Replacement Of Rigid Soil By AnElastic Material For The Reduction OfSensitive Machine Vibrations

Elastic mountings are necessary for reducing the effect of environmental vibrations on sensitive machinery. The common method is the application of artificial polymeric, fibrous materials or metal springs as elastic mountings. Such mountings necessitate control and maintenance. It is much more attractive to use materials that do not deteriorate over time, at least for a few decades. This is due to the fact that in order to get the effect of "mass-spring" response, a heavy mass that supports the sensitive system is laid over an elastic material. At least a partial solution can be obtained by soil replacement of the rock underneath the foundation. However, it is illustrated here numerically that the result is strongly dependent on the spectrum of the system response, and in certain cases incorrect design may even cause weakening of the isolation.