|dc.description.abstract||Cone penetration tests can measure tip resistance, sleeve friction, and pore water pressure. However, the magnitude of tip resistance cannot be measured correctly at the interface of soil layer, and the position of this interface can not be detected accurately. This research installed a mini microphone in the cone tip to measure the sound wave in the process of penetration. By using this high sensitive acoustic emission, the relationships between acoustic characteristics and tip resistance of sand were investigated.
This research used a large steel tank and an acoustic cone to carry out a series of laboratory cone penetration tests. The specimens were made by a movable sand pluviator. Constant pressures were applied on the sand specimens, and then penetrated the cone into the specimens with a constant speed. Under the conditions of different relative densities of sand and different vertical pressures, the variations of acoustic emission and tip resistance during the penetration were investigated.
From the experimental results, it is understood that the tip resistance increased with the relative densities and vertical pressures. The root mean square values of sound pressure which were obtained from the calculation of acoustic emission, and the values of sound pressure also increased with the relative densities and vertical pressures.
In frequency analysis, the major frequency of each test is about 2.3kHz, and it’s sound pressure is about 0.1~0.2Pa, these properties can represent the speciality of the sand which is used in this research. In acoustic emission analyses, the rate of AE count increased with the relative densities and vertical pressures.||en_US|