Development of a borehole radar system and its field experiments for the base of crosshole tomography
- Tokyo Electric Power Co. (Japan)
- OYO Corp., Saitama (Japan)
This paper first describes the outline of the authors` borehole radar system developed for crosshole radar tomography that can be applied to imaging the grouting sphere throughout the foundation rocks at dam construction sites. Then, the results of some field experiments using the system are described. They were conducted at a test field in a soil ground and under the water at a dam reservoir to examine the quality of the electromagnetic waveforms acquired by the system and the directivity of the antennas. The waveform data from the experiments at the soil ground showed that the system had high accuracy and stability so that one could see the reciprocity even in the actual field. The directivity of the antenna was isotropic in the horizontal plane, while in the vertical plane, it showed a radiation pattern with slightly narrower half beamwidth compared with that defined for a dipole antenna in the air. In addition, it was found that the travel times of first arrivals in the water showed some errors in case when the distance between transmitter and receiver was very short and the angle of elevation between them was greater than 45{degree}. It might be a near-field effect. As the result, the borehole radar developed here is considered as a practical system that can be used in crosshole measurements for tomography in actual fields.
- OSTI ID:
- 80233
- Report Number(s):
- CONF-941015--
- Country of Publication:
- United States
- Language:
- English
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