At the Pellissippi site the investigation concerned finding hidden voids underneath the highway. It is built on a location where numerous cave-ins have occurred over the years. The objective at this site was to determine if it was possible to find new voids in the subsurface which could be expected to cause more cave-ins. At this site the Dip-Dip method was used with a 56 electrode STING/Swift system. The survey line ran parallel to the highway at a distance of about 10 m. The results obtained after inversion show 3 suspected voids, two air-filled and one probably filled with water or mud.
- The array of 56 steel electrodes were located along the highway at a location were voids were suspected. They were placed at 3m intervals along the survey line. A Swift Smart Electrode cable consisting of four 14 switch segments was connected together for this test. The measurements were automatically recorded by Sting using the built-in Dip-Dip program. A total of 685 readings were taken on this line.
- The recorded data were inverted and interpreted using the RES2DINV software package resulting in the section shown above. This interpretation was done in a matter of hours including data transfer to the Surfer software for final report printing.
- The resulting section clearly shows the presence of at least three voids, two airfilled and one probably water filled. These are located at 81, 102 and 108 m respectively. At 70m thereis an old filled-in sinkhole which clearly shows in the section too.