Proof of Bearing Capacity of Anchors on the Example of Innovative Anchor Monitoring System-Paper

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The paper presents a distributed fibre-optic system for monitoring the load-bearing behaviour of grouted ground anchors. Unlike conventional force meters or point sensors, the system uses Rayleigh scattering to measure strain continuously along an optical cable embedded in the anchor grout body. Five 35-m anchors were instrumented and tested in accordance with DIN EN 1537, with strain measured at 1-cm intervals.<br /><br />Tests revealed a characteristic strain profile as load increased. The profile reflects changes in load transfer and bonding between the steel tendon and grout. For a given load level, the initial loading produced a distinctive strain pattern that remained substantially consistent during subsequent unloading and reloading, provided the anchor was not subjected to a greater load. This suggests the pattern can serve as a record of the anchor’s maximum experienced load and could support automated alerts if that load is exceeded. The strain pattern was also largely stable during individual load holds.<br /><br />Analysis indicated that reducing the data to measurements spaced 10 cm apart preserved the characteristic profile sufficiently, offering a way to manage the large volume of monitoring data.<br /><br />The method offers high spatial resolution, can monitor regions that are difficult to access, and uses durable fibre-optic cables. However, it requires further validation against established measurement methods and calculations. Equipment costs remain high, and readout devices need protection from moisture, vibration, and temperature effects. Further research is planned on long-term performance and whether changes in strain profiles can indicate deterioration of grout, including in chemically aggressive groundwater.

Keywords

distributed fibre-optic sensing

ground anchors

Rayleigh scattering

strain monitoring

grouted anchor

load-bearing behaviour

load transfer

bonding

high spatial resolution

DIN EN 1537