay from the north of Bohemia. The use of these materials as a foundation for construction can’t be achieved without the adoption of some precautions. This comes from embankment, formed by digging the ground (altered claystone), up to the level of coal mining which is in a sub horizontal stratigraphic layer. A potential static liquefaction behavior was observed in undrained tests for high confinement stress. A structural collapse was noticed with the results obtained in the triaxial test. This collapse is characterized by an unexpected large decrease in deviator and mean effective stress. The soils formed have strength properties that are potentially dangerous. These concepts can improve the use of these kinds of soils in geotechnical engineering work. It continues and expands the results obtained in previous research, especially the future problematic use of these materials as the foundation soil for line or building structures.

Effects of fines on liquefaction behaviour in well-graded materials

2017 ◽  
Vol 54 (10) ◽  
pp. 1460-1471 ◽  
Author(s):  
Katherine A. Kwa ◽  
David W. Airey
Keyword(s):  
Critical State ◽  
Soil Mechanics ◽  
State Parameter ◽  
Triaxial Tests ◽  
Particle Sizes ◽  
Graded Materials ◽  
Fines Content ◽  
Cyclic Resistance ◽  
Wide Range ◽  
Soil Behaviour

This study uses a critical state soil mechanics perspective to understand the mechanics behind the liquefaction of metallic ores during transport by ship. These metallic ores are transported at relatively low densities and have variable gradings containing a wide range of particle sizes and fines contents. The effect of the fines content on the location of the critical state line (CSL) and the cyclic liquefaction behaviour of well-graded materials was investigated by performing saturated, standard drained and undrained monotonic and compression-only cyclic triaxial tests. Samples were prepared at four different gradings containing particle sizes from 9.5 mm to 2 μm with fines (<75 μm) contents of 18%, 28%, 40%, and 60%. In the e versus log[Formula: see text] plane, where e is void ratio and [Formula: see text] is mean effective stress, the CSLs shifted upwards approximately parallel to one another as the fines content was increased. Transitional soil behaviour was observed in samples containing 28%, 40%, and 60% fines. A sample’s cyclic resistance to liquefaction depended on a combination of its density and state parameter, which were both related to the fines content. Samples with the same densities were more resistant to cyclic failure if they contained higher fines contents. The state parameter provided a useful prediction for general behavioural trends of all fines contents studied.

Bender Element Measurement for Small-Strain Shear Modulus of Compacted Loess

2021 ◽  
Vol 21 (5) ◽  
pp. 04021063
Author(s):  
Fangtong Wang ◽  
Dianqing Li ◽  
Wenqi Du ◽  
Chia Zarei ◽  
Yong Liu
Keyword(s):  
Shear Modulus ◽  
Small Strain ◽  
Bender Element ◽  
Small Strain Shear Modulus ◽  
Compacted Loess

Small strain stiffness for granite residual soil: effect of stress ratio

2021 ◽  
Author(s):  
Xianwei Zhang ◽  
Xinyu Liu ◽  
Lingwei Kong ◽  
Gang Wang ◽  
Cheng Chen
Keyword(s):  
Stress Ratio ◽  
Small Strain ◽  
Residual Soil ◽  
Resonant Column ◽  
Residual Soils ◽  
Column Tests ◽  
Small Strain Stiffness ◽  
Deviator Stress ◽  
Granite Residual Soil ◽  
Stress Ratios

Most previous studies have focused on the small strain stiffness of sedimentary soil while little attention has been given to residual soils with different properties. Most studies also neglected the effects of the deviator stress, which is extensively involved in civil engineering. This note considers the effects of the deviator stress on the small-strain stiffness of natural granite residual soil (GRS) as established from resonant column tests performed under various stress ratios. Although increasing the stress ratio results in a greater maximum shear modulus for both natural and remolded residual soils, remolded soil is more sensitive to changes in the stress ratio, which highlights the effects of soil cementation. The data herein offers new insights to understand the stiffness of residual soil and other weathered geomaterials.

Sign in / Sign up

Export Citation Format

Share Document