Development of a direct simple shear apparatus for peat

This paper discusses the design and development of a new direct simple shear (DSS)
apparatus for testing peat soils. The apparatus has been designed to test peat at low
effective stresses, representative of its in-situ condition and allow the deformation of
the specimen to be monitored. This device uses Particle Image Velocimetry (PIV)
image analysis techniques to monitor the side of the peat specimen and provide an
insight into the behaviour of peat during shearing. A set of comparative tests on
remoulded clay have been conducted with another widely used DSS apparatus and has
shown both to yield similar undrained strength ratios (su/σ'vc) for a range of stress
levels. Application of the apparatus to peat soils is demonstrated by a set of tests on a
high water content blanket bog peat. Analysis of these tests using the PIV technique
reveals the complex shear strain and volumetric strain behaviour of peat undergoing
shearing. Identification of partial slippage of a specimen is also demonstrated through
these analyses.