DESIGN TOOLS FOR ISOLATION OF STRUCTURES BY SOIL REPLACEMENT AGAINST UNDERGROUND VIBRATIONS

Dynamic interactions if structures due to vibrating ground. The amplitudes of vibrations in the structure depend very much on the kind of interaction between the ground and the structure. If the mismatch between the ground and the structure will be strong - such as in the case of rigid rock and concrete structure the structure may vibrate roughly. To avoid excessive vibration due to excitation excitations nearby sources such as large machines, different kinds of transportation or earthquakes an elastic separation is regularly used. However, artificial separation (metal springs, rubber or others need generally maintenance or use rare and expensive materials. Also, their production and transport can demand a large amount of energy. Hence, replacement of rigid ground layer by a soft earth, or adding a soft ground layer can be a reasonable substitute to the artificial materials to reduce violent vibrations into acceptable vibrations within the limits specified in ecological and technical standards. Hence, when possible, vibrations that are expected to exceed standard limits call for protective measures that use soft ground or crushed rock. In some cases ground replacement is the ultimate solution. To establish all this approach, the ground materials should be categorized like we do with springs, introducing to the analysis various kinds of soft grounds and giving to the foundations engineer practical tools for design. Numerical examples using elastic layers of even 0.5 m thickness result in effective vibration isolation in wide frequency bands.