Geotechnical TDR applications in the past have failed as they were, to put it bluntly, half-baked. While the surface TDR instrument may have been state of the art, little attention was paid to the cable. However the cable, together with the surrounding grout, comprise the detection system. If this "detection system" is not well defined, the program may well fail.
- Water leakage can ruin the detection capabilities of a coaxial cable. Is the cable well sealed? What are the applied pressures? How long must the cable survive?
- A strong pulse that will allow detection of faults to end of the cable is highly desirable. What is the attenuation of the cable? How much loss will result with the system as presently designed?
- Cable calibration can be important. Generally, crimps are attached to the cable to provide distance calibration. How many crimps are necessary? How will they affect cable performance?
- What geologic environment is the cable to be placed in? The compliance of the grout and the surrounding geologic material must be considered, as must the failure mode. If it is a distributed failure (as in some soils), can it even be detected with standard TDR cable?
Our belief is that TDR/OTDR system performance can be substantially improved by proper cable selection.