The surface propagation of ground vibration

Abstract

This work involves the numerical solution of a mathematical model, which idealises the source of the ground vibration as a strip of pressure varying harmonically in time. The ground below the strip is modelled as homogeneous, isotropic and elastic, with hysteric internal damping characterised by a loss factor. For an infinite strip load, which reduces the problem to two dimensions, three ground structures have been considered: a half-space, a layer over an inflexible half-space, and a layer over a flexible half-space of different material properties to the layer. For a finite (rectangular) strip load, only the half-space ground structure has been analysed.The formulation of the problem involved partial differential equations, which are Fourier transformed and solved in the transform domain. The inverse transformation to the space domain is calculated numerically, to yield the surface displacements.For the layered ground structures, the natural modes of free propagation have been studied, and used to interpret the forced response results.The forced response problem has been extended to include masses either at the load, at the response point or between the load and response point, to study the value of isolation masses.

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