| The work presented in this thesis consists of three parts: the theoretical development, experimental verification and a parametric study. In the first part, expressions for the elastodynamic displacements generated by a normal point force acting on the top layer of two isotropic layers overlaying an isotropic half-space are derived. A combinatorial technique for counting the number of wave rays simultaneously arriving at a specific point on the top surface is developed. Reflection and transmission coefficients are derived. Different ray travel paths and the corresponding products of the reflection and transmission coefficients are generated. The arrival times of various rays including head waves are obtained. A computer program has been developed for efficient numerical implementation of the formulation.;In the second part, displacement measurements are presented for experiments performed on a single plate, a two-layer plate and a two-layer-on-a-half-space configuration to verify the theoretical model. The theoretical model is first verified for point load excitation of a single plate. Measurements for different wave sources, plate materials and wave sensors are compared with each other and with theoretical results. The source functions for pencil-lead-breaks on aluminum and stainless steel plates are obtained from deconvolution of displacement signals obtained by the use of a laser interferometer. The pencil-lead source provides repeatable signals and simulates a step function. The T-PROsci conical displacement transducer provides a linear, sensitive and broad band response, is portable and can be used easily.;Next, an aluminum plate, a stainless steel plate and a thick acrylic resin plate representing a half space are bonded with a high-modulus epoxy. The interface conditions between the materials were examined with an ultrasonic C-scan inspection. The experimental results for the two-layer plate and for the two-layer-on-a-half-space configuration showed good agreement with the theoretical predictions, thus, fully verifying the performance of the theoretical model.;In the third part, the transient displacement response has been determined for various values of four input parameters of the second layer. Finally, the model has been used to simulate wave propagation in airport pavements, for both a step function input source and a simulated hammer blow source. |
