Ελληνικά

Selected Topics in Foundation Engineering

Course Description:

  • Flexible retaining walls and anchors: General overview. Computation of earth pressures for cohesive and cohesionless soils, under various drainage and flow conditions. Design of self supported flexible walls (without anchors). Design of flexible walls with a single anchor at the top or multiple anchors along the height. Construction and design methods for anchors. Evaluation of the overall stability of the wall-anchor-soil system. Computer aided application in design practice.
  • Soil improvement and reinforcement: General review of available methods. Soil improvement by pre-loading. Strength and compressibility of the improved ground for different cases of applied preloading. Design of drains to accelerate excess pore pressure dissipation and reduce the required preloading period. Soil reinforcement using gravel piles. Construction methods. Bearing capacity and settlements of single gravel piles and groups of gravel piles. Shear strength parameters of "equivalent uniform" of gravel pile improved soil layers. o Field exercises: Visits of relevant construction sites within the Greater Athens area and a (2-3 day) trip to major construction sites all over Greece.
  • Semester 9
  • Teaching hours 4

Prerequisite Knowledge

Soil Mechanics (Ι & ΙΙ) and Foundations

Course Units

# Title Description Hours
1 Introduction The presentation of the contents and the objectives of the course follows a brief selective review of the basic knowledge required for the teaching of individual subjects. In particular, emphasis is given to the theory of earth pressures under drained and undrained (from Soil Mechanics I), steady state water flow through the pores, as well as permanent water flow and soil consolidation theory (from Soil Mechanics II) 2Χ4=8
2 Flexible Retaining Structures The theory of earth pressure computattion is applied to the case of flexible retaining walls without anchors (cantilevers) as well as with a single anchor or multiple anchors. The cases of retaining walls in sand and in clay are examined separately, with emphasis on undrained (short term) and drained (long term) stability issues. 4Χ4=16
3 Anchors The practice of anchor construction is initially presented practice, and the design methodology follows. The following failure modes are considered: anchor pullout, wedge failure, global slope stability failure and composite failure Kranz. 2Χ4=8
4 Ground Improvement & Reinforcement The different ground improvement and reinforcement methods applied in practice are initially reviewed. In the sequel teaching focusses upon three of these methods which are most common in geotechnical construction: (a) Pre-loading of weak clay deposits to increase the bearing capacity and reduce settlements, (b) Use of drains to accelerate the excess pore water pressure dissipation and reduce the required preloading time, and (c) Use of gravel piles, combined with vibro-compaction or vibro-floatation, in order to increase the shear strength and reduce the compressibility of weak soil layers bearing surface foundations and embankments. 5Χ4=20

Learning Objectives

Successful completion of the course requirements will enable students design and supervise construction of:

  1. Flexible retaining walls for deep excavations,
  2. Anchors for the support of flexible retaining walls rock slopes,
  3. Preloading works for clayey soils,
  4. Plastic and sand drain networks
  5. Group of gravel piles for the enhanced foundation stability and settlement of buildings, embankments, etc.

Teaching Methods

Teaching methods Classroom lectures, where the presentation of theory is followed by the representative problem solving. Visit to construction sites for special foundation systems and geotechnical works, relevant to the course objectives, inside and outside the greater Athens area.
Teaching media Use of the black-board to prove theoretical relationships, solve numerical examples, etc.! Use of Power Point presentations and videos for the illustration of construction methodologies and field applications.
Computer and software use Computer aided "term project" related to the design of deep excavations and flexible retaining walls (software REWARD and PLAXIS).
Problems - Applications Homework for solution (at home) and presentation to the class from interested students. This homework is optional and not rated. On the contrary the students are rated for problem solving in the class (two midterm exams)
Assignments (projects, reports) Computer aided "term project" related to the design of deep excavations and flexible retaining walls (software REWARD and PLAXIS). The project is run by groups of 2-4 students, who are responsible for delivering brief technical report (up to 10 pages) and undergo an oral examination.

Student Assessment

  • Final written exam: 50%
  • Mid-term exam: 30%
  • Assignments (projects, reports): 20%

Textbooks - Bibliography

  1. Class notes by G. Bouckovalas (posted at the Internet)
  2. Braja M. Das (1998). Principles of Foundation Engineering, PWS Publishing, ITP.
  3. Rodringo Salgado (2008). The Engineering of Foundations, Mc Graw Hill, ...
  4. S. Kostopoulos. Geotechnical Works - Analysis of Design and Construction Methods (Volume Ι and ΙΙ, in Greek)