Assessment of the Dynamic Properties of Holocene Peat

The dynamic behavior of a peat deposit in the north of the Netherlands is described. The organic content ranges from 70% to 95%, which is high compared to the organic content generally presented in publications on the dynamic behavior of peats. Shear wave velocities vs and correspondingly small-strain shear moduli G0 closely match values stated in the literature. Correlations stated in the literature for predicting G0 proved to be applicable. Resonant column and cyclic direct simple shear tests were performed to establish the shear modulus reduction curves and damping curves. Excess pore pressure development during testing indicates dilatant behavior. The general trend shows nearly flat shear modulus reduction and damping curves at small strains regardless of organic content. Cyclic direct simple shear tests on humified material showed a larger pore pressure buildup than found in tests on non-to-moderately humified material. Differences in degree of humification did not result in significant differences in the shear modulus reduction curve, including G0 values. Large scatter was found in the damping curves. For the humified material, tested at low stress level, a discontinuity in the damping curve is found at shear strain of 3%, which corresponds to a rapid pore pressure buildup in the tests.