# Unit information: Design of Geotechnical Structures in 2015/16

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Unit name Design of Geotechnical Structures CENG30005 10 H/6 Teaching Block 1 (weeks 1 - 12) Professor. Ibraim Not open Geotechnics 2 (CENG21200) None Department of Civil Engineering Faculty of Engineering

## Description

To develop students' understanding of the behaviour of earth retaining structures and building foundations.

## Intended learning outcomes

By the end of the course, successful students will

ULO 1. Understand the central place occupied by Limit Equilibrium methods and Modes of Failure in geotechnical design PLO A2

ULO 2. Know about various retaining wall types and be able to analyse typical cases; PLO A2

ULO 3. Be able to size shallow foundations and/or assess their safety; PLO B5

ULO 4. Be able to estimate the settlement of foundations on clays and sands/gravels; PLO B5

ULO 5. Understand time-dependent settlement (consolidation) and the decay of excess pore pressure PLO A2

ULO 6. Understand the mechanisms of load transmission for piled foundations; PLO A2

ULO 7. Be able to assess ultimate pile resistance in various soil types and calculate safe working loads; PLO B5

ULO 8. Know something of pile group behaviour, including settlement. PLO A2

Syllabus

EARTH PRESSURES
Introduction and revision. Drained analysis, Rankine-Bell equation, extended Coulomb wedge analysis, effect of wall friction. Undrained analysis, Rankine and Coulomb. General earth pressure equations (undrained and drained), earth pressure coefficients, effect of water.

EARTH RETAINING STRUCTURES
Typical wall types, Eurocode 7 limit state approach, modes of failure, minimum deformation requirements. Design of gravity walls, including RC stem walls. Design of embedded walls. Cantilever walls, equilibrium and stability, method of analysis. Propped/anchored walls, Free Earth Support Method, effect of wall flexibility, water pressure cases.

FOUNDATIONS
Foundation types, foundation design to Eurocode 7, gross and net pressures.

BEARING CAPACITY
Undrained analysis, effect of shape and depth of foundation, effect of soft clay at depth. Drained analysis, effect of foundation shape, effect of water. Traditional Factor of Safety against bearing capacity failure and EC7 partial factor on shear strength.

SETTLEMENT ANALYSIS
Settlement classification, causes of settlement, immediate and time-dependent settlement. Consolidation, piston and spring analogy, oedometer test results and calculations of 1xD settlement (mv & Cc). Pore pressures in oedometer, degree of consolidation and average degree of consolidation. Terzaghi's 1xD consolidation theory, secondary compression (creep), factors affecting rate of settlement. Elastic stresses beneath loaded areas, stress influence factors (Fadum), validity of elastic theory for real soils. Elastic Displacement Theory, drained and undrained parameters, effect of finite layer thickness (Steinbrenner), effect of depth of embedment, layered soil profile, foundation rigidity, selection of parameters, gross and net pressures. Estimating amount of settlement on clays (1xD and 3xD cases), use of EDT and 1xD method. Settlement on granular soils, in-situ tests, Burland and Burbidge method.

PILED FOUNDATIONS
Reasons for piling, examples of pile types, load-settlement behaviour of single piles, safe working load. Single piles in clay, total stress analysis, adhesion factors (alpha values) for bored piles in stiff clay; effective stress analysis, beta values for driven piles in soft clay. Large diameter under-reamed bored piles, stability and settlement. Negative skin friction. Single piles in sand, conventional approach, cone penetrometer method, long piles. Design of pile groups, comparison of group/single pile behaviour, installation effects, block failure, punching failure, settlement using equivalent raft.

## Teaching details

22 hours of lectures

3 hour revision classes prior to exam

## Assessment Details

100% 2hour examination