Ing - Civ (Mag.)(ord. 270) - MI (488) INGEGNERIA CIVILE - CIVIL ENGINEERING
056258 - GEOTECHNICAL MODELLING
055764 - ELEMENTS OF GEOTECHNICAL MODELLING
056203 - GEOTECHNICAL MODELLING 2ND
The course focuses on the principles and the analytical and numerical tools needed to model the behaviour of soils and the response of geotechnical systems under time dependent loads, for engineering applications. Hydro-mechanical, thermo-mechanical and chemo-mechanical coupling are addressed. The role of non-linearity, initial state, and previous stress history is emphasised. Physical modelling is introduced as a complementary tool for the analysis.
Risultati di apprendimento attesi
The aim of course is to develop understanding on how the physical behaviour of soils can be described in mathematical terms accounting for multiphysics coupling, how simple strain hardening elastic-plastic models for the main categories of soils can be developed and implemented, how an appropriate soil model can be chosen, initialised and calibrated to be used in a numerical analysis, what is the role of the ratio between the rate of loading and the rate of response of geotechnical systems, and how geotechnical design and assessment can be tackled by a numerical approach in the design and in the assessment.
At the end of the first module the students will be able to: (i) analyse laboratory data and choose an appropriate model to reproduce the key aspects of the specific soil behaviour; (ii) calibrate and implement a chosen model based on available data; (iii) discern advantages and limitations of specific models to be used in numerical analyses; (iv) properly address initialisation of non-linear models in the analysis of the soil response; (v) evaluate how models can be extended to account for unsaturated and non-isothermal conditions, and different chemical composition of the pore fluid.
At the end of the second module the students will be able to (vi) evaluate the role of loading rate on the response of a geotechnical system; (vii) choose the appropriate set of field equations necessary to solve practical geotechnical problems with emphasis on civil and environmental engineering applications; (viii) design a finite element model for the non-linear analysis of a typical geotechnical design problem; (ix) properly elaborate the results of a numerical analysis and discuss its limitations; (x) evaluate the potential of a numerical analysis for Serviceability Limit States (SLS) and Ultimate Limit States (ULS) compared to simplified analytical solutions.
The contact hours are organised with a combination of lectures and practical sessions. The lectures will introduce the students the main principles of soil modelling, at both the material and the engineering scale.
The topics addressed in the first module include:
Formulation and use of “elastic” models. “True” elasticity and “Pseudo-elasticity”. Linear and non-linear elasticity. Parameter calibration strategies.
Formulation and use of perfect plasticity. Strength envelopes in the stress spaces. The role of plastic deformation. Introduction to the plastic potential.
General formulation of strain-hardening elastic-plastic models for soils. Examples: Modified Cam Clay, Strain hardening Mohr-Coulomb, Nova and Wood.
An introduction to models for natural complex soils
Introduction to unsaturated soils: what’s new compared to saturated states? Three phases, “effective” stresses, enhanced role of fabric. Water retention behaviour and hydraulic conductivity of soils under unsaturated conditions. The mechanical response of unsaturated soils: shear strength and compressibility. Introduction to models accounting for unsaturated conditions: BBM and further developments.
Introduction to the role of the chemical composition of the pore fluid: what’s new compared to distilled water? Miscible and non-miscible contaminants. The role of the chemical composition of the pore fluid on clay fabric: the double layer theory and its limitations. The role of pore fluid chemistry on hydraulic conductivity, shear strength and compressibility. Introduction to models accounting for different pore fluids in the context of strain hardening elasto-plasticity.
The topics addressed in the second module include:
Hydro-mechanical coupling in the geotechnical analysis: beyond Terzaghi 1D consolidation theory. Rate of loading vs. rate of dissipation. Drained and undrained conditions. Time dependent and cyclic loading.
Formulation of the general coupled governing equations, and their finite element discretisation.
Drained, undrained and time dependent coupled analysis: choices, advantages and limitations.
Basics of Finite Element Method for geotechnical applications: geostatic stress; initialisation of stress state and state variables; boundary conditions; non-linear analysis; drained, undrained and fully coupled analysis.
Soil structure interaction: how can we deal with it?
Variable geometry in geotechnical engineering: construction and excavation.
How does the formulation of the coupled problem change for unsaturated conditions? The fully coupled three-phase formulation and a two-phase simplified solution. Boundary and initial conditions.
Applications of unsaturated soils concepts: undisturbed sampling, free surface flow and pumping, rainfall induced landslides.
Introduction to physical modelling principles.
Practical sessions include exercises and applications aimed at introducing the students to the implementation of the previous concept in the geotechnical engineering analysis and assessing the comprehension of the main theoretical background concepts. A series of practical sessions is dedicated to introduce the students the numerical code they will use for part of their homework.
Continuum Mechanics; Soil Mechanics; Basic concepts on the numerical analysis of linear systems.
Modalità di valutazione
Assessment of the learning objectives include formative assessment during the course period and evaluation assessment at the end of the course. During the course the students will get a number of group reports to complete as homework. For those groups who will hand in the reports by the deadlines given in due course, a preliminary assessment and feedback will be given, for them to self-evaluate achievement of the learning objectives and improve any insufficient part. Handing in the assignments in due time during the course is highly recommended, though not compulsory.
All the home assignment reports must be handed in one week before the chosen examination date, the latest, for the final evaluation purpose.
The final evaluation will include the home assignment reports and an oral examination. The written reports will be evaluated for the student capability to bring theoretical knowledge to the solution of practical engineering problems, including the choice of suitable models for different geotechnical applications, the interpretation of the laboratory tests, the choice and the calibration of adequate models for the different soils, the numerical simulation of selected geotechnical systems. The oral examination will start with a discussion on the content of the reports, and aims at assessing achievement of the learning objectives, including the fundamental theory which modelling is built on.
Muir-Wood D., Geotechnical Modelling , Editore: Taylor & Francis, Anno edizione: 2004
Journal / Conference papers on selected topicsuploaded on BeePCourse Notes on selected topicsuploaded on BeePD.M. Potts & L. Zdravkovic, Finite element analysis in geotechnical engineering: theory, Editore: Thomas Telford, London, Anno edizione: 1999
D.M. Potts, L. Zdravkovic, T.I. Addenbrooke, K.G. Higgins & N. Kovacevic, Finite element analysis in geotechnical engineering: application. , Editore: Thomas Telford, London, Anno edizione: 2001
I.M. Smith, D.V. Griffiths & L. Margetts, Programming the finite element method. , Editore: John Wiley & Sons, Chichester, Anno edizione: 2013
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