|
| | Abstract | | Infiltration process of water into the surficial vadose zone of a levee system was monitored at short intervals by means of a newly developed high-speed resistivity measurement tool. The tool can transmit 24 individual current signals simultaneously and measure 24 potential responses. Because of its short interval time, only 30 seconds are spent to obtain and store a total of 576 (24 x 24) dataset. Using the system, we could conduct not only near real time monitoring but also dense 3D time-lapse resistivity measurements in the field. We set a total of 4 current lines and 4 potential lines parallel on the slope of a levee, and infused water into the vadose zone from a small trench dug on the levee crest. Electrode stakes were placed at 50 cm spacing along each line, and spacing between the lines was set to 50 cm. A total of 6,912 (12 pairs x 576) data were acquired at 5 min to 30 min. Difference inversion as well as ordinary 3D tomographic analysis, applied to the dataset composed of a total of 44 stages during the infiltration across two days, successfully imaged the extent of infiltrated water in the vadose zone. |
|
|
|
| |
|