| Summary: | 碩士 === 朝陽科技大學 === 營建工程系碩士班 === 94 === ABSTRACT
In recent years, failures of several earth retaining structures caused severe damage in property and loss of life in Taiwan. Therefore, evaluating the safety condition of existing earth retaining structures becomes an important task for the civil engineers. However, many of these retaining structures were built long time ago. The design drawing of these structures can no longer be found. It becomes necessary to access the dimensions of these retaining structures through non-destructive testing (NDT) techniques for their safety evaluation.
The objective of this thesis is to investigate the feasibility of applying the sonic echo (SE) NDT technique for the evaluation of the height of existing earth retaining structures. Numerical modeling was performed to study the 3-dimensional effects on the measured signal using commercially available ANSYS LS-DYNA finite element software. Field tests were also performed on two earth retaining walls to verify the results from numerical modeling.
Results of this study indicate that, in comparison to 1-dimensional structures such as piles, 3-dimensional effects reduce the intensity of signal reflected from the bottom of the structures, thus increase difficulty in determining the arrival time of the reflected wave. However, this difficulty can be overcome by selecting a suitable impact source and arranging the receiver properly. Therefore, it is concluded that the sonic echo method is a very promising technique for the evaluation of the height of existing earth retaining structures.
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