The morphology, succession and flora of British mires is briefly outlined and the influence of these factors on the index and mechanical properties of the associated peat is discussed.
Peat, in view of its exceptionally high water content, is an extraordinary material, yet in many respects it may be regarded as ordinary in as much as the correlations between its various properties and behavioural parameters are little different from those of clay soils except in regard to strength. The cation exchange ability of peat is extremely high and exerts an important influence on its properties. The properties and parameters of some UK bog and fen peats are compared with peats from Canada and other countries.
It is shown that under constrained deformation the so-called secondary compression is the dominant and fundamental process; the consolidation phase is properly regarded as but a temporary aberration. It follows from this that the so-called preconsolidation pressure is a function of the test procedure and thickness of the peat, sample or layer. A fundamental preconsolidation pressure, both time and load induced, does exist but its determination is difficult. Current testing procedures are examined and the errors involved in conventional methods of predicting settlements are explored and evaluated.
The shear strength of peat and the stability of works over mires are not discussed.