Soundness Evaluation Method of the Ground around the Pier Foundation against Scouring by Microtremor Measurements at Both Sides of the Bridge Piers

Abstract

The natural frequency of the bridge pier is used as an index to evaluate the soundness of pier foundation ground against scouring. It is difficult to obtain the natural frequency from microtremor in some cases, as the peak of the Fourier spectrum of the bridge piers from the microtremor does not appear clearly in many cases, unlikely that from the impact vibration test. Furthermore, conventional approaches based on microtremor require the natural frequency which is acquired recently from the impact vibration test. However, if the evaluation method based on microtremor could be put into practical use, it is advantageous in terms of cost, and suitable for constant monitoring. Therefore, we proposed a method that can automatically identify natural frequencies only from microtremor measurement results at both sides of the bridge piers, without requiring the latest result of the impact vibration test. Based on the results of measurements on the railway bridges, we showed that the natural frequency can be identified from microtremor measurement results by the proposed method.