Documents published in Scipedia

• Characterization of Thermal Conductivity of Backfill Materials for UPCS by Various Methods: Lab, in Situ and Numerical Analysis

  B. Dinh, Y. Kim*, C. Nguyen, G. Kang

  ISC2024.

  
  

  Abstract

  This research evaluates the thermal properties of the proposed backfill materials (prepacked concrete (PAC)) that function as the heat release medium for the underground power cable system (UPCS). First, a hot disk sensor was used to measure the thermal conductivity of small-scale backfill materials in the laboratory. The horizontal thermal response test (TRT) was then performed with a 5 × 3 × 2 m full-scale sample for the in-situ evaluation. Afterward, the data from the TRT was utilized to couple with the infinite line source model (ILS) to predict the thermal conductivity of the full-scale sample. Finally, the thermal conductivity of the PAC was back-calculated using COMSOL Multiphysics. All these tests were also performed with natural sand (conventional backfill material) to compare with the PAC. Thermal conductivities calculated by numerical simulation and the ILS model were in good agreement (difference < 3%), demonstrating that the proposed ILS model coupled with horizontal TRT data is appropriate for estimating the thermal conductivity of full-scale backfill material in situ. The results of three testing methods indicated that the prepacked concrete has a high thermal conductivity (> 2 W/(mK)), thus satisfying the heat release ability requirement for the UPCS. The laboratory test slightly underestimated the thermal conductivity (less than 8%) compared to the estimated values from the ILS model and numerical model involving prepacked concretes; however, natural sand showed a significant difference (1.365 W/(mK) and 1.8 W/(mK), 32 %) attributed to the influence of the water content change during the TRT. Therefore, it is recommended that the in-situ testing conditions should be considered for the sand (or soils) to avoid the overestimation or underestimation of their thermal conductivity.

  Abstract
  This research evaluates the thermal properties of the proposed backfill materials (prepacked concrete (PAC)) that function as the heat release medium for the underground power [...]

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• Interpreting repeated CPT in unsaturated soils

  C. Jommi*, S. Muraro, C. Chao

  ISC2024.

  
  

  Abstract

  Cone penetration tests, CPTs, are extensively used in the Netherlands to assess the stability of fourteen thousand kilometres of dykes protecting the country from flooding. On the regional dykes, site testing is planned and executed only from spring to autumn. The data collected in the drier season of the year must be used then in safety factor calculation for dyke stability with reference to the worst expected conditions, including the highest weights and the highest water pressures over the year. Inferring reliable values of the shear strength in a different season implies understanding the unsaturated response of the dyke material and the effect of variable water content on the CPT response. In previous studies referring to CPTs in unsaturated soils, it was observed that both the cone resistance and the sleeve friction depend on suction, however, only the cone resistance was used to determine the shear strength in combination with water content or suction probes installed into the ground. In this contribution, we analyse an extensive set of data, coming from repeated CPTs performed over one year on the Maasdijk near Oijen in the Netherlands. The data are elaborated to investigate whether the entire set of data can be exploited to try to derive the water content and the constant water content shear strength at the same time, if the test is repeated in different seasons.

  Abstract
  Cone penetration tests, CPTs, are extensively used in the Netherlands to assess the stability of fourteen thousand kilometres of dykes protecting the country from flooding. [...]

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• Estimation of Pore Pressure for Unsaturated-Saturated Bentonite Sand Mixture

  T. Nishimura*

  ISC2024.

  
  

  Abstract

  To investigate thermal hydration mechanical chemical couple phenomena is an important issue of the high-level radioactive waste disposal and a key indicator of artificial barrier system. Major objectives of the thermal and mechanical site characterization include the status of the environmental. Several research reports are aimed at the barrier layers for heating from radioactive waste disposal. This study appears the occurrence of the pore pressure under heat conditions for bentonite and bentonite-sand mixture material, which are completely undrained condition and unexhausted condition. It is considered that mechanics of pore pressure in macro-micro void structure due to heating-cooling repetition. A thermal chamber is used in heating method, which have high specification with accurate controlling sensitivity. The maximum temperature is 80 degrees Celsius temperatures. The prepared specimens are unsaturated specimens and saturated specimens, and silica sand are mixture into three different bentonites that various dry densities are required. Two different solutions are prepared for saturated specimen, which are distilled water and salinity water with concentration of 3.5 %. The specimens are placed into a thermostat oven, and heating application is applied isotropic conductivity. The obtained results are significant as followings; The measured pore pressures are obviously with increment of temperature, and the sand mixture ratio is small influence factor. Also, large por fluid pressures are produced for saturated condition that indication of small pore fluid pressure is verified for unsaturated specimen comparison with saturated specimen.

  Abstract
  To investigate thermal hydration mechanical chemical couple phenomena is an important issue of the high-level radioactive waste disposal and a key indicator of artificial [...]

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• In Situ Measurement of Soil Thermal Properties: a New Prototype

  A. Garcia-Fontanet*

  ISC2024.

  
  

  Abstract

  As part of the THERMALTUNNEL R&D, partially funded by Centro para el Desarrollo Tecnológico e Industrial (CDTI), a Spanish Ministry of Science and Innovation agency, PRO GEO has developed a soil penetration prototype that measures soil temperature and the thermal properties of the ground (thermal conductivity and specific heat) at different depths. The prototype is the size of a conventional CPT and contains an internal heat source with local thermocouples. A data acquisition system measures the temperature both in the prototype itself and in the surrounding ground through a penetration needle protruding from the main body of the prototype. The thermal parameters are determined by analyzing the measured heating and cooling temperature curves using the finite element codes CODE_BRIGHT (Olivella et al., 1993) and G-PFEM (Monforte, 2018). In this later numerical code, a thermal analysis module has been incorporated within the framework of the project. The operation of the prototype has been satisfactory in laboratory tests through a calibration chamber setup with granular soil under different controlled conditions of water saturation and porosity to assess the impact of those variables on the obtained values of soil thermal conductivity and specific heat. The back-analyzed parameters from the calibration chamber results have been compared with point tests (thermal conductivity and specific heat tests). The project has been developed with the cooperation of CIMNE – International Centre for Numerical Methods in Engineering.

  Abstract
  As part of the THERMALTUNNEL R&D, partially funded by Centro para el Desarrollo Tecnológico e Industrial (CDTI), a Spanish Ministry of Science and Innovation agency, PRO [...]

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• Geotechnical investigation of a fissured highly expansive clay profile

  R. Murison, T. Gaspar, S. Jacobsz, G. Heymann, Y. Narainsamy

  ISC2024.

  
  

  Abstract

  This study details some observations and challenges in interpreting site investigation data for highly expansive soils. Expansive soils exhibit large volume changes in response to changes in water content. This leads to a high degree of reworking and often a strongly fissured macrofabric in situ. A site underlain by a ~7.0 m thick active clay deposit, containing highly plastic and highly expansive smectites, was chosen for large-scale pile tests. Two identical areas were identified for the tests. The first was kept at natural water content conditions. The other was kept submerged under water through infiltration wells for six months, aiming to facilitate maximum swell of the active layers. As part of the site investigation, continuous surface wave (CSW) tests and standard penetration tests (SPT) were conducted at various points in time. These results have been compared for the natural water content and the submerged profiles. Small-strain moduli interpreted from the CSW tests showed no significant difference between the two profiles, contrary to the intuitive expectation that inundation of the highly expansive clay layers and dissipation of suctions in the order of several megapascals might significantly reduce the stiffness. Due to the small strains imposed during the test, the characteristics of the fissures and joint infill material are measured, rather than that of the intact masses. The large-strain SPT results showed a softer response for the inundated profile, as expected. Challenges in obtaining intact tube samples from the stiff and highly fissured unsaturated profile have also been discussed.

  Abstract
  This study details some observations and challenges in interpreting site investigation data for highly expansive soils. Expansive soils exhibit large volume changes in response [...]

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• 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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