Documents published in Scipedia

• 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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• Enhanced, statistically-controlled integrated model of geo-data based on CPTu

  J. Wierzbicki, K. Stefaniak

  ISC2024.

  
  

  Abstract

  The paper presents the possibilities of geostatistical analysis of geotechnical data using cluster analysis. As a result of the analysis, geological data from boreholes were replaced by digital data corresponding to parameters measured during CPTU static sounding. A unified database with a depth resolution of 2 cm was obtained, allowing it to be used to build geostatistical geotechnical models, e.g. using kriging. Techniques providing statistical control of the homogeneity of geotechnical separations, based only on measured data and not on interpolated or correlated data, were used to create the model. The technique used makes it possible to create an integrated geo-engineering model of the subsoil even for small sites with limited data.

  Abstract
  The paper presents the possibilities of geostatistical analysis of geotechnical data using cluster analysis. As a result of the analysis, geological data from boreholes were [...]

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• Susceptibility mapping for shallow landslides in Tierras Altas, Chiriqui, Panama : An integration of geophysical measurements

  C. Caballero, P. Castillo, J. Castrellon, S. Rodriguez, J. Gallardo

  ISC2024.

  
  

  Abstract

  The Tierras Altas region in Chiriqui, Panama presents a high agricultural activity susceptible to extreme climatic events, especially precipitation and surface runoff due to its high moisture retention capacity soils. A mountainous region with heavy winter rainfall and dry summers, part of the Chiriqui volcanic arc, and the point of triple convergence of the Coco, Nazca, and Panama microplate, also makes it a seismic threat zone. Historically, the Tierras Altas district has been susceptible to landslides, floods, and erosion-related phenomena. Through site characterization and the survey of ground dynamics, the research aims to build the input data of geological parameters and analyze dynamic properties through geophysical measurements of surface accelerations, allowing the characterization of the region and the coupling of the soil with climatic and seismic triggers. The results focus on geospatial maps and georeferenced datasets. The preliminary results were obtained through a GIS-based methodology that mapped the physical and dynamic properties of soils, identified high susceptibility zones, and analyzed how the measured dynamic data adjusted the Vs30 model.

  Abstract
  The Tierras Altas region in Chiriqui, Panama presents a high agricultural activity susceptible to extreme climatic events, especially precipitation and surface runoff due [...]

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• The Pseudo-N Values: Proposal and Practice

  K. Suto*

  ISC2024.

  
  

  Abstract

  The N-value by the standard penetration test (SPT) is commonly used for site characterisation in geotechnical engineering. S-wave velocity, typically estimated by borehole measurement or seismic survey, is also indicative of the strength of the ground. Many researchers attempted to find precise relationships between these parameters. However, N-values estimated from S-wave velocity using these formulae are subject to substantial errors, and the errors are inevitable due to the different nature of the parameters. The formula for pseudo-N value was first proposed in 2011 as (Suto, 2011). This is a simplified formula derived from the formulae found by the previous authors. By using this simple formula as a common practice, with understanding of existence of error, the results can be compared from site to site. This presentation first compares the N-value and S-wave velocity in their natures, methods, practice and cost. Then it examines the previously published formulae and proposed formula of pseudo-N value. Some examples of use of the pseudo-N values are also presented at the end.

  Abstract
  The N-value by the standard penetration test (SPT) is commonly used for site characterisation in geotechnical engineering. S-wave velocity, typically estimated by borehole [...]

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• Critical Shear-Wave Velocity Case Histories for Liquefaction Triggering Curves in Gravel

  K. Rollins, N. Salvatore*, B. Cox, T. Jackson

  ISC2024.

  
  

  Abstract

  In 2022, a new set of probabilistic shear wave velocity (𝑉𝑆) based liquefaction triggering curves was developed for gravelly soil by Rollins et al., using a dataset of 96 liquefaction and 78 no liquefaction case histories from 17 earthquakes in seven countries. Although these curves provide liquefaction assessment based on direct field performance, they suffer from the fact that there are relatively few case histories for high 𝐶𝑆𝑅 and high 𝑉𝑆 values to define the shape of the upper branch of the triggering curves. Thus, we made shear wave velocity measurements at three sites in Valdez, Alaska where liquefaction did not occur in the Mw 9.2 1964 Great Alaska earthquake. The Multi-channel Analysis of Surface Wave (MASW) technique was used to develop several median Vs profiles at each site that account for uncertainty in the experimental dispersion data and inversion parameterizations. 𝑉𝑆-based liquefaction evaluations were then made at each site, using the 𝑉𝑆 profiles derived from each solution. Results from previous Dynamic Cone Penetrometer (DPT) tests were then used in selecting the most reasonable velocity interpretation. Based on this VS profile, the layer most likely to liquefy was selected and used to define 𝑉𝑆1 and 𝐶𝑆𝑅7.5 at the middle of this critical layer, obtaining three points of no liquefaction, that could change the shape of the upper branch of the existing VS-based liquefaction triggering curves. These preliminary results suggest that it might be necessary to shift the triggering curves to the left or steepen their slope to provide better agreement with observed performance.

  Abstract
  In 2022, a new set of probabilistic shear wave velocity (𝑉𝑆) based liquefaction triggering curves was developed for gravelly soil by Rollins et al., using a [...]

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