Dynamic response of Mercer Slough peat

The behavior of a peat from Mercer Slough in Bellevue, Wash., was investiga ted by a program of field and laboratory testing. The peat was very soft, v ery weak, and highly compressible. Water contents averaged approximately 60 0% and in situ shear wave velocities were measured at 12-30 m/s. Cyclic tri axial and resonant column testing indicated that the modulus reduction and damping behavior of Mercer Slough peat was significantly influenced by stra in amplitude and effective confining pressure and was weakly influenced by loading frequency and overconsolidation ratio. Comparison of the behavior o f Mercer Slough pear with other highly organic soils suggests a trend of in creasing linearity and decreasing damping with increasing effective confini ng pressure. Site response analyses indicated strong response at low freque ncies with spectral shapes that differ significantly from the standard shap es implied by current codes.