2012 SAGEEP 研討會 專頁 (摘要)
Application of Elastic Wave Tomography for Dam Safety
Sheng-Hsung Hsieh1, Chih-Hsien Hsieh1, Chih-Hsin Hu1,
Jen-Kai Huang2, Cheng-Yang Yen2, Wen-Lung Chi2,
Non-destructive testing (NDT) is the major method for inspecting material
defects. However, the NTD using ultrasonic, radiographic, or Impact Echo
method cannot accurately detect the inner defects of huge structures, such as
a dam. On the other hand, elastic wave tomography, a non-intrusive
geophysical technique, can generate a cross sectional picture of an object. With
properly-set parameters and geometries of the elastic wave tomography, the
inner defects or material properties of a dam can be detected reliably.
Seismic tomography is based on ray tracing and wave diffraction (or
scattering). The region bordered by sources and receivers is divided into
rectangular cells (or pixels). With the information of wave field (travel times or
amplitude), the velocity fields of cells can be solved. The velocity profiles
obtained are then utilized to evaluate the properties of a structure at the area
between sources and receivers.
This paper gives some case studies. ShinGang dam was partially damaged
by the Chi-Chi Taiwan earthquake in 1999 and has been repaired. After 10
years, seismic tomography method was employed to check the safety of the
dam. The results of velocity profiles obtained are consistent with the testing at
laboratory and field. Chonggui dam was built over 70 years ago in Nantou, the
central area of Taiwan. The results of velocity profiles show the dam structure
is still in good condition. For some embankment dams, use seismic
tomography, the velocity profiles of the filled materials are revealed. The
Seismic velocities show consistent results with those obtained by other
geophysical methods, like electric resistivity tomography (ERT) .
Key Words: Elastic Wave Tomography, Non-Destructive Testing (NDT).
1. H.C.K. Geophysical Company.
2. Liming Engineering Consultants Co., Ltd.
3 . Hsiuping University of Science and Technology