INVESTIGATION INTO SHEAR STRENGTH OF PEAT

ABSTRACT: Results of CU triaxial compression tests on remolded peat specimens retrieved from a site located in Rivière-du-Loup in Quebec, Canada are presented. The remolded specimens showed different anisotropic behavior with increasing axial strain, indicating the fibers tend to align their faces perpendicular to the direction of loading. Microstructural reconstruction of the fibers is diminishing at the end of elasticity. The anisotropic behaviour induced by specimen preparation is totally different from that by shear deformation. The pore pressure parameter ‘a’, and the failure mode of the remolded peat specimens exhibit great dependency on the initial mean effective confining stress, ranging between twist and bulging failure. A more reasonable procedure to estimate the shear strength of fibrous peat, incorporating the fiber reinforcement is described. It involves following the almost linear portion of effective stress path, which corresponds to the linear strain-hardening portion of the stress-strain curve. This will obtain the deviator stress by intersecting the tension cut-off line. The shear strength parameters, with an apparent angle of shearing resistance of 34º and considerable amount of effective cohesion of 4.5 kPa, thus, can be obtained. Further studies are recommended to find a better understanding of the efficiency of this method in safety evaluation of infrastructures built on fibrous peat.