Spatial and Temporal Evolution of Particle Migration in Gap-Graded Granular Soils: Insights from Experimental Observations

This study presents physical observations and insights into particle migration characteristics throughout the suffusion process. Using a purpose-built coaxial permeameter cell, suffusion experiments were conducted on idealised internally unstable gap-graded granular soils at varying fines content and hydraulic loading conditions. The specimens were prepared with a mixture layer comprising finer and coarser fractions underlying a coarse layer composed of the coarser fraction alone. This enabled the finer fraction within the mixture layer to migrate through the coarse layer with upward seepage flow. The local porosity profile along the specimen was determined using spatial time domain reflectometry and an inversion algorithm, which enabled the development of a novel field map of the difference in porosity from the initial condition. This field map provided a visual guide of the spatial and temporal variation in porosity and enabled particle migration internally within the specimen to be quantitatively characterised from onset to progression to washout. The limiting onset condition identified from the field map was shown to be comparable to that obtained using conventional approaches, thereby providing strong validation for the application of porosity-based field maps. As suffusion progressed, the height of infiltrating finer particles into the coarse layer increased linearly with time, while the overall rate of particle migration from the mixture layer to the coarse layer evolved in a non-linear manner with the rate of migration increasing as the specimen reached a complete mixture condition, where the finer fraction infiltrated the entire coarse layer. The attainment of a complete mixture condition was dependent on the fabric of the gap-graded soil ... (see PDF for full abstract).Comment: 28 pages, 20 figures. Article published in Journal of Geotechnical and Geoenvironmental Engineering 2023 (see https://ascelibrary.org/doi/10.1061/JGGEFK.GTENG-11094

Dielectric relaxation behavior of Callovo-Oxfordian clay rock: A hydraulic-mechanical-electromagnetic coupling approach

Water content is a key parameter to monitor in nuclear waste repositories such as the planed underground repository in Bure, France, in the Callovo-Oxfordian (COx) clay formation. High-frequency electromagnetic (HF-EM) measurement techniques, i.e., time or frequency domain reflectometry, offer useful tools for quantitative estimation of water content in porous media. However, despite the efficiency of HF-EM methods, the relationship between water content and dielectric material properties needs to be characterized. Moreover, the high amount of swelling clay in the COx clay leads to dielectric relaxation effects which induce strong dispersion coupled with high absorption of EM waves. Against this background, the dielectric relaxation behavior of the clay rock was studied at frequencies from 1 MHz to 10 GHz with network analyzer technique in combination with coaxial transmission line cells. For this purpose, undisturbed and disturbed clay rock samples were conditioned to achieve a water saturation range from 0.16 to nearly saturation. The relaxation behavior was quantified based on a generalized fractional relaxation model under consideration of an apparent direct current conductivity assuming three relaxation processes: a high-frequency water process and two interface processes which are related to interactions between the aqueous pore solution and mineral particles (adsorbed/hydrated water relaxation, counter ion relaxation and Maxwell-Wagner effects). The frequency-dependent HF-EM properties were further modeled based on a novel hydraulic-mechanical-electromagnetic coupling approach developed for soils. The results show the potential of HF-EM techniques for quantitative monitoring of the hydraulic state in underground repositories in clay formations

A niche application of permanent CO2 disposal from coal-fired power stations via mineralisation in proximal mafic and ultramafic deposits

Australia\u27s coal-fired power stations accounted for approximately 23% of the country\u27s total Green House Gas (GHG) emissions from all power stations in the 2021-2022 period. These emissions encompass both Scope 1 and Scope 2 categories. Such a significant contribution has led to continuous criticism of the coal industry within Australia, as the global energy landscape shifts towards a broader range of low to zero-emission energy sources. This transition calls for the coal industry to explore innovative methods to capture and remove Green House Gas emissions, particularly CO2, which is a major contributor to global warming. Current CO2 disposal methodologies are predominantly focused on injecting CO2 into deep aquifers and depleted oil and gas reservoirs. In this paper, we propose an alternative approach for the permanent disposal of CO2 emissions from coal-fired power stations. This approach involves the underground injection of CO2 into ultramafic and mafic deposits located within economical distances from these stations in Southeast Australia. The exothermic reactions between CO2 and magnesium- and calcium-rich minerals in ultramafic and mafic rocks lead to the permanent conversion of CO2 into stable carbonate minerals. This process eliminates the need for extensive monitoring and control systems to detect any unintended CO2 seepage on the surface and is expected to lower the running costs of CO2 disposal

Dielectric spectroscopy measurements on kaolin suspensions for sediment concentration monitoring

Sedimentation along with consolidation processes dictate the in situ engineering and hydraulic behavior of a particulate system such as soil. With this in view, the present investigation discusses about the application of dielectric measurements in relation to sediment concentration measurements for fine grained soils. An in-house set up comprising of open ended coaxial probes and vector network analyzer has been used to measure the dielectric behavior of kaolin suspensions in tap and deionized water. These have been further analyzed to furnish suspended sediment concentration, pore water conductivity and shape factors utilizing Complex Refractive Index Model (CRIM) and Bruggeman–Hanai–Sen (BHS) model, through the implementation of an optimization scheme. Furthermore, measured and estimated suspended sediment concentrations showed good agreement with each other in terms of statistical parameters, and a ranking of models approach reliant on three statistical criteria revealed that, CRIM outperforms BHS model for estimating sediment concentrations

Dielectric relaxation behavior of Callovo-Oxfordian clay rock: A hydraulic-mechanical-electromagnetic coupling approach

Water content is a key parameter to monitor in nuclear waste repositories such as the planed underground repository in Bure, France, in the Callovo-Oxfordian (COx) clay formation. High-frequency electromagnetic (HF-EM) measurement techniques, i.e., time or frequency domain reflectometry, offer useful tools for quantitative estimation of water content in porous media. However, despite the efficiency of HF-EM methods, the relationship between water content and dielectric material properties needs to be characterized. Moreover, the high amount of swelling clay in the COx clay leads to dielectric relaxation effects which induce strong dispersion coupled with high absorption of EM waves. Against this background, the dielectric relaxation behavior of the clay rock was studied at frequencies from 1 MHz to 10 GHz with network analyzer technique in combination with coaxial transmission line cells. For this purpose, undisturbed and disturbed clay rock samples were conditioned to achieve a water saturation range from 0.16 to nearly saturation. The relaxation behavior was quantified based on a generalized fractional relaxation model under consideration of an apparent direct current conductivity assuming three relaxation processes: a high-frequency water process and two interface processes which are related to interactions between the aqueous pore solution and mineral particles (adsorbed/hydrated water relaxation, counter ion relaxation and Maxwell-Wagner effects). The frequency-dependent HF-EM properties were further modeled based on a novel hydraulic-mechanical-electromagnetic coupling approach developed for soils. The results show the potential of HF-EM techniques for quantitative monitoring of the hydraulic state in underground repositories in clay formations. Key Points Dielectric relaxation behavior of porous mediaRadio and microwave remote sensing techniquesHydraulic-mechanical-electromagnetic couplin

Introduction of flat ribbon cable (FRC) sensor for density measurement of road materials using time domain reflectometry (TDR)

Moisture content and density of unbound granular pavement materials are important properties for compaction control providing a great influence on pavement performance. Time domain reflectometry (TDR) usually uses rod probe sensors, which can provide pointwise readings of density. However, pointwise readings might not be representative enough for a complete road section. This paper introduces the application of flat ribbon cable (FRC) sensor, which can be extended up to 6 meter to measure moisture and density of road materials. Soil specific calibration is done in the laboratory considering the variation of moisture and density of materials where sensors of three different lengths are considered to enable the development of length normalized calibration. The electric parameter used to derive soil density is the voltage drop, which occurs after the passage of an electromagnetic wave along the sensor embedded in the soil. Soil moisture is related to the permittivity of the soil sample, which is obtained from the travel time of the TDR signal. Laboratory results indicate that calibration functions are independent of moisture and density. These soil specific calibration functions are useful in measuring long term pavement performance and managing rutting of roads

Réflectométrie fréquentielle (FDR) appliquée à l'évaluation non destructive des conduits de précontrainte extérieure, perspective pour la mesure de la teneur en eau du béton

National audienceThis paper presents an electromagnetic method of diagnosis based on frequency domain reflectometry (FDR) associated with an inversion algorithm developed by INRIA, ISTLTM (Inverse Scattering for Transmission Lines). ISTLTM allows estimating the spatial profile of the electrical impedance of the line from the FDR measurements. Experimental results on two mockups of external post-tensioned ducts with filling defects show the feasibility of the method. We will try to show the similarities between auscultation external post-tensioned ducts and measurement of water content by TDR probes (Time Domain Reflectometry).Ce papier présente une méthode électromagnétique de diagnostic reposant sur la réflectométrie fréquentielle (FDR) associée à un algorithme d'inversion développé par l'INRIA, ISTLTM (Inverse Scattering for Transmission Lines). ISTLTM permet d'estimer le profil spatial d'impédance électrique de la ligne à partir de la mesure FDR. Des résultats expérimentaux obtenus sur deux maquettes de conduits de précontrainte extérieure ayant des défauts de remplissage montrent la faisabilité de la méthode. Nous tacherons de montrer les similitudes qui existent entre l'auscultation des conduits de précontrainte extérieure et la mesure de teneur en eau par des sondes TDR (Time Domain Reflectometry)

Improvement of the diagnosis of the damage of post tensioned ducts using capacitive probe

Les travaux présentés dans cette thèse contribuent au développement du contrôle non destructif des conduits de précontrainte extérieure dans les ouvrages d'art. Une sonde capacitive a été développée pour ausculter ces conduits. L'objectif est d'en améliorer le diagnostic.Dans un premier temps, une cellule de mesure en transmission coaxiale a été développée pour caractériser les matériaux présents dans le conduit sur la bande de fréquence 50 MHz - 1 GHz. Le ciment, les produits de la ségrégation du ciment et la cire d'injection ont été étudiés.La deuxième partie du travail exploite ces résultats dans une modélisation directe du problème global. Une étude paramétrique nous a permis de proposer une méthode d'estimation de l'épaisseur de vide à l'intérieur du conduit à partir des signaux délivrés par la sonde, qui a pu être validée sur une maquette de conduit. A partir de ces résultats sont proposées plusieurs améliorations du dispositif visant à l'obtention de signaux plus riches issus des capteurs, afin de pouvoir estimer un plus grand nombre de paramètres.The work presented in this report contributes to the development of Non Destructive Evaluation of the external post-tensioned ducts in bridges. A capacitive probe has been developed for bridge monitoring applications. The aim of this work is to improve its diagnostic.In a first step, a coaxial transmission line was developed to characterize the materials involved in the duct over the frequency range 50 MHz - 1 GHz. The cement grout, segregation products of the cement grout and the injection wax were studied.In the second part of this work the previous results are used in the modelling of the devices. A parametrical study has shown the ability to get from the signals an estimate of the thickness of the void in the duct. This estimation method has been validated using a laboratory duct. Further, several improvements of the probes are proposed to get signals containing more information in order to get a better estimation of the target parameters