Documents published in Scipedia

• Characteristics of the Electroresistivity of a compacted Iron Ore Tailing

  F. Marinho, B. Dos Santos, J. Da Silva*, B. Delgado, M. Hora

  ISC2024.

  
  

  Abstract

  The new legislation in Brazil has brought more attention to the technique of stacking filtered iron ore tailings for mining waste disposal. To minimize the risk of liquefaction, it's important to maintain the compacted structure in an unsaturated condition. This requires knowledge of the hydraulic characteristics of the material in order to evaluate the long-term performance of the embankment and design an adequate monitoring system. One way to track the material's behavior in the field is through electrical resistivity techniques. Using an electrical resistivity measurement system at various frequencies and current levels, we evaluated the behaviour of compacted iron ore waste. The examined tailings have been deposited in filtered tailings piles, which are intended to exceed a height of 100 meters. This study aims to investigate the electrical response of the material to different levels of water content, degree of saturation and suction. It was possible to establish good correlations between electrical resistivity and factors such as suction, degree of saturation, and water content. It was also identified an association between the electrical resistivity and the optimum water content

  Abstract
  The new legislation in Brazil has brought more attention to the technique of stacking filtered iron ore tailings for mining waste disposal. To minimize the risk of liquefaction, [...]

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• In Situ Test Methods for Thermal Site Characterisation – A Comparison

  L. Vrielink*, J. Peuchen, N. Parasie

  ISC2024.

  
  

  Abstract

  The demand for thermal site characterization has risen noticeably in the past decade, particularly for design of geothermal energy solutions and for design of in-ground power cable networks. The results of thermal characterization of a site are typically incorporated in a ground model based on environmental, geological, geophysical and geotechnical geodata. This paper compares in-situ test methods for thermal site characterization of soil. The comparison considers method applicability, deployment method, maximum test depth, test duration and uncertainty of results. A distinction is made between three categories of in-situ tests: (1) in-situ tests using active heat generation, (2) in-situ tests using passive heat generation and (3) in-situ tests with no specific thermal data acquisition

  Abstract
  The demand for thermal site characterization has risen noticeably in the past decade, particularly for design of geothermal energy solutions and for design of in-ground power [...]

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• Use of geosynthetics to close a contaminated area in a metallurgical industry in the state of bahia

  T. Andrade, I. Silva, L. Rezende, D. Eloi*, M. Neto

  ISC2024.

  
  

  Abstract

  The study for closure and monitored natural attenuation/stabilization of industrial waste deposits plays a fundamental role in the process of groundwater quality management, providing information for understanding the contaminants evolution and enabling decision-making, with the purpose of isolating waste, contaminant concentrations, toxicity and mass and/or volume reduction to levels adequate to protect human health and the environment, within a reasonable period of time. The aim of this study was to propose an environmental remediation solution for a contaminated material disposal area using the case study of a metallurgical industry located in Bahia, Brazil. To this purpose, four conditions were provided for compliance: i) control of dust, odor and erosion, ii) control of contaminant release, iii) chemical stabilization of waste and iv) soil recovery. Based on the results obtained in environmental investigation studies and information from the area, the best solution in an attempt to naturally stabilize the area would be the use of geosynthetics as a physical barrier between the contaminated material disposed in the area and the rainwater. In this way, infiltration of rainwater into the landfill and the migration of percolated liquid with risk of contamination to the soil, groundwater table and surface water bodies is avoided. It is still possible to monitor the effectiveness of the proposed solution with the installation of instrumentation such as water level indicators and piezometers.

  Abstract
  The study for closure and monitored natural attenuation/stabilization of industrial waste deposits plays a fundamental role in the process of groundwater quality management, [...]

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• Interpretation of CPTu data using machine learning techniques to develop the ground model of a dam

  M. Sottile*, J. Crocker, L. Roldan

  ISC2024.

  
  

  Abstract

  Building a ground model through manual processes can be time consuming, as large amounts of data need to be classified to define the extent and spatial distribution of the different soil materials. This paper delves into the application of machine learning (ML) methodologies, in conjunction with in-situ geotechnical testing data, to develop the ground model for a downstream dam founded on both weak and liquefiable soils. The dam covers a linear extent of approximately 800 m and was extensively characterized by means of in-situ tests, including 206 cone penetration tests (CPTu), 37 boreholes and 35 test pits. The performance of two unsupervised ML clustering algorithms are compared: Density-Based Spatial Clustering of Applications with Noise (DBSCAN) and an extended version with a hierarchical component (HDBSCAN). The clustering uses CPTu data, which consists of the normalized cone tip resistance (Qtn) and the normalized sleeve friction (Fr) varying with elevation. Nearby borehole logs are used to evaluate the results of both clustering methods for a single single CPTu sounding using different clustering parameters. Then, a global clustering including several CPTu soundings is done and results are compared with the ground model that was manually made using Leapfrog software. Both methods show very good performance, with HDBSCAN being better and more robust.

  Abstract
  Building a ground model through manual processes can be time consuming, as large amounts of data need to be classified to define the extent and spatial distribution of the [...]

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• Cyclic Cone Penetrometer Tests: Worthwhile?

  C. O'Loughlin*, F. Bransby, S. Mani, B. Bienen, P. Esfeh

  ISC2024.

  
  

  Abstract

  This paper explores the merit of including cyclic episodes in cone penetrometer tests to measure changes in sleeve resistance during cycling. Tests were carried out in a geotechnical centrifuge in a kaolin clay and a dense silica sand. The data from the tests in clay indicate that the cone sleeve mobilises the remoulded undrained shear strength during the initial penetration, but that with continued cycling, the mobilised interface shear strength reduces to around one-third of the remoulded undrained shear strength before increasing. The initial reduction is considered to be due to local consolidation around the cone sleeve (leading to total stress reduction), whereas the subsequent increase is attributed to consolidation- induced strength hardening. Tests in sand also indicate a reduction in sleeve friction during cycling, consistent with the shear band contraction mechanism associated with friction fatigue of piles in sand, but with no consolidation-induced hardening behaviour as these tests were drained. The findings suggest that cyclic cone penetrometer tests may be a convenient means of gathering data for geotechnical design for problems where the cyclic response at the clay/structure interface is of interest. Considerations on the implications for offshore site investigations are provided.

  Abstract
  This paper explores the merit of including cyclic episodes in cone penetrometer tests to measure changes in sleeve resistance during cycling. Tests were carried out in a geotechnical [...]

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• Geotechnical Characterization of Dredged Material from Rio Grande’s Port, Brazil

  I. Soares Ribeiro*, H. Nierwinski, D. Freitas Fagundes, R. Pinheiro Maria

  ISC2024.

  
  

  Abstract

  Dredging works are essential to ensure navigability in Harbors and waterways. However, this crucial activity generates millions of tonnes of waste each year worldwide. Since the disposal of dredged material is responsible for several environmental impacts, entrepreneurs and engineers must find creative uses for it. Therefore, this study aims to characterize a local dredged material to assess its properties and suitability for geotechnical applications. With this knowledge, this paper presents a series of experimental tests on dredged material samples retrieved from Rio Grande's Port, Brazil. The experimental program includes determining Atterberg limits, sieve and sedimentation analysis, pH and SEM analysis, compaction curve, and unconfined compressive strength in a reconstituted state. The results showed that the material is sandy lean clay, with unfavourable strength characteristics for geotechnical work in a raw state. However, with the advent of chemical stabilization techniques, there is potential for enhancing its suitability for geotechnical applications. By exploring methods such as adding binders like lime or Portland cement, the material's strength and stability could be significantly improved, opening up possibilities for its utilization in various engineering projects. This study contributes valuable insights into the potential reclamation and beneficial reuse of dredged material, ultimately aiding in the sustainable management of harbor and waterway dredging operations

  Abstract
  Dredging works are essential to ensure navigability in Harbors and waterways. However, this crucial activity generates millions of tonnes of waste each year worldwide. Since [...]

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• When Did Geotechnical Data Become A Point Of View: A Case Of Numerical Analysis Vs Site Data

  B. Look*

  ISC2024.

  
  

  Abstract

  The construction of a permanent bridge required a temporary bridge parallel to the permanent bridge alignment. Preloading of the permanent bridge abutment occurred under a separate early earthworks contract. That fill was removed, and the temporary structure was constructed. The fill was then replaced behind the abutment. Movement of the southern abutment of the permanent bridge was identified but with a gap of several weeks in survey monitoring due to a XMAS break period. The abutment had moved towards the river and temporary bridge. Potential causes for movement were investigated by additional investigation adjacent to and far away from the temporary bridge piles. Post movement tests carried out included: Dilatometer Testing (DMT) to assess for shear zones (if any) for slope instability, Cone Penetration Testing (CPTu) to assess strength changes (if any) to proximity of piles and new inclinometer readings. INSAR data was also obtained. A 3-D finite element analysis (FEA) carried out by a consultant matched the measured lateral displacements at the adjacent bridge. Based on that correlation, it was concluded that the removal of the close-ended temporary piles was the main cause of the excessive movement, and this initiated a contractual claim. Correlation is not causation. This case study provides a background on the site data and numerical analysis. The FEA did not include much of the site observational and site data post movement. Given the FEA was given the same credence as the site data, this suggests that data is now considered a point of view.

  Abstract
  The construction of a permanent bridge required a temporary bridge parallel to the permanent bridge alignment. Preloading of the permanent bridge abutment occurred under a [...]

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• A CT-based approach to assess sample quality in soft soils

  J. Pineda*, N. Sau, K. Ouyang, M. Arroyo

  ISC2024.

  
  

  Abstract

  The paper discusses the performance of a novel tool based on computed tomography (CT) to evaluate sample quality in soft soils. This new technique is applied to the low-plasticity Mediterranean deltaic deposits found in the region of Castello d’Empuries at the Costa Brava, in Catalonia (Spain). Tube specimens of variable diameters retrieved using open samplers (Shelby) as well as Osterberg-type fixed-piston samplers were scanned in this study. Statistical analysis of the CT images allows to define a quantitative index of sample quality. Sample quality classification based on this new non-destructive CT-based measure compares well with quality classification based on the well-established recompression sample quality index, e/e0.

  Abstract
  The paper discusses the performance of a novel tool based on computed tomography (CT) to evaluate sample quality in soft soils. This new technique is applied to the low-plasticity [...]

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• Paired in situ tests for site characterization and geotechnical design optimization

  D. Berisavljević*, N. Božović, N. Stanić

  ISC2024.

  
  

  Abstract

  The paper shows recent experience in performing and interpreting the three most common in situ tests for site characterization: cone penetration test (CPT), seismic dilatometer test (SDMT) and Menard pressuremeter Test (MPT). It is shown that an adequate selection of in situ test methods for site characterization can be used to correctly predict the pile head load-settlement curve. Menard pressuremeter design rules, which were established in the 1st and a draft version of the 2nd generation of Eurocodes, can be applied to SDMT readings to obtain the pile bearing capacity. It was found that corrected lift-off pressure p0 obtained in the SDMT test is similar to the Menard limit pressure pl in clay, while pressure p1 (SDMT) is similar to pl in sand. All results used in the analysis are obtained on a large-scale project where investigations are strictly controlled and performed in accordance with Eurocode standards.

  Abstract
  The paper shows recent experience in performing and interpreting the three most common in situ tests for site characterization: cone penetration test (CPT), seismic dilatometer [...]

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• On the Effectiveness of MOSTAP Sampling in Tailings

  P. Oelofse*

  ISC2024.

  
  

  Abstract

  The MOSTAP sampling apparatus is a popular tool in geotechnical investigation, since MOSTAP sampling can be done efficiently and cost effectively with the same rig used for CPT testing. Although few publications exist discussing the nuances and application of the MOSTAP sampler in practice, it is generally found that the MOSTAP sampler provides lower quality undisturbed samples when compared to piston tube or block samples. This paper discusses the experiences and learnings from geotechnical investigations where the MOSTAP sampler was employed in platinum and discard sand tailings in Southern Africa. A comparison between different sampler diameters at the same site showed significant improvements in sample recovery with larger diameter samplers. Ancillary equipment such as a core catcher and nylon stockings have significant effects on sample recovery and quality. The soil type and degree of saturation of samples also have a significant effect on sample recovery and sample quality. Transportation and storage of samples were identified as major contributors in moisture loss and sample disturbance. Even with the potential challenges in obtaining a representative sample at depth, MOSTAP samples are shown to be greatly beneficial in evaluating a soil profile and density determination with high confidence, especially when paired with index tests. The opportunity is identified where diligent sample measurement and tracking can provide reliable and invaluable information about a relevant soil stratum. Advanced laboratory testing (e.g., triaxial and oedometer tests) is not recommended on undisturbed MOSTAP samples, these should rather be remolded for critical state line testing, if relevant.

  Abstract
  The MOSTAP sampling apparatus is a popular tool in geotechnical investigation, since MOSTAP sampling can be done efficiently and cost effectively with the same rig used for [...]

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