| Summary: | 碩士 === 國立中央大學 === 土木工程學系 === 102 === The nets of highway and railway are extending to everywhere in Taiwan. To protect the environment of the surrounding area or to keep the safety of transportation, many parts of these traffic constructions maybe designed as bridge which may be supported by pier and pile foundations. When vehicles or trains pass through these constructions, some impact or vibration loading will be caused. This kind of loading energy maybe transferred to the piers and the piles. This may cause vibration of the surrounding soil layer or settlement of the pile foundation. This research tried to set a shock absorber on pile head to improve the transfer mechanism of shock loading, and expect to reduce the vibration on soil and settlement of pile foundation. A series of model pile tests were performed in laboratory. In these tests, the Danang sand was filled in a cylindrical test pit to simulate sand layer and a steel pipe was set at the center of this test pit as model pile. Drop a steel hammer with various heights on the head of model pile to simulate the shock or loading of passing vehicle or train. The acceleration data was measured with accelerometers set at various imbedded depth of model pile. And the permanent settlement of pile shaft and dynamic displacement of shock absorber were measured with two sets of LVDT. The experimental results showed that an excellent improvement effect is obtained by setting a shock absorber on pile head. For instance, the permanent settlement of model pile improved with shock absorber is reduced to 0.0135mm, while the value of the untreated model pile is 0.061mm. Moreover, the maximum dynamic displacement of shock absorber is 0.0879mm which is smaller than the value limited by the design code. It is also observed that the vibrations at various depths of soil are reduced effectively.
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