JM Head, MSc, CEng, MIMM, FGS, and CP WYNNE, MSc, DIC, FGS. This paper was first published in GE’s April 1985 edition.
The design of retaining walls is complex and has always posed problems for geotechnical and structural engineers. To test current standards of design practice, a “Design Challenge” was set in the May/June edition of CIRIA News (1984). The results were surprising. Analysis of the submissions to the challenge identified a number of recurrent design difficulties and uncertainties, the most important of which are:
- The choice of an appropriate and rational design method and application of realistic safety factors.
- Application of earth pressure coefficients, particularly when dealing with wall friction and groundwater pressures.
- Understanding the implications of the “fixed earth” and “free earth” assumptions.
- Confidence; 45% of the entrants stated that they did not believe their answers or aspects of their calculations.
The eleven respondents represented a wide cross-section of organisations involved with design. Six of the eleven were aged over thirty. The difficulties that these engineers encountered are felt to be typical of the problems experienced by most practising engineers.