The d-Cable is based on a miniature inductive strain-gauge small enough to be recessed into a surrogate tubular king-wire. The gauges are configured with base-lengths of 20cm to 2m. The d-Cable will measure how a certain length of the cable bolt is stretching in response to load. Either a single strain-gauge or an array of strain gauges may be specified. These can be concentrated at locations where it is predicted that the cable may intersect a known geotechnical feature.
During manufacturing the entire strain-gauge array is independently manufactured and calibrated and then recessed into the king-wire and swaged in place. Since the technology involves strain gauges distributed within the cable rather than displacement sensors housed in an instrumentation head, the “signal processing head” of the d-Cable is reduced to a diameter equal to that of the cable. This has significant advantages in applications that require plating or pre-tensioning.
In many applications cables require posttensioning using a plate and grips. Since the readout head of the d-Cable in the same as that of the cable itself, the grips and tensioning jack can simply be placed over the end of the instrumented cable.