Documents published in Scipedia

• Geotechnical Parameters of Filtered Tailings and Waste Rock from the Itabira Complex used in Stacking Projects

  D. Eloi*, M. Paganin, D. Bastos, W. Maciel, M. Filho, R. Silva

  ISC2024.

  
  

  Abstract

  The complex where we used the materials ins this study, explores iron ore in an open pit process and is formed by a significant number of mines, and all their geotechnical structures such as waste rock stackings, tailings dams and, recently, the stackings that are being constructed with waste rock and tailings. For the piles formed by the shared disposal of waste rocks and filtered tailings, the characterization of the materials and the strength and critical state parameters determined the executive methodology and the safety factors required for the projects. The waste rocks and filtered tailings are mechanically disposed and divided into zones defined not only according to the geotechnical characteristics of the materials, but also the structural and operational needs of the stacking, which are divided into the confining zone and the confined zone. In the confining zone, compacted waste is deposited. The aim of this procedure is to enhance the structural performance by employing materials with higher resistance. In the confining zone, as closer to the outer layer of the pile, greater shear strength is mobilized. In the confined zone, friable waste, and mining tailings are disposed. In this zone, there is less mobilization of shear strength. For tailings, control and evaluation adhere to parameters outlined by the Critical State Line, employing the void ratio control of layers. This ensures dilatant mechanical behaviours for all confinement stresses specified in the project.

  Abstract
  The complex where we used the materials ins this study, explores iron ore in an open pit process and is formed by a significant number of mines, and all their geotechnical [...]

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• Effects of Vane Size and Aspect Ratio on the Measurement of Undrained Shear Strength of a Fine-Grained Soil

  T. Chatfield*, R. Rinehart, C. Fontaine

  ISC2024.

  
  

  Abstract

  The field Vane Shear Test (VST) is a widely used in-situ test method to measure undrained shear strength and sensitivity of saturated, fine-grained soils. The United States Bureau of Reclamation (Reclamation) commonly performs this test method to help inform numerical modeling of earth embankment dams when undergoing a risk analysis or design. Although the test method itself has been a geotechnical tool for quite some time, its primary use has traditionally been limited to sites with soft and/or relatively shallow clay soil. Typically, embankment and foundation materials of interest at Reclamation facilities are at greater depths, under higher effective stresses, and can be relatively stiff. Testing of stronger soils poses issues when performing the VST; typical commercially available equipment has a limited torque capacity to cause yielding of the soil. As a solution, modifying the dimensions and aspect ratio of the vane is an economic means of increasing the measurable range of undrained strength. Yet, the effects of these modifications are not well understood. Soil strength anisotropy is one of the primary components of this uncertainty. Testing on a sandy lean clay has been conducted to enable side by side comparisons of traditional aspect ratio vanes versus the proposed modified vanes to quantify the potential differences in measured undrained strength. In addition, measured undrained strengths from the various vanes are compared to results of laboratory testing on the same sandy lean clay (i.e., direct simple shear and triaxial compression) to provide a better understanding of the differences between the in-situ and laboratory test methods. This paper presents the apparatus developed to allow full scale vane shear tests to be conducted in the laboratory and summarizes the results of tests on a normally consolidated sandy lean clay.

  Abstract
  The field Vane Shear Test (VST) is a widely used in-situ test method to measure undrained shear strength and sensitivity of saturated, fine-grained soils. The United States [...]

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• Analysis of Shear and Consolidation Behaviour of a Clay Foundation Below a Tailings Storage Facility

  T. Armstrong*, T. Grobler

  ISC2024.

  
  

  Abstract

  Historically, the analyses of tailings storage facilities (TSFs) have primarily focused on understanding the characteristics of tailings, while often overlooking a comprehensive evaluation of the foundation, as seen at Mount Polley in 2014. The Global Industry Standard on Tailings Management (GISTM) Requirement 5.4 stresses the importance of comprehensively addressing all potential failure modes. Numerous platinum TSFs in Southern Africa are underlain by residual clay, specifically a residual mafic rock from the Bushveld Complex. Similar soils, known as "tropical black clay soils", are found in other regions of the world. Surprisingly, there's limited public information on testing and modelling the behaviour of this clay foundation. This paper presents a case study that employs a novel approach to assess the impact of loading from tailings deposition on the underlying clay foundation of an upstream TSF. The analysis investigates how shear behaviour and consolidation characteristics of the clay foundation change with varying TSF heights and construction rates. The approach includes quantifying excess pore water pressures and their influence on the clay foundation's effective stress. The analyses primarily employ traditional limit equilibrium methods to assess TSF stability and foundation behaviour, with the potential to expand to numerical modelling. The study concludes that excess pore water pressures will significantly affect the Factor of Safety (FoS) of a TSF, particularly with adverse consolidation characteristics and increasing TSF height. This is primarily due to the low permeability and changing consolidation coefficient (cv) of the clay layer as the surcharge load increases. Furthermore, the research reveals that, depending on the rate of rise, tailings deposition may induce excess pore water pressures, potentially reducing the FoS. The ability to quantify excess pore water pressures using this novel approach enables a more accurate estimation of the FoS for facilities underlain by low-permeability materials, either residual or transported.

  Abstract
  Historically, the analyses of tailings storage facilities (TSFs) have primarily focused on understanding the characteristics of tailings, while often overlooking a comprehensive [...]

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• Temperature based Leakage Detection and Monitoring Systems in view of Tailings Storage Facilities

  G. Dumont, A. Fabritius*

  ISC2024.

  
  

  Abstract

  Characterizing the in-situ state of soils is essential for evaluating their vulnerability and the consequences of failure. The cone penetration test (CPT) enables efficient, repeatable, and continuous soil characterization based on the recorded response to penetration. Particularly for waste storage facilities, analysis of CPT results can help avoid failures that could lead to significant socio-economic and environmental impacts. Human-made soils in waste storage facilities, like coal combustion products and mine tailings, can have a large fraction of silt-sized particles, which makes them prone to experiencing partial drainage during CPT soundings at standard penetration rates. However, the current state of practice still predominantly adopts the assumption of fully drained or undrained conditions, which may lead to inaccurate interpretation of soil properties and state. This study aims to explore a new CPT-based characterization framework for intermediate silty soils using cone tip resistance values to determine the soil state. To do so, CPT soundings were performed in-flight in centrifuge models of a coal combustion product with different initial densities at varying penetration velocities. Soils with a low density and contractive behavior experience a decrease in tip resistance as the penetration velocity is increased due to the generation of excess pore pressures, resulting in high ratios of drained to undrained tip resistance (Qtn,drained/Qtn,undrained). In contrast, the tip resistance increases with penetration velocity, resulting in low Qtn,drained/Qtn,undrained ratios in soils of a high density and dilative behavior. The proposed framework uses Qtn,drained/Qtn,undrained to identify contractive layers and is expected to help assess the vulnerability of soil layers to experience liquefaction failure.

  Abstract
  Characterizing the in-situ state of soils is essential for evaluating their vulnerability and the consequences of failure. The cone penetration test (CPT) enables efficient, [...]

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• Characterization of coal combustion products using variable rate CPT in a geotechnical centrifuge

  J. Chen, A. Martinez

  ISC2024.

  
  

  Abstract

  Characterizing the in-situ state of soils is essential for evaluating their vulnerability and the consequences of failure. The cone penetration test (CPT) enables efficient, repeatable, and continuous soil characterization based on the recorded response to penetration. Particularly for waste storage facilities, analysis of CPT results can help avoid failures that could lead to significant socio-economic and environmental impacts. Human-made soils in waste storage facilities, like coal combustion products and mine tailings, can have a large fraction of silt-sized particles, which makes them prone to experiencing partial drainage during CPT soundings at standard penetration rates. However, the current state of practice still predominantly adopts the assumption of fully drained or undrained conditions, which may lead to inaccurate interpretation of soil properties and state. This study aims to explore a new CPT-based characterization framework for intermediate silty soils using cone tip resistance values to determine the soil state. To do so, CPT soundings were performed in-flight in centrifuge models of a coal combustion product with different initial densities at varying penetration velocities. Soils with a low density and contractive behavior experience a decrease in tip resistance as the penetration velocity is increased due to the generation of excess pore pressures, resulting in high ratios of drained to undrained tip resistance (Qtn,drained/Qtn,undrained). In contrast, the tip resistance increases with penetration velocity, resulting in low Qtn,drained/Qtn,undrained ratios in soils of a high density and dilative behavior. The proposed framework uses Qtn,drained/Qtn,undrained to identify contractive layers and is expected to help assess the vulnerability of soil layers to experience liquefaction failure.

  Abstract
  Characterizing the in-situ state of soils is essential for evaluating their vulnerability and the consequences of failure. The cone penetration test (CPT) enables efficient, [...]

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• Cone penetration test assessment to identify fluid-like tailings to support a tailings storage facility deconstruction

  G. Quaglia*, I. Cueto

  ISC2024.

  
  

  Abstract

  This paper presents the implementation of a Cone Penetration Test (CPT)-based methodology to identify fluid-like tailings in the Tailings Storage Facility (TSF) pond to support a TSF deconstruction. The TSF discussed in this paper was partially raised upstream and classified as very high risk due to its location, next to a creek and a short distance to the downstream community. The owner's preferred mitigation strategy was to proceed with the TSF deconstruction. To inform the deconstruction planning, a comprehensive geotechnical site investigation was conducted, which included CPTu and boreholes with continuous thin wall tube sampling from a floating platform. The investigation identified tailings in the pond as high plasticity clays (CH) with a geotechnical fines content exceeding 95 %. The CPT results indicated low tip resistance, nearly linear pore pressure measurements, and minimal sleeve friction, suggesting the presence of fluid-like tailings in a significant portion of the TSF. The implementation of this methodology allowed to systematically confirm the presence of fluid-like tailings across the pond and define their extent. This information supported the owner’s decision to employ mechanical excavation taking advantage of the tailings flowability. The observations made during the tailings excavation confirmed a good agreement between the CPT assessment and the actual material behaviour. These findings underscore the efficacy of the CPT-based method in guiding safe TSF deconstruction projects

  Abstract
  This paper presents the implementation of a Cone Penetration Test (CPT)-based methodology to identify fluid-like tailings in the Tailings Storage Facility (TSF) pond to support [...]

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• Evaluating the dynamic liquefaction potential of tailings: a comparison of simplified methods

  L. Roldan, F. Spinazzola*, M. Sottile

  ISC2024.

  
  

  Abstract

  The state of the practice to evaluate the dynamic liquefaction potential of a soil column entails the use of simplified methods that compares the cyclic stress ratio with the cyclic resistance ratio. One of the most used methods is the Boulanger & Idriss 2014, which relies on cone penetration test data to estimate in-situ cyclic resistance ratio and cyclic stress ratio distributions, considering corrections factors for soils with fine contents. Saye, Olson and Franke in 2021 presented a novel method to assess liquefaction susceptibility using cone penetration test data on soils ranging from non-sensitive clays to clean sands. The procedure was developed using +400 documented case records of liquefaction and non-liquefaction in clean sands, silty sands, sandy silts, and low plasticity fine grained soils. Although promising, this method is not widely used in the industry yet. This paper presents a comparison between both methods for tailings. It uses cone penetration test soundings performed in tailings with a wide range of mineralogy and fine contents, combined with variations in peak ground accelerations and magnitudes. This analysis shows that Saye, Olson and Franke’s method is generally more robust, particularly for the analysis of fine tailings, as Boulanger & Idriss’ method relies on site specific data or the engineer’s judgement to define an Ic cut-off value that screens out clay-like soils from the liquefaction analysis.

  Abstract
  The state of the practice to evaluate the dynamic liquefaction potential of a soil column entails the use of simplified methods that compares the cyclic stress ratio with [...]

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• Correlation Between Shear Wave Velocity From Borehole Seismic and CPT Data for the Application of Numerical Analysis

  U. Matthiesen*, M. Pohl

  ISC2024.

  
  

  Abstract

  The Federal Waterways and Shipping Administration of Germany is currently planning the construction of a lock next to the existing Lueneburg twin ship lift on the Elbe Lateral Canal. The vertical lift of both the ship lift and the new lock is 38 m. The lock will be the biggest of its kind worldwide and will require an excavation pit of about 260 m length, 60 m width and 26 m depth. The adjacent ship lift is a major constraining factor for the project, as it must remain in operation throughout construction and thereafter. As part of an extensive site investigation, geophysical crosshole measurements were carried out up to a depth of 70 m to obtain dynamic soil properties necessary for the numerical analyses. This paper shows the results of the geophysical survey as well as a comparison of the in-situ measurements with well-established CPT correlations. The comparison shows a moderate to good match for the dynamic soil parameters such as the smallstrain shear modulus Gmax or the shear wave velocity Vs respectively, providing confidence in the derived soil parameters across the site.

  Abstract
  The Federal Waterways and Shipping Administration of Germany is currently planning the construction of a lock next to the existing Lueneburg twin ship lift on the Elbe Lateral [...]

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• Probabilistic soil model for seismic risk assessment based on SDMT results

  Y. Vargas-Alzate*, D. Tarragó, A. Zapata-Franco, A. Gens

  ISC2024.

  
  

  Abstract

  A new geotechnical site investigation has been conducted in the southern breakwater basin of the Port of Barcelona, for which hundreds of in-situ and lab tests have been performed. Among these tests, this study focuses on the evaluation of triple points. That is, at the prospected locations, there are results from seismic dilatometer Marchetti test (SDMT), cone penetration tests (CPTu), and laboratory tests based on soil samples. Based on this information, the probabilistic distribution of the dynamic and geometrical properties of the soil profiles can be properly characterized. Eleven closely spaced boreholes have been used to characterise the statistical properties of the input variables. The objective of this article is twofold. First, the probabilistic generation of one-thousand soil profiles, which are statistically compatible with the data provided by the eleven aforementioned boreholes. Secondly, to analyse how the elastic properties of the generated soil profiles evolve once seismic waves have passed through them. To do so, a large set of ground motion recorded in hard soils have been employed. Results show that the dynamic response of the soil can be properly parametrized if considering intensity measures extracted from the ground motions acting at the bedrock level. From the results obtained, fragility functions have been derived for risk assessment purposes.

  Abstract
  A new geotechnical site investigation has been conducted in the southern breakwater basin of the Port of Barcelona, for which hundreds of in-situ and lab tests have been performed. [...]

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• Estimation of the Soil Unit Weight of Mining Tailings through the Application of Machine Learning Techniques

  H. Nierwinski, T. Menegaz*, E. Odebrecht, F. Schnaid, R. Pfitscher, F. Mantaras

  ISC2024.

  
  

  Abstract

  There are several correlations in the literature that allow an estimate of the soil unit weight for natural soils, but when dealing with materials whose actual specific gravity of solids is outside the range of natural soils for which the correlations were developed, doubts arise, as occurs in the interpretation of tests on mining tailings. Therefore, the present paper aims to evaluate the application of a previously developed approach supported by machine learning techniques for estimating soil specific weights for mining tailings. This approach was developed considering a more comprehensive range of the specific gravity of solids. So, this work relies on a database with results of CPTu tests carried out in different mining tailings deposits from Brazil to estimate specific weights. The values of the specific weights obtained from the machine learning model were compared with literature data, presenting a suitable fit. The research demonstrates that artificial intelligence can contribute positively to the estimation of reliable design parameters and add security to the development of designs of mining tailings containment structures.

  Abstract
  There are several correlations in the literature that allow an estimate of the soil unit weight for natural soils, but when dealing with materials whose actual specific gravity [...]

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