Micromechanisms of inelastic deformation in sandstones: An insight using x-ray micro-tomography

This study investigates the grain-scale mechanisms that lead to failure by strain localisation in specimens of Fontainebleau sandstone with different degrees of cementation. While the effects of inter-particle bonding on the mechanical behaviour of granular geomaterials, including soft rocks, have been largely studied, the physical micro-scale mechanisms governing the material deformation are still poorly understood. In this study, laboratory techniques have been developed to allow a non-invasive investigation of the internal deformation of sandstones during triaxial compression to failure. The material investigated was Fontainebleau sandstone, a quartzite formation from the Paris basin (France), which can be found as very hard, tightly cemented sandstone or more porous and less cemented material. Specimens with porosities of 6 and 21% were investigated. Triaxial compression tests at confining pressures of 2 and 7 MPa were conducted on dry cylindrical specimens of 11 mm diameter and 22 mm height. Three-dimensional (3D) images of the full specimens were obtained by carrying out x-ray micro-tomography scans at key points throughout the test. The high-resolution 3D tomographic images have a voxel size of 8.5 μm (0.033d50), allowing clear identification of the grains. This analysis suggests that dilatancy of the material, which depends on the degree of bonding between grains, plays a fundamental role in the failure mode of granular media. Insights into bonding rupture mechanisms and grain damage by inter- and intra-granular cracking are presented

An experimental study of micro-scale deformation in a soft sandstone

This study investigates the grain scale mechanisms that lead to failure by strain localisation in a slightly cemented sandstone. While the effects of interparticle bonding on the mechanical behaviour of granular geomaterials, including soft rocks, have been largely studied, the physical micro-scale mechanisms governing the material deformation are still poorly understood. In this study, laboratory techniques have been developed to allow a non-invasive investigation of the internal deformation of a soft sandstone during triaxial compression to failure. The material studied is Fontainebleau sandstone, a quartzite formation from the Paris Basin, with a porosity of 21 %. Fontainebleau sandstone is a uniformly graded material with a mean grain size of 260 m. Triaxial compression tests at confining pressures of 2 MPa and 7 MPa were conducted on dry cylindrical specimens of 11 mm diameter by 22 mm height. Three-dimensional images of the full specimen were obtained by carrying out x-ray micro-tomography scans at key points throughout the test. The high-resolution tomographic images have a voxel size of 8.5 m (0.033d50) allowing a clear identification of the grains. A preliminary analysis has suggested that the failure mechanisms can be different for the samples tested at different confining pressures, which has a direct implication on the permeability of the material

Numerical simulation of the heat penetration in two-plate arc welding

A mathematical model and numerical simulation of the three-dimensional and transient metal arc-welding process is presented. The heat source is considered as spatially distributed following a centered Gaussian bell, while the substract material (Al 6063) is assumed homogeneous and isotropic with temperature-dependent thermal properties. Radiation and convection are also calculated through an empirical temperature dependent correlation. Phase-change phenomenon is included as a discontinuity in the material specific heat. Calculations were performed by using a finite volume code (CFX4.2TM). Computed heat penetration and weld metal area are found to be in good agreement with experimental data

Numerical simulation of the heat penetration in two-plate arc welding

A mathematical model and numerical simulation of the three-dimensional and transient metal arc-welding process is presented. The heat source is considered as spatially distributed following a centered Gaussian bell, while the substract material (Al 6063) is assumed homogeneous and isotropic with temperature-dependent thermal properties. Radiation and convection are also calculated through an empirical temperature dependent correlation. Phase-change phenomenon is included as a discontinuity in the material specific heat. Calculations were performed by using a finite volume code (CFX4.2TM). Computed heat penetration and weld metal area are found to be in good agreement with experimental data

Microstructure evolution on sandstones with different degrees of cementation

This study investigates the grain scale mechanisms that lead to failure by strain localisation in specimens of Fontainebleau sandstone with different degrees of cementation. While the effects of inter-particle bonding on the mechanical behaviour of granular geomaterials, including soft rocks, have been largely studied, the physical micro-scale mechanisms governing the material deformation are still poorly understood. In this study, laboratory techniques have been developed to allow a non-invasive investigation of the internal deformation of sandstones during triaxial compression to failure. The material investigated was Fontainebleau sandstone, a quartzite formation from the Paris Basin (France) which can be found as very hard, tightly cemented sandstone or more permeable and less cemented material. Specimens with porosities 6% and 21% were investigated. Triaxial compression tests at confining pressures of 2MPa and 7MPa were conducted on dry cylindrical specimens of 11mm diameter by 22mm height. Three-dimensional images of the full specimen were obtained by carrying out x-ray micro-tomography scans at key points throughout the test. The high-resolution tomographic images have a voxel size of 8.5um (0.033d50) allowing a clear identification of the grains. The analysis suggests that dilatancy of the material which depends on the degree of bonding between grains, plays a fundamental role on the failure mode of the granular media

A microstructural finite element analysis of cement damage on Fontainebleau Sandstone

This paper presents a numerical simulation that uses tomographic data to reproduce the grain-scale mechanisms taking place during deformation of Fontainebleau sandstone. Previous investigation using x-ray tomographic images acquired during triaxial compression has highlighted the role of bonding rupture mechanisms in the failure mode of the material. The model the deformation of the sandstone, images of the internal topology were used to generate an image-based finite element mesh and the grain-scale phenomena such as, the opening and propagation of the cracks associated with the debonding of the cemented grains, were reproduced using a simple constitutive model

SASICE: Safety and sustainability in civil engineering

The performance of the built environment and the construction sector are of major importance in Europe’s long term goals of sustainable development in a changing climate. At the same time, the quality of life of all European citizens needs to be improved and the safety of the built environment with respect to man-made and natural hazards, such as flooding and earthquakes, needs to be ensured. Education has a central role to play in the transformation of a construction sector required to meet increasing demands with regard to safety and sustainability. In this work, the SASICE project is presented. The aim of this project is to promote the integration of safety and sustainability in civil engineering education. The project is organised in the context of the Lifelong Learning Programme, funded by the European Community. The coordinator organisation is the University of Bologna. Nine partner universities from different countries are involved in this transnational project. The universities participating to the project constitute a network of high level competences in the civil engineering area, with several opportunities to improve lifelong learning adopting different media: joint curricula, teaching modules and professor and student exchanges. As a response to the challenge regarding new educational methods in sustainable engineering, teaching modules are developed in 4 thematic areas: (1) Safety in construction, (2) Risk induced by Natural Hazards Assessment, (3) Sustainability in construction, and (4) Sustainability at the territorial level. The development of the teaching modules is based on an extensive analysis of the need for highly qualified education on Safety and Sustainability involving all relevant stakeholders (European and national authorities, companies, research institutes, professional organizations, and universities).The main target is enabling students to introduce these advanced topics in their study plans and curricula and reach, at the end of their studies, a specific skill and expertise in safety and sustainability in Civil Engineering. With our natural resources fading away and our infrastructure in dire need of repair, new trends and challenges in civil engineering education in the concept of “Sustainable Development” are needed to be adressed.<br/

(Un)healthy prison masculinities : theorising men's health in prison

This thesis explores the interconnections between masculinity, health and prison. It contests reductionist, individualist and biomedical approaches to health care management in prisons and challenges gender-blindness within criminology and social science where masculinities have been overlooked as key factors of prison culture and organisation. The research set out to explore how masculinities manifest at institutional, social and cultural levels in prison as key determinants of health. The study was conducted in an enhanced wing of an adult male training prison in Southern England. A reflexive ethnographic approach was used, comprising sustained (non-participant)observation, focus group interviewing, and in-depth, semi-structured interviews with thirty-five inmates and four prison officers. The research revealed how prison masculinities were produced and performed by inmates and prison staff, and through the discourses and practices of the prison regime. They were manifested at social and organisational levels as key determinants of health – as ‘deprivations’ associated with imprisonment and as ‘importation factors’ reflecting inmates pre-prison health status. Values of the institution and those of inmates and staff combined to create a pervasively ‘masculine’ atmosphere and culture, which adversely affected the physical and mental health of many prisoners. This thesis recommends that health policy for prisons is developed and organised with consideration to issues of gender and power. The masculine ideology that underpinned the organisational and social fabric of the prison in this study was evident in the attitudes and behaviours of inmates and staff and in the ‘progressive regime’ advocated by the Prison Service. This research shows that a broad, holistic and ‘gendered’ view of prison health can provide alternative insight into men’s health in prisons, and therefore offer a positive and productive way forward for future prison health policy, in line with the World Health Organisation’s Healthy Prisons philosophy.EThOS - Electronic Theses Online ServiceGBUnited Kingdo