Briefing: Effective-stress strength of peat in triaxial compression

Abstract

This briefing highlights the difficulties of standard triaxial compression testing of fibrous peat and representing its behaviour in a Mohr–Coulomb framework. Experimental values of effective angle of shearing resistance φ′ and apparent cohesion c′ reported in the literature for fibrous peat are scrutinised, from which the authors conclude that high φ′ values determined from triaxial compression testing can be grossly unconservative. Furthermore, given that shearing in a peat which is not completely humified involves tearing of entangled fibres and cellular connections in addition to shearing at frictional contacts, the authors postulate that the apparent cohesion value of fibrous peat is most likely greater than zero. Hence fundamental research on peat strength and how it is derived needs to be performed; also there needs to be further development of existing and new specific material models to simulate more accurately the soft and viscous nature of peat, and the general cross-anisotropic fabric and reinforcement provided by fibres in peats with low humification.