MODELING FREE-FIELD CONDITIONS IN CENTRIFUGE MODELS

Stress waves generated by local excitation from machines travel away from a source and eventually are absorbed in the earth. Centrifuge models are plagued by the fact that such waves reflect off the sides of the sample container and distort the desired experimental conditions. The use of Duxseal in treating the boundaries of the container is tested and evaluated as to its efficacy in alleviating the reflection problem for a class of foundation vibration problems. The results are positive for small-size sand centrifuge models subject to free surface vertical excitation, especially if the wall coverings are grooved. The prototype size corresponds to a depth and radius of 25—50 ft. A formula for the influence of a rigid substratum on natural frequency of vertical oscillation of a circular foundation is found. © ASCE.