Vibration isolation in soil by thin injected foam barriers

The isolation of excessive noise and vibration plays an important role for the usability of buildings close to vibration sources, such as railway lines. By installing noise protection walls along the vibration source, the noise, which is mainly travelling through air, can be reduced remarkably. Following this principle the vibrations, which are running through the ground, can be reduced by thin vertical foam barriers, injected into the soil. These barriers could be a promising alternative to conventional vibration isolation methods, e.g. spring elements or elastomer mats. The advantages of these thin foam barriers are notable savings in material and time, because of the simpler installation procedure. However, the effectivity of those barriers has still to be proven by in situ measurements. Until now, there is no tool to predict its impact on vibrations. This paper will present first results from a field test that was carried out in a gravel pit, using a hydraulic shaker unit as vibration source. By measuring and comparing the soil velocities before and after installation of the foam barrier, the effectivity of the isolation measure has been evaluated. The promising results indicate a significant reduction of the soil velocities and are used for the calibration of a numerical model.