A quality control test that measures on site whether an anchor or rock bolt drilled and grouted in place carries its design load: axial tension, stepwise loading, displacement record, test report. Done at the request of the specification, the supervising engineer or the client; also on other manufacturers’ anchors.
What it measures
A pull-out test applies an axial tensile load to an anchor or rock bolt installed on site and records its load–displacement behaviour. It answers a single question: does this anchor carry, in this ground, the force assigned to it in the calculation? The drill hole diameter, the grout fill and the bond between bar and ground are assumed in the calculation; the test turns that assumption into a measurement.
Why it is done
| Reason | What is learned |
|---|---|
| Workmanship | That drilling, grouting and bar placement were done to specification |
| Capacity | That the anchor carries enough capacity for the failure mode it was designed for (pull-out, rock or concrete cone breakout, steel failure) |
| Design verification | Through the investigation test and the suitability test: whether the ground–grout bond matches the value used in the calculation; correction of the anchor length if needed (the acceptance test on a production anchor does not measure the bond) |
There are three kinds of test and their purposes differ: the investigation test (research; on a separate test anchor it establishes the bond and the required length), the suitability test (shows that the design is adequate in that ground) and the acceptance test (shows that a production anchor meets the acceptance criterion at the test load). The number and load of each kind are written separately in the specification. None of them is enough alone: the documents of the anchor bar and of the system (European Technical Assessment, material certificates, corrosion protection) go into the file together with the test.
Who asks for it
- The specification: execution of a prestressed ground anchor depends on EN 1537 and its testing on EN ISO 22477-5; execution of soil nails and rock bolts depends on EN 14490 and their testing on ISO 22477-6. The number of tests and the load are written in figures in the specification; every prestressed anchor goes through an acceptance test. The acceptance criterion is taken from the national annex of EN 1997-1 (EN 1997-3 in the second generation).
- The supervising engineer or the client: independent verification before acceptance.
- The contractor: to document its own workmanship; on every anchored line we install we recommend sample testing even when the specification does not require it.
How it is done
A hydraulic jack and a load cell are seated on the anchor head and the displacement is read with a dial gauge; the load is applied in the steps given in the specification, each step is held for the set time, and permanent and elastic displacement are separated. The result is delivered as a load–displacement graph and a test report; the acceptance criterion (test load; for a prestressed anchor the creep or load-loss limit at the test load and the visible free length, for nails and bolts the creep or displacement limit defined in the project) comes from the specification and is not made up on site. The number of tests and the load are included in the anchored slope stabilization specification (Turkish) and the barrier specification (Turkish) texts.
The test report is attached to the "installation" record on the line's barrier tag; in later inspections the anchor head is compared with this record. It is a system-independent service: it is also done on other manufacturers' anchors and bolts. For a quotation, contact.