The design of stiff in situ walls retaining overconsolidated clay. Part 1: Short term behaviour. Part 2: Long term behaviour

In urban areas of the United Kingdom increased use is being made of embedded retaining walls both for new road construction and road improvements. Many of the urban areas in the UK are founded on deposits of stiff, overconsolidated clays of high plasticity which present difficulties for the design of geotechnical structures. A programme of research into the behaviour of embedded walls in stiff clay is being carried out by the Transport and Road Research Laboratory, aimed at improved methods of design. A method is set out by which designers can check both the safety and serviceability of relatively stiff reinforced concrete retaining walls constructed in-situ in overconsolidated clay. The first calculation is of the mean soil strength which must be mobilised for equilibrium. Shear stress-strain data are then used to deduce the characteristic shear strain. This is then distributed between the various soil zones, according to geometrical rules, and an estimate of wall deflection is made. A comparison is given between the pattern of ground movement predicted by this method and that observed in centrifuge model tests. It is also shown that the use of mean mobilised strength leads to larger bending moments in the long term than the method proposed in CIRIA Report 104 (see IRRD 281371). Part one of this report was also published in Ground Engineering 1989 v22 n8 (see IRRD 827411).