1007894 - MECCANICA E DINAMICA DELLE TERRE

The course aims to provide advanced knowledge on the static and dynamic behaviour of soils, necessary for using the main design software. The main constitutive models implemented and implementable in FEM, FDM, etc. numerical codes are illustrated. Advanced static and dynamic laboratory tests are discussed. The following other topics are dealt with: propagation of waves in the subsoil, modification of the seismic signal from the bedrock to the ground surface; modification of the seismic signal due to the foundation-soil kinematic interaction; influence of the deformability and dissipative capacity of the foundation-soil system on the inertial response of the structure; dynamic liquefaction phenomenon.

Frontal lessons through PowerPoint presentations. Workshop in collaboration with geotechnical companies and/or engineers, teachers from other national and international universities. Tests in the classroom. 

A technical visit to a construction site in Sicily is planned to increase the student's knowledge of the topics discussed in the classroom and bring the student closer to the world of work and practice.

Attendance at lessons is strongly recommended, as it is consistent with the learning objectives, which aim to encourage a gradual learning, the active participation of the student in the classroom, and a dialogue between teachers and students.

1. INTRODUCTION

2. SOIL MECHANICS
Set of equations for solving any geotechnical problems in static and dynamic conditions. Laboratory tests in static conditions and evaluation of the main parameters to be used in the most important constitutive models. Failure criteria.Traditional and advanced constitutive models for numerical analyses in static conditions. Static liquefaction.

3. SOIL DYNAMICS
Seismic motion. Local site response. Seismic microzonation. Laboratory tests in dynamic conditions. Traditional and advanced constitutive models for numerical analyses in dynamic conditions. Dynamic liquefaction.

D. Muir Wood (2004). “Geotechnical modelling”. E & FN Spon.

Verification of learning of the course contents will take place through:

1) Ongoing tests, by short individual oral questions and for which a short answer is required. These tests will take place in the classroom in the presence of all students at the end of each "macro-topic". A score will be assigned to these tests, which will be counted at the end of the learning verification process.

2) A final oral exam.

N.B .: It is compulsory to book the oral exam you intend to take; the reservation must be made exclusively through the student portal of the University of Catania website, within the foreseen period. Participation in the ongoing tests (Point N.1) is not compulsory, but strongly recommended.

Illustrate the equation of continuity.

Why do we write the stress-strain law by writing the stresses and strains in incremental terms except in the case of elastic-linear law?

What does the Principle of Effective Stress say?

Is it more appropriate to perform controlled strain laboratory tests or controlled stress laboratory tests?

Describe the biaxial test.

Describe the simple shear test.

What is the difference between the true triaxial apparatus and the conventional triaxial apparatus?

By which apparatus are the shear bands studied? What does a shear band represent?

What is the best apparatus to evaluate the strength of a soil to large strains?

Does the ground offer the same strength  to compression and extension?

If a soil is subjected to an extension test, does the soil go into traction?

What kind of consolidation do I have when I use the oedometric apparatus: isotropic or ko?

Can medium-dense sands go into static liquefaction?

Does the stress path of a SC clay start from a swelling line or from the normal consolidation line?

Is the critical state unique for NC and SC clays?

Illustrate the critical state boundary.

Which soils can exhibit dilatant behavior?

Are Roscoe's surface and Hvorsler's surface detached from each other?

What is the cubic (or volumetric) compressibility modulus and how is it related to Young's modulus

and the Poission ratio?

What is the expression of the elastic stiffness matrix in the axial-symmetry conditions typical of the ordinary triaxial test?

What does the slope of the deviatoric stress-axial strain curve that is obtained by a conventional triaxial test represent?

What are the basic elements to create an elasto-plastic constitutive model?

What figure do we get in the principal stress space by the Mohr-Coulomb failure criterion?

From a mathematical point of view, is the Mohr-Coulomb or Drucker-Prager failure criterion better?

What does it mean that a constitutive model has an associated flow law?

What are the Gauss points for?

Of which matrices is the matrix [C] linear combination by the Rayleigh approach?

Does the Cam-Clay model predict a linear or non-linear elastic phase behavior?

What can happen to the yield surface of the Cam-Clay model?

In the case of simulating the behavior of normalconsolidated clays, once the yield threshold is reached, does the yield surface of the Cam-Clay model remain fixed, does it expand or contract?

What is the difference between seismic risk and seismic hazard?

Tell me three phenomena depending on a seismic event, which can affect the soil.

What are the volume waves? What are the volume waves that arrive first?

What is the difference between the Mercalli scale and the Richter scale?

What are the main laboratory tests with which we study the dynamic behavior of soils?

Illustrate a resonant column test.

As the strain level increases, what happens to the shear modulus and the damping ratio?

Does the elastic threshold (elastic range) separate the linear visco-elastic behavior from the non-linear visco-elastic behavior or does it separate the non-linear visco-elastic behavior from the elastic-plastic one?

In an undrained test, what happens to the pore pressure exceeding the volumetric threshold?

For earthquakes of medium magnitude G and D remain constant or do they vary with the strain level, or do they vary with the strain level and with the number of cycles?

Does the value of the soil damping ratio affect the response of a structure resting on that soil? That is, if we decrease or increase the damping ratio of a soil, the response of the aboveground-structure remains the same or does it change and how?

Is the behavior stable hysteretic or unstable hysteretic for strain levels between the elastic and volumetric thresholds?

What is the reduction that G undergoes at the elastic threshold?

What is the first natural frequency of a homogeneous soil deposit?

What does the transfer function represent in a local seismic response study of a soil deposit?

How does the amplification function change as the soil damping ratio increases?

What is the difference between the amplification function of a soil deposit without damping and the amplification function of the same deposit taking into account the damping of the soil?

How do the shape functions change between the case of soil with a constant shear wave velocity throughout the depth of the deposit and the case of soil with shear wave velocity increasing with depth?

What numerical techniques are there for the study of the local seismic response of a stratified soil deposit?

As the maximum acceleration of a seismic event increases (thought then applied to the bedrock of a soil deposit), taking into account the G-gamma and D-gamma laws, what possible amax (z) trends can we have?

If we have to design a structure in the hills, does the 1D approach continue to be valid?

Can we have amplification functions with ordinates less than 1? If the answer is YES, when?

What kind of hardening is the Severn-Trent model characterized?

Is the Severn-Trent model suitable for loose sands or dense sands or both?

Does the Severn-Trent model have an associated or unassociated flow law?

How many parameters are there in the Severn-Trent model and how are they to be determined?

What is the essential aspect of a hypoplastic constitutive model?

What shape does the dynamic yield surface have in the model by di Prisco et al. (2003)?

What is the difference between the constitutive model of Nova and Montrasio (1991) and that one of di Prisco et al. (2003)?

Why does a soil go into dynamic liquefaction and which types of soil can go into dynamic liquefaction?

How does the seismic history of a site affect its propensity for liquefaction?

Why do we investigate the phenomenon of liquefaction up to about 20 m from the ground level?

What can be the consequences of a dynamic liquefaction on a territory?

What is the expected acceleration threshold below which according to the NTC, 2018 it is not necessary to carry out a site liquefaction study?

What is the maximum depth, starting from the p.c., within which to investigate the phenomenon of liquefaction according to the NTC, 2018?

On what quantities are the empirical criteria based to evaluate the propensity of a site to dynamic liquefaction?

In simplified methods, what is the liquefaction safety factor?

In the method of Idriss & Boulanger (2006) is the magnitude of the earthquake taken into account to evaluate the resistance to liquefaction?

To apply the method of Robertson & Wride (1997) which in situ test must be performed?

What techniques do you know to reduce the propensity of a site to go into dynamic liquefaction?