Soil Mechanics II

Instance: 2012/2013 - 2S

Cycles of Study/Courses

Last updated on 2013-02-21.

Fields changed: Objectives, Métodos de ensino e atividades de aprendizagem, Fórmula de cálculo da classificação final, Componentes de Avaliação e Ocupação, Programa, Observações, Obtenção de frequência

Teaching language

Objectives

RATIONALE

Continuing from Soil Mechanics 1, the curricular unit Soil Mechanics 2 deals with the concepts, theories and methods used in Civil Engineering for the design of works, structures and structural components whose conception, analysis and construction are significantly conditioned by the  mechanical behaviour of the surrounding soil masses and discusses the methods employed to charcterize this behaviour. This makes Soil Mechanics 2 a fundamental discipline in Civil Engineering.

OBJECTIVES

Introduction to the concepts, theories and methods used in Civil Engineering for the design of works and structures whose stability relies on the mechanical behaviour of soil masses. Introduction to the methods employed for characterizing that behaviour.

Learning outcomes and competences

KNOWLEDGE

Describe the main field tests for characterizing the mechanical behaviour of soils. Identify for each test the advantages and limitations. Understand the theories and methodos for limit equilibrium analysis of geotechnical works: embankments, slopes, retaining walls, shallow and deep foundations. Contact with analyses of deformation applied to settlement of shallow foundations. Make preliminary contact with earth works, in particular with the compaction of landfill material. Make contact with the  methods of geotechnical design.

UNDERSTANDING

Interpret the results of field tests in order to obtain estimates of soil mechanical parameters (strength and stiffness). Explain the effect of time in problems of loading or of excavation of clayey soil masses, in association with the more appropriate options for (short and long term) stability analyses. Explain the phenomena involved in the instabilization of natural slopes. Aprehend the typical strategy for stabilization studies of natural slopes. Discuss the interaction problems between a vertical (or sub-vertical) structural face and the backfill according to their relative motion in order to obtain the corresponding limit interaction force values. Relate them with the magnitude of the strains associated with each case.  Identify the phenomena involved in the foundation interaction with the adjacent soil in failure conditions and in service conditions.  Discuss for service conditions the influence of foundation deformability in the load distribution and settlements, both for isostatic and hyperstatic structures. Take contact with the geotechnical design methods using global or partial safety coefficients, in this case in accordance with Eurocode 7. Take contact with the methods for study of large earth works.

ANALYSIS AND APPLICATION

Select the mechanical characteristics of soils from the results of field tests. Apply the methods of failure analysis of geotechnical works (retaining walls, embankments, slopes, foundations). Use a computer program to analyze the stability of land masses. Apply methods for evaluating settlements of shallow foundations. Design foundations and retaining walls using global or partial safety factors, in this case applying Eurocode 7.

SYNTHESIS

Formulate strategies for natural slope stabilization study and design approaches taking into account the contribution of Engineering Geology. Formulate strategies for foundation design, in combination with site investigation studies and the analysis of the loading from the structure to be built. 

Working method

Pre-requirements (prior knowledge) and co-requirements (common knowledge)

It is essential to have a good background acquired in Soil Mechanics 1.

Program

Overall stability of soil masses. Limit analysis theorems. Lower and upper bound theorems. Limit equilibrium methods. Method of slices. Fellenius and simplified Bishop methods. Application to slopes and embankments on soft clayey soils. Stability of embankments on soft clay soils. Methods for stability improvement: phased construction, lateral berms, foundation strengthening with stone columns, embankment base reinforcement with geosynthetics, use of lightweight aggregates. Excavations in cohesive soils. Short term vs. long term stability of loadings on clay soils. Stabilty of natural slopes. Infinite slope. Wedge method. Stabilization of natural slopes. The role of observation. Lateral earth pressure. Rankine active and passive states. Strains associated with Rankine states. Active and passive thrust. Caquot-Kérisel tables. Coulomb theory. Mononobe-Okabe theory to estimate active and passive pressures under seismic conditions. Design of gravity retaining walls. Bases for the design of geotechnical works. Global and partial safety factors in Geotechnics. Introduction to Eurocode 7 - Geotechnical Design. Undisturbed sampling. In situ testing versus laboratory testing. Penetration tests: SPT, CPTU (piezocone) and dynamic probing. Vane-shear test. Cross-hole seismic test. Plate load test. Pressuremeter tests: Ménard and self-boring pressuremeter. Shallow foundations. Bearing capacity. Theoretical solution and correction factors. Immediate settlement. Elastic solution and semi-empirical corrections. Schmertmann method. Criteria for estimating the soil deformability modulus. Allowable settlement. Soil-structure interaction. Introduction to pile foundations. Bearing capacity of vertically loaded piles: classical method and empirical method based on the results of CPT or DMT tests. Compaction. Basic concepts, tests and compaction equipment. Introduction to the design and construction of large embankment works.

Mandatory literature

Teaching methods and learning activities

Lectures for the presentation of the concepts, principles and theories with reference to works, accidents and natural phenomena conditioned by the behaviour of soil masses. Tutorials for the resolution of numerical applications from the proposed problem sheets. Use of a computer program for slope stability analysis. Lab classes for the observation and/or presentation of lab and field tests and processing of test results. Field trips.

Evaluation Type

Amount of time allocated to each course unit

Eligibility for exams

“Achieving final classification requires compliance with attendance at the course unit. It is considered that students meet the attendance requirements if, having been regularly enrolled, the number of absences of 25% for each of the classes’ types is not exceeded. The following cases are exempted from the attendance requirements: i) cases prescribed by law, including student workers; ii) students who were admitted to exams in the previous academic year.”

Calculation formula of final grade

The final grade is based on the results of two (optional) tests and three (optional) practical assignments, made in practical classes during the semester, plus the final exam. The final grade, CF (on a 0 to 20 scale) is obtained as CF = max{CT ; EF} where CT = 0.07 x CAD1 + 0.10 x CAD2 + 0.04 x CAD3 + 0.02 x CAD4 + 0.02 x CAD5 + 0.75 x EF (CAD1 – marks of test 1; CAD2 – marks of test 2; CAD3 – marks of assignment 1; CAD4 – marks of assignment 2;CAD5 – marks of assignment 3; EF – marks of final exam). 

NOTE 1: The tests and ssignments associated to the marks CAD1 to CAD5 are optional. In case the student misses any of them the corresponding weight is added to that of the final exam.

NOTE 2: All students enrolled in the course are classified according to this method.

NOTE 3: For students who have missed all five the optional tests and assignments or who have obtained on them a grade below 10, the final grade will be that of the final exam.

NOTE 4: Students who wish to obtain a final grade over 17 must have at least 17,5 in the final exam and apply for an oral exam.

Observations

SPECIAL RULES FOR MOBILITY STUDENTS In exams, tests and assignments students may use one of the following languages: Portuguese, English, Spanish, French or Italian.

ESTIMATED STUDY TIME OUT OF CLASS: 3 hours per week.