By TEBAOFLEX Jyen. Originally published on August 14, 2026.
A distributed strain-sensing trace represents strain transferred into an optical fiber. It is not automatically identical to ground displacement or structural strain. The coupling from the host material through grout and cable layers is therefore part of the measurement design, alongside the interrogator and its spatial resolution.
Trace the load-transfer path
- Host to grout: consider borehole condition, grout continuity, curing, shrinkage and compatibility with the surrounding material.
- Grout to jacket: consider surface profile, bonded length, confinement and the intended installation method.
- Jacket to sensing fiber: establish which elements are mechanically coupled and which are intentionally strain-isolated.
- Fiber to reported strain: account for calibration, temperature sensitivity, gauge length and the processing method.
A low or spreading strain peak can be consistent with slippage, but it can also reflect measurement resolution, temperature effects, changing loading or damage elsewhere. Do not diagnose debonding from one trace shape alone.
Use the actual sensing-cable drawing
Solifos publishes a BRUsens BSSH V13 hybrid design with strain-sensing fibers and separate loose-tube sensing elements, and offers smooth or structured sheath options. Those manufacturer-specific details do not support a universal rule banning smooth jackets, nor do they establish a TEBAOFLEX-made equivalent or a field bond strength.
Select the cable for the measurement objective: strain transfer is desirable for DSS, whereas temperature-reference fibers may need mechanical decoupling. A cable strain range is not proof that every grout interface transfers that range without slip.
Qualify grout and installation conditions
The geotechnical or structural designer should select the grout system, installation sequence, anchoring and any pretension. A single water-cement ratio or hanging weight cannot suit hard rock, soft soil, concrete and all cable designs. Pretension must respect the cable’s installation load and the required measurement range.
Representative trials should reproduce the jacket, grout, curing conditions, bonded length and loading mode. Compare fiber readings with an independent displacement or strain measurement, including temperature compensation and unloading behavior. Record slip, hysteresis and the useful transfer length instead of reporting only peak pullout force.
Illustrative strain calculation
For a hypothetical uniform deformation of 2 mm over 1 m, average strain is 0.002, or 2,000 microstrain. A 2 mm crack opening concentrated over a shorter transfer zone does not produce the same local strain distribution. The interrogator gauge length and cable coupling affect the measured peak. This example is not a calibration or field result.
Apply standards within their scope
General optical-cable tensile and crush tests help describe mechanical behavior but do not certify a cable-to-grout bond. ASTM D7913/D7913M concerns FRP reinforcing bars in concrete; adapting concepts from it requires an explicitly agreed cable-specific procedure, not a claim of standard conformity.
Commissioning and data-quality records
- Record cable and fiber identification, installed geometry, anchors, grout batches and curing conditions.
- Establish optical baselines and a temperature-compensation approach suitable for the interrogator.
- Retain comparison measurements and document the strain-transfer calibration or validation.
- Treat unexplained discontinuities or drift as an investigation trigger; do not infer structural safety from an unvalidated low reading.
Sources and scope
Solifos: BSSH V13 hybrid sensing cable datasheet
ASTM D7913/D7913M: scope of FRP-bar pullout testing
These references explain the relevant methods or manufacturer guidance. They do not certify a TEBAOFLEX product or establish results for a supplied batch.
Discuss your specification
For a project-specific cable specification, send the duty, installation drawing and required acceptance criteria to TEBAOFLEX. WhatsApp: +86 185 9591 3361. Request documented product ratings and test evidence before approval.