Static liquefaction of Merriespruit gold tailings

2021 ◽  
pp. 61-72
Author(s):  
George Papageorgiou ◽  
Andy B. Fourie ◽  
Geoff E. Blight
Keyword(s):  
Static Liquefaction ◽  
Gold Tailings

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.

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.

Static liquefaction as a possible explanation for the Merriespruit tailings dam failure

2001 ◽  
Vol 38 (4) ◽  
pp. 707-719 ◽  
Author(s):  
A B Fourie ◽  
G E Blight ◽  
G Papageorgiou
Keyword(s):  
South Africa ◽  
Steady State ◽  
Companion Paper ◽  
Dam Failure ◽  
Triaxial Tests ◽  
Tailings Dam ◽  
Failure Investigation ◽  
Static Liquefaction ◽  
Gold Tailings

In 1994 the Merriespruit gold tailings dam in South Africa failed, resulting in 17 deaths. The post-failure investigation provided no explanation as to why the catastrophic flow failure, which contradicted all previous experiences of failures of gold tailings dams in South Africa, occurred. The documented history of the dam describes insufficient freeboard provision and often poor pool control, which is argued to have resulted in some areas of the dam having high in situ void ratios. Some of the undrained triaxial tests carried out on specimens obtained from zones adjacent to the failure scar exhibited nondilative behaviour. Laboratory triaxial tests that were conducted on reconstituted specimens and are reported in a companion paper defined a series of steady state lines that were dependent on the particle-size distribution of the tailings. Void ratios obtained from undisturbed samples taken during the post-failure investigation are compared with these steady state lines and it is shown that an appreciable percentage of the specimens were likely to have been contractant. The inference drawn is that a large volume of tailings was in a metastable state in situ and overtopping and erosion of the impoundment wall exposed this material, resulting in static liquefaction of the tailings and a consequent flow failure.Key words: static liquefaction, gold tailings, Merriespruit, failure.

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.

scholarly journals Prediction of Effects of Geogrid Reinforced Granular Fill on the Behaviour of Static Liquefaction

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
A. Hemalatha ◽  
N. Mahendran ◽  
G. Ganesh Prabhu
Keyword(s):  
Bearing Capacity ◽  
Load Test ◽  
Test Results ◽  
Plate Load Test ◽  
Large Size ◽  
Static Liquefaction ◽  
Granular Fill ◽  
Size Dimension ◽  
Subgrade Modulus ◽  
Different Thickness

The experimental investigation on the effects of granular fill and geogrid reinforced granular fill on the behaviour of the static liquefaction potential of the subsoil is reported in this study. A series of plate load test were carried out with different thickness of the granular fill, number of geogrid layers, and size/dimension of the footing. The test results were presented in terms of bearing capacity and subgrade modulus for the settlement ofδ10,δ15, andδ20. The experimental results revealed that the introduction of granular fill significantly increases the bearing capacity and effectively control the settlement behaviour of the footing. The introduction of geogrid in granular fill enhanced the Percentage of Control in Settlement and Bearing Capacity Ratio by a maximum of 328.54% and 203.41%, respectively. The introduction of geogrid in granular fill interrupts the failure zone of the granular fill and enhances the subgrade modulus of the footing by a maximum of 255.55%; in addition subgrade modulus of the footing was increased with an increase in the number of geogrid layers. Based on the test results it is suggested that the footing with large size has beneficial improvement on the reinforced granular fill.

Thermo-mechanical properties and microfabric of fly ash-stabilized gold tailings

2014 ◽  
Vol 276 ◽  
pp. 323-331 ◽  
Author(s):  
Joon Kyu Lee ◽  
Julie Q. Shang ◽  
Sangseom Jeong
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Gold Tailings

Reliability analysis of static liquefaction of loose sand using the random finite element method

2015 ◽  
Vol 32 (7) ◽  
pp. 2100-2119 ◽  
Author(s):  
Ali Johari ◽  
Jaber Rezvani Pour ◽  
Akbar Javadi
Keyword(s):  
Finite Element ◽  
Pressure Ratio ◽  
Monotonic Loading ◽  
Unit Weight ◽  
Soil Parameters ◽  
Loose Sand ◽  
Element Analysis ◽  
Content Type ◽  
Static Liquefaction ◽  
Random Finite Element

Purpose – Liquefaction of soils is defined as significant reduction in shear strength and stiffness due to increase in pore water pressure. This phenomenon can occur in static (monotonic) or dynamic loading patterns. However, in each pattern, the inherent variability of the soil parameters indicates that this problem is of a probabilistic nature rather than being deterministic. The purpose of this paper is to present a method, based on random finite element method, for reliability assessment of static liquefaction of saturated loose sand under monotonic loading. Design/methodology/approach – The random finite element analysis is used for reliability assessment of static liquefaction of saturated loose sand under monotonic loading. The soil behavior is modeled by an elasto-plastic effective stress constitutive model. Independent soil parameters including saturated unit weight, peak friction angle and initial plastic shear modulus are selected as stochastic parameters which are modeled using a truncated normal probability density function (pdf). Findings – The probability of liquefaction is assessed by pdf of modified pore pressure ratio at each depth. For this purpose pore pressure ratio is modified for monotonic loading of soil. It is shown that the saturated unit weight is the most effective parameter, within the selected stochastic parameters, influencing the static soil liquefaction. Originality/value – This research focuses on the reliability analysis of static liquefaction potential of sandy soils. Three independent soil parameters including saturated unit weight, peak friction angle and initial plastic shear modulus are considered as stochastic input parameters. A computer model, coded in MATLAB, is developed for the random finite element analysis. For modeling of the soil behavior, a specific elasto-plastic effective stress constitutive model (UBCSAND) was used.

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