| 摘要 |
The assessing technique includes boring two holes for a seismic signal transmitter, and a receiver. The line joining the points traverses the area to be examined. Damped or undamped mechanical vibrations are then produced at the transmitter, and these are compared with the vibrations received after passage through the area. - The spectrum of the received vibrations is examined particularly. Low frequencies (less than 200 Hz) indicate a terrain which is relatively weak, while frequencies greater than 200 Hz, and especially those in the range 500-900 Hz indicate a more resistant terrain. The examination may be used before and after injection of cement or resin which is required to give strength.(0/15)
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