6. Summary and conclusions
Within this paper, a case study that focuses on the foundation design and vibration isolation of a high precision instrument exposed to ground borne vibrations was discussed in detail. The sensitive instrument will be located at ground level where it may be subjected to the external vibration sources including heavy moving vehicles. For the proper operation of the sensitive equipment, in this specific case, RMS peak acceleration magnitude of vibrations under the base pedestal of the instrument should not exceed 50 μg in the frequency range of 1–300 Hz. As the initial step of the design process of the case-specific vibration isolation system, static and dynamic characteristics of the soil layers at the site were investigated by utilizing geotechnical and geophysical surveys. Consequently, to predict the ground-borne vibration levels and frequency content, an extensive site vibration measurement program was performed. Measurements at the probable location of the sensitive instrument were taken for two different scenarios where heavy trucks with rubber tires and crawler vehicles are the main sources of ground borne vibrations. Vibration levels at the points were monitored simultaneously in three mutually perpendicular axes in order to investigate the attenuation of ground borne vibrations within the soils at the site. Finally, vibration levels were measured after the construction of isolation system to determine the actual performance of the designed vibration isolation system. The measurements taken after the construction of foundation showed that designed vibration isolation system was able to reduce the vibrations to acceptable levels. Thus, findings of this research study might provide a preliminary guideline in the initial design of similar vibration isolation systems. Based on the results of this case specific vibration isolation system design, following conclusions were drawn: