Deformation of landfill from measurements of shear wave velocity and damping

A method is developed for finding the non-linear deformation properties of a material from its shear wave velocity and damping. A way of calculating a parameter called the characteristic strain that defines a non-linear term in the equation for strain as a function of stress is given. It is shown that this parameter may be found from a measurement of damping at known strain. The method is tested on a highly deformable landfill. Initially two loaded skip tests were carried out to measure the deformation of the landfill. Shear wave velocities were obtained by a surface wave technique and seismic refraction to find the low-strain elastic properties. Damping and the corresponding strain were then found from an impact on the surface of the material. An analysis of the stress-strain behaviour, in terms of a quadratic function of strain, leads to an expression for the damping as a function of strain that depends upon the characteristic strain. Thus this parameter can be obtained from the damping and strain measurement. The immediate settlement in the fill, under the skips, was calculated from these measured properties using a non-linear finite element program. Close agreement with observation was obtained when a scaling factor was used to take stiffness anisotropy into account.