Computing for Geotechnical Design:Equilibrium, Strength, Strain, Dilation and Superposition 

Some basic principles of mechanics were reviewed, using examples to show how they are important to practical design. Equilibrium is the fundamental requirement of many engineering calculations, and it is important to ensure that all forces can be transmitted into the ground that is able to resist them; computer programs that consider only part of the equilibrium may be insufficient. Modern finite element programs are easy to use, but it is essential that users cling to a sound grasp of soil mechanics and behaviour, and constantly ask themselves if the model in use is suitable for the current task; in particular dilation is important in controlling the strength of undrained or confined soils. Engineering courses tend to concentrate on stress states and stress analysis, but strain is much easier to observe and sometimes gives important warnings of impending problems. Finally, the principle of superposition was carefully taught, with emphasis that it only applies in linear situations; but in practice, this limitation is often forgotten.

Arup Fellow,  Honorary Professor at the University of Nottingham

Dr Brian Simpson is an Arup Fellow, a principal of Arup Geotechnics and an Honorary Professor at the University of Nottingham, UK.  He has worked on a wide range of geotechnical and ground-structure interaction problems, maintaining particular interests in numerical modelling, retaining structures and tunnels.  He presented the BGA Rankine Lecture in 1992and a State-of-the-Art report on Geotechnical Analysis and Design at the 2009international conference of ISSMGE. Since the early 1980’s, he has been involved in the development of Eurocode 7 (Geotechnical Design), having been a member of its drafting panels and vice-chairman of the CEN (Comité Européen de Normalisation) committee on Eurocode 7 (SC7).  He has authored two commentaries on Eurocode 7 and several papers on various related issues.  He is the current chair of ISSMGE Technical Committee TC205 on Safety and serviceability in geotechnical engineering and of the BSI committee on geotechnical codes, B/526. He is often the UK delegate to SC7 and is a member of several of the “Evolution Groups” set up to propose further developments of Eurocode 7.