Triaxial tests on frozen ground: formulation and modelling

Artificial Ground Freezing (AGF) is a controllable process that can be used by engineers to stabilise temporarily the ground, provide structural support and/or exclude groundwater from an excavation until construction of the final lining provides permanent stability and water tightness. In this work, the process of ground freezing is studied using a constitutive model that encompasses frozen and unfrozen behaviour within a unified effective-stress-based framework and employs a combination of ice pressure, liquid water pressure and total stress as state variables. The parameters of the constitutive model are calibrated against experimental data obtained from samples retrieved during construction of Napoli underground, in which AGF was extensively used to excavate in granular soils and weak fractured rock below the ground water table

Breakage mechanisms of highly porous particles in 1D compression revealed by X-ray tomography

Grain breakage affects a number of geotechnical engineering problems. In this research study, the breakage of an artificial, porous granular material (light-expanded clay aggregate (LECA)) has been studied in one-dimensional compression with both standard laboratory techniques and in situ X-ray tomography during loading. X-ray tomography has revealed that there is a wide distribution of internal porosity among LECA particles, and particle tracking has been used, for the first time, to give an objective measurement of each particle's life expectancy. Links between micro- and macro-scale quantities are discussed. </jats:p

A healthy prison strategy for HMP Bristol

This report summarises progress in establishing a Healthy Prison strategy for HMP Bristol. It follows a period of consultancy with the prison commissioned by NHS Bristol, and carried out as follow-up to a 2007-8 Health Needs Assessment (HNA) conducted at the prison. The aims of this work were to: [1] assess and build commitment within the prison for a ‘healthy prison’ strategy; [2] produce a realistic and feasible plan for developing the strategy; [3] create a strategy group to lead and drive the project; and [4] form and publish key performance standards for the prison. A period of consultation preceded publication of this report, which involved interviews and meetings with a range of Prison Service and NHS stakeholders and close scrutiny of relevant reports and publications. It should be noted that work on this strategy is ongoing and now forms part of the core business of HMP Bristol

Timelapse ultrasonic tomography for measuring damage localization in geomechanics laboratory tests.

Variation of mechanical properties in materials can be detected non-destructively using ultrasonic measurements. In particular, changes in elastic wave velocity can occur due to damage, i.e., micro-cracking and particles debonding. Here the challenge of characterizing damage in geomaterials, i.e., rocks and soils, is addressed. Geomaterials are naturally heterogeneous media in which the deformation can localize, so that few measurements of acoustic velocity across the sample are not sufficient to capture the heterogeneities. Therefore, an ultrasonic tomography procedure has been implemented to map the spatial and temporal variations in propagation velocity, which provides information on the damage process. Moreover, double beamforming has been successfully applied to identify and isolate multiple arrivals that are caused by strong heterogeneities (natural or induced by the deformation process). The applicability of the developed experimental technique to laboratory geomechanics testing is illustrated using data acquired on a sample of natural rock before and after being deformed under triaxial compression. The approach is then validated and extended to time-lapse monitoring using data acquired during plane strain compression of a sample including a well defined layer with different mechanical properties than the matrix

Matemática e/na/ou etnomatemática?

Este artigo, baseado em uma pesquisa de doutorado, tem como objetivo discutir a concepção de matemática eseus desdobramentos em termos de metodologias de pesquisa no trabalho de cinco proeminentes pesquisadores em etnomatemática, a dizer, Bill Barton (University of Auckland, Nova Zelândia), Eduardo Sebastiani Ferreira (Universidade Estadual de Campinas, Brasil), Gelsa Knijnik (Universidade do Vale do RioSinos, Brasil), Paulus Gerdes (Universidade Eduardo Mondlane, Moçambique) e Ubiratan D’Ambrosio(Universidade Bandeirante de São Paulo, Brasil). A pesquisa foi realizada de uma perspectiva fenomenológica cuja metodologia envolveu uma entrevista com cada um desses pesquisadores, que foram transcritas e analisadas hermeneuticamente. Em seguida, por meio de um movimento de redução fenomenológica, buscamos constituir grandes categorias temáticas, dentre elas, a apresentada neste artigo, que fala da presença da matemática na etnomatemática

Timelapse ultrasonic tomography for measuring damage localization in geomechanics laboratory tests.

Variation of mechanical properties in materials can be detected non-destructively using ultrasonic measurements. In particular, changes in elastic wave velocity can occur due to damage, i.e., micro-cracking and particles debonding. Here the challenge of characterizing damage in geomaterials, i.e., rocks and soils, is addressed. Geomaterials are naturally heterogeneous media in which the deformation can localize, so that few measurements of acoustic velocity across the sample are not sufficient to capture the heterogeneities. Therefore, an ultrasonic tomography procedure has been implemented to map the spatial and temporal variations in propagation velocity, which provides information on the damage process. Moreover, double beamforming has been successfully applied to identify and isolate multiple arrivals that are caused by strong heterogeneities (natural or induced by the deformation process). The applicability of the developed experimental technique to laboratory geomechanics testing is illustrated using data acquired on a sample of natural rock before and after being deformed under triaxial compression. The approach is then validated and extended to time-lapse monitoring using data acquired during plane strain compression of a sample including a well defined layer with different mechanical properties than the matrix

An update on the Tower of Pisa

The Leaning Tower of Pisa has been stabilised in the years 1999–2000 by an International Committee appointed by the Italian Government. An analysis of the whole history of the monument, starting from its construction in the XII century and including the results of the modern monitoring of XIX and XX century led the Committee to the conclusion that the Tower is affected by a phenomenon of instability of the equilibrium, depending on the deformability and not on the strength of the foundation soils. The stabilisation intervention, totally respectful of the integrity of the monument, consisted in slightly decreasing the inclination of the Tower by underexcavating a small volume of soil beneath the north side of the foundation. The paper briefly reports the analysis and the intervention; the observation of the behaviour in the twenty years elapsed since then allows some preliminary evaluation of the future behaviour