2007 Volume 49 Issue 4 Pages 309-326
The groundwater flow velocity at deep u n derground is expected as low as 10-10-10-8mis that is several orders of magnitude lower than the detection limit of conventional measurement techniques. The authors have developed a new technique to measure such a low flow velocity by using solid particle tracer coupled with ultrasonic sensors in a single borehole sectioned by a double packer system. The 3-D groundwater flow measurement system has been designed to estimate the flow in the surrounding rock medium from the data obtained in a borehole. To establish the design, the disturbance due to the presence of the devices in the measuring rod was examined by numerical analyses. The results indicated the disturbance was minimized and eliminated when the focus area (ca. 1cm3) of the ultrasonic sensors was set at the vicinity of the center of the borehole. Based on the results of numerical analyses, a proto-type vector seepage probe was fabricated and applied in the laboratory for verification. As the results, a wide range of water flow velocity 10-9-10-5m/s could be detected by the set-up of the proposed measurement system and the estimation method of groundwater flow in a measurement area was verificated.
