Review of peat strength, peat characterisation and constitutive modelling of peat with reference to landslides

The correct estimation of the shear strength of the peat subsoil is one of the major aspects of assessing risk of landslip in blanket peat areas. Due to the fibrous structure of the peat, its behaviour during shear is somewhat different from that of mineral soils (e.g. soft clays) and it has been found difficult to obtain reliable values of its shear strength. To estimate the shear strength of the peat, the geotechnical engineer is faced with making use of a several testing techniques, both in the laboratory and in situ, which were actually developed for mineral soils. Whether these techniques are applicable to peat is not clear. The objectives of this note are to review: 1. Available methods of characterising peat. 2. Previous research that has been carried out on estimating the shear strength of peat in Ireland and elsewhere using both laboratory and in situ testing. 3. Efforts that have been made to model peat using advanced numerical modelling. Following the review some recommendations will be made as to which test type is most applicable to peat soils and recommendations will be made for further work.