| Summary: | 碩士 === 國立中央大學 === 土木工程研究所 === 94 === According to the results of past researches about acoustic cone, it is understood that the acoustic cone can be used to measure cone resistance and root mean square of sound pressure. It is also found that the acoustic cone is sensitive in measuring small sound wave due to a small variation in ground. This research used the measuring technique of sound to record the sound waves in soil during slide. In the future, this technique may be expected to establish a monitoring system for recording small variation of soil behaviors.
This research measured the Acoustic Emission (AE) of soil during the penetration of cone tip in the testing chamber and realized some basic characteristics of soil. In addition, a sound wave propagation test was conducted in the test pit to realize the sound wave transmission in sand layer. Finally, a sand slide model test was performed to simulate the movement of retaining wall and the sound signals were recorded during the slide of sand.
From the results of experiments, it is found that the cone resistance, the root mean square of sound pressure and AE rate increased with the increase of relative density and overburden pressure. Increase the relative density of sand can increase the cone resistance and the root mean square of sound pressure effectively. The amplitude of sound wave will decrease gradually during the transmission in loose sand layer and the root mean square of sound pressure will decrease in inverse proportion with the increase of distance from sound source. From the results of ACPT, the major frequency of sound signals is located at the range of 2~4.5kHz, and for sand slide model test, it located at 5Hz. These experimental results show that the sound signal with high frequency will be generated due to the bump of sand particles during the penetration of cone tip. However, the sound signal with low frequency will be generated during the sand slide under the condition of unloading.
|
|---|
