Vibration isolation of foundations subjected to impact loads by open trenches using physical models

Surface waves generated during vibration of machine foundations are sometimes troublemaking and cause some damages to the nearby sensitive structures or people. Considering the function of the machines located on the foundations the dynamic loading could be harmonic or impact type. The main part of the generated energy is transferred to the ground by Rayleigh surface waves. One of the most reliable and economic methods for reduction of the effects of these generated waves is using open trenches around the dynamic sources, so called active isolation in literature. In this paper applicability and affecting parameters of the open trenches around the impact dynamic source is studied using physical model tests. Cubic model container filled with loose and dry sand models. Dynamic tests were performed using drop of a tamper producing impact loads. The corresponding tests were performed for identical models with and without isolating trenches around the dynamic source. In order to record the response of the models, all models were well instrumented at different points using acceleration and soil pressure sensors. The dimension and location of the trenches are among the parameters varying for different tests. It is shown that with increasing the depth of trench efficiency of the isolation for impact is increasing. The optimum depth of the trench is affected by many parameters like the type and frequency content of the dynamic loading.