Cone Penetration Testing 2022

This volume contains the proceedings of the 5th International Symposium on Cone Penetration Testing (CPT’22), held in Bologna, Italy, 8-10 June 2022. More than 500 authors - academics, researchers, practitioners and manufacturers – contributed to the peer-reviewed papers included in this book, which includes three keynote lectures, four invited lectures and 169 technical papers. The contributions provide a full picture of the current knowledge and major trends in CPT research and development, with respect to innovations in instrumentation, latest advances in data interpretation, and emerging fields of CPT application. The paper topics encompass three well-established topic categories typically addressed in CPT events: - Equipment and Procedures - Data Interpretation - Applications. Emphasis is placed on the use of statistical approaches and innovative numerical strategies for CPT data interpretation, liquefaction studies, application of CPT to offshore engineering, comparative studies between CPT and other in-situ tests. Cone Penetration Testing 2022 contains a wealth of information that could be useful for researchers, practitioners and all those working in the broad and dynamic field of cone penetration testing

Imaging and discrete modelling of sand shape

The shape of particles is known to play an important role in soil behaviour, with significant effects of engineering responses. Investigating how the shape of particles can be measured and quantified is therefore considered increasingly important in modern soil mechanics. This is propelled by the advent of computer based image-analyses and discrete modelling algorithms, which have opened new ways to tackle this problem. This work demonstrates how these two techniques can be made to work together. Image analyses are performed on x-rays micro-tomographs (µ-CT) of triaxial sand specimens, focusing on the characterisation and quantification of particle shapes. Two with very different particle shape sands are studied in details: Caicos ooids (rounded) and Hostun sand (angular). A discrete Digital Volume Correlation (DVC) algorithm is then used to track the kinematics of individual grains (around 50000 for each sand specimen) during the triaxial test and measure, with good precision, their cumulated displacements and rotations. Joint analysis of the shape and kinematic databases acquired is performed to find how particle shape descriptors are related to observed kinematics at the microscale level. It appears that true sphericity is a good predictor of upper bound rotational restraint. Modelling is based on the Discrete Element Method (DEM). Models that introduce rolling resistance at the contact are widely employed in DEM simulations, these approaches offer substantial computational benefits at the prize of increased calibration complexity. In this work, the values of true sphericity obtained by image analysis of the grains, either directly by 3D acquisition or by correlation with simpler to obtain 2D shape measures, are used to establish mechanically equivalent rotational restrictions. An empirical relation between a contact parameter (rolling friction) and a 3D grain shape descriptor (true sphericity is first calibrated - using both specimen-scale and grain scale results from two triaxial tests in Hostun sand and Caicos ooids. It is then validated by simulating other triaxial tests (1) with the same sands, but in different conditions (2) with Ottawa sand, for which 3D grain images were also available for examination, and (3) with Ticino sand, for which only 2D grain images were available. Finally, results of large-scale DEM simulations on the Cone Penetration Test (CPT) - exploiting the new proposed contact model - are presented. Experimental data on the CPT performed in a Calibration Chamber (CC) comprised of Ticino sand are successfully fitted by the numerical penetration curves at different confining pressures and conditions. A parametric study about the influence of particle shape and particle shape variability put in evidence the strong-coupled effects of rolling and frictional resistances at the particles contacts. The work described in this thesis will ease the use of DEM for large-scale simulations of geotechnical engineering problems.Se sabe que la forma de las partículas juega un papel importante en el comportamiento del suelo, con efectos significativos de las respuestas mecánicas relevantes en ingeniería geotécnica. Por lo tanto, investigar cómo se puede medir y cuantificar la forma de las partículas se considera cada vez más importante en la mecánica del suelo moderna. Esto se acrecienta debido a las técnicas de análisis computacionales de imágenes y algoritmos de modelado discreto (DEM), que han abierto nuevas formas de abordar este problema. Este trabajo demuestra cómo se pueden hacer que estas dos técnicas funcionen juntas. Los análisis de imagen se realizan sobre micro-tomografías de rayos X (µ-CT) de muestras de arena en celdas triaxiales, centrándose en la caracterización y cuantificación de la forma de las partículas. Se estudian en detalle dos arenas con la forma de sus partículas muy diferentes: Caicos ooids (redondeados) y Hostun sand (angular). Luego se utiliza un algoritmo discreto de correlación de volumen digital (DVC) para rastrear la cinemática de granos individuales (alrededor de 50000 por cada muestra de arena) durante la prueba triaxial y medir, con buena precisión, sus desplazamientos y rotaciones acumulados. El análisis conjunto de la forma y las bases de datos cinemáticas adquiridas se realiza para encontrar cómo los descriptores de forma de partículas se relacionan con la cinemática observada a nivel de micro-escala. Resulta que la esfericidad verdadera predice bien el límite superior de rotación de una partícula. La modelización numérica se basa en el Método de Elementos Discretos (DEM). Los modelos que introducen resistencia a la rotación en el contacto se emplean ampliamente en simulaciones DEM, estos enfoques ofrecen beneficios computacionales sustanciales a costa de una mayor complejidad de calibración. En este trabajo, los valores de esfericidad verdadera (i.e., true sphericity) obtenidos mediante análisis de imagen de los granos, ya sea directamente por adquisición 3D o por correlación con medidas de forma 2D más simples, se utilizan para establecer restricciones de rotación mecánicamente equivalentes. Una relación empírica entre un parámetro de contacto (rolling friction) y un descriptor de forma de grano 3D (la esfericidad verdadera) se calibra primero, utilizando los resultados de la escala de muestras y de la escala de granos de dos pruebas triaxiales en las arenas de Hostun y de Caicos. Luego se valida simulando otras pruebas triaxiales (1) con las mismas arenas, pero en diferentes condiciones (2) con arena de Ottawa, para la que también estaban disponibles imágenes 3D de granos para su examen, y (3) con arena de Ticino, para la cual solo estaban disponibles imágenes 2D de los granos. Finalmente, se presentan resultados de simulaciones DEM a gran escala de la prueba de penetración de cono (CPT), aprovechando el nuevo modelo de contacto propuesto. Los datos experimentales del CPT realizado en una cámara de calibración (CC) sobre arena de Ticino se ajustan con éxito por las curvas de penetración numérica a diferentes presiones y condiciones de confinamiento. Un estudio paramétrico sobre la influencia de la forma de las partículas y la variabilidad de las formas de las partículas puso de manifiesto los efectos fuertemente acoplados de las resistencias rotacional y friccional en los contactos entre partículas. El trabajo descrito en esta tesis facilitará el uso de DEM para simulaciones a gran escala en problemas de ingeniería geotécnica.Postprint (published version

An Empirical Evaluation of Force-Directed Graph Layout

Force-directed graph layout is a widely used algorithm for the automatic layout of graphs. Little experimental work has been done exploring the behaviour of the algorithm under a variety of conditions. This thesis carries out three large-scale metric-based experiments. The first explores how the core algorithm behaves under changes to initial conditions. The second looks at extending the force-directed layout algorithm with additional forces to reduce overlaps. The third develops a novel symmetry metric for graphs and uses that to explore the symmetries of graphs. This thesis also carries out a user study to show that the differences reported by metrics in the graphs are reflected in a difference in user performance when using graphs for a free-form selection task

Fluid Mechanics of Plankton

The cooperation between plankton biologists and fluid dynamists has enhanced our knowledge of life within the plankton communities in ponds, lakes, and seas. This book assembled contributions on plankton–flow interactions, with an emphasis on syntheses and/or predictions. However, a wide range of novel insights, reasonable scenarios, and founded critiques are also considered in this book

Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018

The effect of lithology, sub-bed scale heterogeneities, and mechanical stratigraphy on fault and fracture properties in coal bearing sequences

While sub-surface extraction of coal in the UK has ceased, renewed interest into the internal structure and growth of faults cutting coal measures exists due to applications for mine geothermal projects and analogues for natural gas plays in the Southern North Sea. In this study three field sites are used with detailed field observations, geological mapping, and sedimentological classification undertaken to understand the role lithology and subbed scale heterogeneity plays in the deformation of UK Carboniferous Coal Measure. This study demonstrates, and suggests methods to limit, geologists’ own biases during fracture data collection that can influence the data collected, and hence the derived statistics used for fracture modelling. Biases are also introduced when the temporal evolution and connectivity of individual sets of fault-fracture networks are not considered when assessing connectivity. Unlike binary mechanically layers sequences (e.g. limestone/marl), we find the presence of shale inter-beds and the abundance of sub-bed scale sedimentary heterogeneities (e.g. channel coals) to strongly affect the development fault and fractures. Where jointing exists at the time of faulting, fault-growth was found to be restricted by favourably orientated structures. The thickness and composition of fault-rock is controlled by lithological juxtaposition, with organic fragments found along principle displacement zones of faults of all sizes, even where organic rich layers have apparently not been cut. This study also shows faults that form following the collapse of Pillar and Stall mine workings are strongly affected by mechanical stratigraphy, with the height disruption controlled by a combination of the width of the stall, and the distribution and thickness of competent sandstone layers. Collapse leaves a clay-rich anthropogenic sedimentary layer which will retard the flow of groundwater in abandoned pillar and stall workings. These findings will improve our ability to assess geo-technical risk in ex-coal mining areas and de risk shallow mine geothermal projects.While sub-surface extraction of coal in the UK has ceased, renewed interest into the internal structure and growth of faults cutting coal measures exists due to applications for mine geothermal projects and analogues for natural gas plays in the Southern North Sea. In this study three field sites are used with detailed field observations, geological mapping, and sedimentological classification undertaken to understand the role lithology and subbed scale heterogeneity plays in the deformation of UK Carboniferous Coal Measure. This study demonstrates, and suggests methods to limit, geologists’ own biases during fracture data collection that can influence the data collected, and hence the derived statistics used for fracture modelling. Biases are also introduced when the temporal evolution and connectivity of individual sets of fault-fracture networks are not considered when assessing connectivity. Unlike binary mechanically layers sequences (e.g. limestone/marl), we find the presence of shale inter-beds and the abundance of sub-bed scale sedimentary heterogeneities (e.g. channel coals) to strongly affect the development fault and fractures. Where jointing exists at the time of faulting, fault-growth was found to be restricted by favourably orientated structures. The thickness and composition of fault-rock is controlled by lithological juxtaposition, with organic fragments found along principle displacement zones of faults of all sizes, even where organic rich layers have apparently not been cut. This study also shows faults that form following the collapse of Pillar and Stall mine workings are strongly affected by mechanical stratigraphy, with the height disruption controlled by a combination of the width of the stall, and the distribution and thickness of competent sandstone layers. Collapse leaves a clay-rich anthropogenic sedimentary layer which will retard the flow of groundwater in abandoned pillar and stall workings. These findings will improve our ability to assess geo-technical risk in ex-coal mining areas and de risk shallow mine geothermal projects