圓錐貫入試驗中土壤音壓之研究

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题名:	圓錐貫入試驗中土壤音壓之研究
作者:	何家榮;Jia-Rong He
贡献者:	土木工程研究所
关键词:	方均根音壓;圓錐貫入阻抗;微震音放射;RMS sound pressure;cone resistance
日期:	2001-07-17
上传时间:	2009-09-18 17:08:47 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	傳統的圓錐貫入試驗可量測錐尖阻抗、袖管摩擦力及孔隙水壓等數據。然而，在土壤層面處，錐尖阻抗無法正確地量測，因此無法準確偵測出土壤層面的位置。本研究在錐尖內部加裝一微音器，擷取圓錐在貫入過程中產生之音波，利用微震音放射之高敏感度，探討砂土之音波特性與錐尖阻抗之關係。本研究使用一大型剛性土槽進行一系列之室內試驗，採用移動式霣降儀製作試體，對試體施加一預定之氣壓，並以等速率貫入方式進行微音錐貫入試驗。針對砂土於不同相對密度與垂直應力之條件，探討音波反應、錐尖阻抗在貫入過程之變化。針對不同相對密度與垂直應力之各組試驗，相對密度或垂直應力愈大，所得之錐尖阻抗愈大。而由微震音放射計算所得之方均根音壓亦隨相對密度或垂直應力之增加而變大。頻譜分析中，各組試驗之主要頻率約為2.3kHz，音壓約在0.1∼0.2Pa之間，此二特性對本研究之砂土具有代表性。音射分析中，音射速率隨相對密度、垂直應力增加而增大。 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.
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