GEOTECHNICAL NUMERICAL MODELLING
Due to the user-friendliness of commercial software and the increased computational power of computers, geotechnical numerical modelling is a design tool nowadays used even by small consultancies. A proficient use requires good knowledge of constitutive models commonly used for simulating the non-linear behaviour of soils. Furthermore, initial and boundary conditions should be properly set, and the analysis of calculation output require specific skills not provided by basic courses.
The course is concerned with the modelling of geotechnical engineering problems. To begin with, suitable non-linear constitutive models for soils will be presented. Hence, modelling techniques of boundary value problems will be addressed, with particular focus on application to shallow and deep foundations, deep excavations, artificial earth works and natural slopes. The Finite Element method will be used, which is the most common method used for the resolution of the differential equations involved in the geotechnical problem. Depending on the case analysed and the nature of soils involved, the most suitable constitutive model will be chosen, and its input parameters identified based on in situ and laboratory test results. The successful student will acquire competence and skills useful for their future professional career.
AIMS AND LEARNING OUTCOMES
The student will be provided the basic knowledge needed to understand the behaviour of constitutive models commonly used for the modelling of geotechnical engineering problems. Furthermore, the student should be able to autonomously identify the input parameters from in situ and laboratory test results. With that purpose in mind, the theory of plasticity and elastoplasticity will be addressed. The common ancestor of several families of constitutive models, i.e. Cam Clay model, will be covered within the course.
The aim is to make the student an independent user in defining geometry, materials, initial and boundary conditions and calculation phases of a Finite Element model. Hence, after calculating the model, the analysis of the output becomes a crucial step in assessing the correctness of the calculation, and the successful student should be able to gather the most relevant information for the specific needs of the project.
The general knowledge acquired will enable the future professional to make proficient use of any commercial Finite Element software in the market, rather than becoming a specialist on a given commercial package.
The topics covered in Geotechnics course, with particular reference to mechanical behaviour of loose and dense soils, and typical results of oedometer and triaxial tests.
Mainly offline teaching material.
In the first part of the course, which covers the theoretical part, the basic formulation of the Finite Element method for the approximate solution of the equations of geotechnical problem will be addressed. Hence, perfect plasticity and elastoplasticity will be introduced, presenting the constitutive model Cam Clay and its subsequent modifications which led to the modern constitutive models used in geotechnical numerical modelling.
In the second half, several classes of geotechnical engineering problems will be analysed during hands-on tutorials using the Finite Element software PLAXIS 2D. Amongst which, examples of calculations of shallow and deep foundations, deep excavations in urban environment, man-mad earth works (embankments) and natural slopes. Depending on the case, numerical analysis will be used for evaluating safety or short/long term settlement.
The slides of the lectures will be provided through Aulaweb service. Further reading on the matter can be found in the following references:
- Wood (1990): Soil behavior and Critical state soil mechanics
- Potts & Zdravkovic (1999): Finite element analysis in geotechnical engineering: Theory
- Potts & Zdravkovic (2001): Finite element analysis in geotechnical engineering: Application
- Potts, Axelsson, Grande, Schweiger & Long (2002): Guidelines for the use of advanced numerical analysis
Ricevimento: Available upon request.
MARTINO LEONI (President)
RICCARDO BERARDI (President Substitute)
Mainly offline teaching material.
The exam can be taken as written (multiple choice quiz) or oral, depending on the student's choice.
It will be assessed the ability to anticipate the soil model response when applied to typical stress path normally encountered in Geotechnical Engineering problems. The evaluation will be based on quality of exposition, correct use of technical terms and ability of applying the newly acquired knowledge in becoming autonomous users of modelling tools, thus easily moving from input data definition to the critical analysis of the calculation output.