Geotechnics

The course aims to provide the student with the basic knowledge of the mechanical behaviour of soils necessary to design geotechnical structures and civil engineering structures/infrastructures interacting with the soil.

The student will acquire the ability to: analyze the multiphase nature and the stress-strain state in a soil deposit; - analyze filtration and consolidation phenomena and their effects on the territory; - interpret the most common laboratory and in-situ tests to determine the geotechnical design parameters.

Genesis and nature of soils. Soil classification and Atterberg limits – Grain size curves. Physical states and index properties. Relative density. Phase relationships. The principle of effective stress. Flow continuity equation. Darcy's law. Coupled and uncoupled problems. Geostatic stress. Skempton parameters.

The steady-state flow of water through the soil. Head and pressure variation in a fluid at rest. Confined and unconfined motions. Solution of 1D problems. Flow parallel to soil layers.  Flow normal to soil layers. Equivalent hydraulic conductivity. Determination of the hydraulic conductivity. Solution of 2D problems. Finite difference method and flow nets. Siphoning. 

The transient flow of water through the soil. Primary consolidation: hydraulic aspects, initial and boundary conditions. Solution of governing consolidation equation. Subsidence. Oedometer test. Determination of the parameters necessary for the study of primary consolidation and its effects in urban and extra-urban areas. Secondary consolidation.

Deformability and shear strength of soils and laboratory tests. Definitions of key terms. Material responses to normal loading and unloading. Material response to shear forces. Elasticity, Plasticity. Soil failure. Critical state theory. Direct shear apparatus. Triaxial apparatus. Stress paths. C-D, C-U and U-U triaxial tests for cohesive and incoherent soils. Strength parameters and deformability parameters. 

Limit equilibrium states and earth pressures. At rest, active and passive earth pressures. Rankine theory. Generalized Rankine theory. Applications to real case histories.

In situ tests. Accessible excavations, surveys, and sampling. CPT, CPTU, SPT, vane test, pressuremeter test, static and dynamic flat plate dilatometer tests, SASW, MASW. Main correlations between the results of in-situ investigations and geotechnical parameters.

Examples of geotechnical design in civil engineering.

Book n. 1 -  Lancellotta, R. (2012). Geotecnica. Zanichelli, Bologna. 

Book n. 2 -  Budhu M. (2010). Soil mechanics and foundations. John Wiley & Sons Inc. USA. 

Book n. 3 - Picarelli L. (2021). Appunti di Geotecnica con 100 esercizi risolti. Hevelius.

Book n. 4 - Tonni, L., Gottardi, G. (2010). Esercizi di geotecnica. Esculapio, Bologna. 

Book n. 5 - Burghignoli A. (2018). Meccanica delle terre. Hevelius.

Book n. 6 - Lancellotta, R., Costanzo, D., Foti, S. (2020). Progettazione geotecnica secondo l’Eurocodice 7 e le Norme Tecniche per le Costruzioni 2018. Hoepli, Milano.  

The written test is designed to verify the student's ability to apply theoretical concepts to solve practical problems. It includes theory questions with true/false answers and exercises. Admission to the oral test is obtained with a written test score of at least 15/30 (maximum score of 30/30). The oral test covers all the topics listed in the program. The final score is determined by averaging the scores obtained in the written and oral tests.

During the course, there are also 3 optional ongoing tests. Each ongoing test consists of several questions that must be answered with true/false. Each ongoing test gives the right to a maximum score of 1 (minimum -0.25) for a maximum total score of 3 points (minimum -0.75). Each in-progress test consists of 5 questions. Each correct question is assigned a score of +0.2, and each incorrect or void question is assigned a score of -0.05. The points scored during the ongoing tests will be added to the average written and oral test scores to achieve the final score. The student who scores at least 2.4 points by adding the various ongoing tests and at least 22 in the written test is exempted from the oral test. If he/she aspires to a higher final score than that obtained by adding the score of the ongoing tests and the score of the written test, he/she will have to take the oral test. The score of the in ongoing tests is valid until May 31, 2026.

- Explain the principle of effective stress. 

- What are the Skempton parameters, and how are they determined?

- How does the behavior of coarse-grained soils differ from that of fine-grained soils?

- How can the consolidation phenomenon be studied, and what are its potential effects on the under-construction or existing structures?

- What are the risks of the siphoning phenomenon?

- How can soil resistance and deformability parameters be determined, and how do they affect the various design choices?

- What is the difference between peak shear angle and constant volume angle?

- Determine the passive and active earth pressure on a retaining wall.

- Explain the SPT test and indicate which geotechnical parameters can be obtained from this test and how.