Soil Nail and Ground Anchor Testing: QA Checklist, ITP Items, and Records
When it comes to retaining systems, the margin for error is thin. Soil nail testing and ground anchor testing are not box-ticking exercises — they are the engineered evidence that a structure will perform as designed under load, over time, and in variable ground conditions. For engineers, QA managers, and government project teams, understanding what gets tested, when hold points apply, and what records need to be maintained is essential to project sign-off and long-term liability management.
This guide covers the full QA and ITP workflow for soil nailing and ground anchoring, from proof test anchors and pull-out test procedures through to shotcrete facing inspections and non-conformance triggers.
What Gets Tested: Proof Tests and Acceptance Criteria
What is a proof test for ground anchors?
A proof test, sometimes called an acceptance test, applies a load to each installed anchor to confirm it can carry the design load without creep, relaxation, or structural failure. Under ATS 5328 (Austroads), proof tests typically load anchors to 1.25 to 1.5 times the design working load, held for a defined period while displacement is monitored.
What does a pull-out test for soil nails involve?
A pull-out test for soil nails applies incremental tensile loads to a nail to determine the bond capacity between grout and soil. Test nails are typically installed adjacent to production nails in similar ground conditions. Load is applied in stages, with displacement recorded at each increment. Failure load, creep rate, and residual movement are assessed against the design bond assumptions.
What is the difference between a proof test and a suitability test?
A suitability test (also called an investigation test) is performed prior to production anchor installation to validate design assumptions. It loads the anchor beyond the working load to establish failure modes or creep limits. A proof test is performed on production anchors to confirm each installed element meets the acceptance criteria. Suitability tests inform design; proof tests confirm construction compliance.
Which standards govern anchor and soil nail testing in Australia?
Key references include ATS 5328 for anchor testing, Transport for NSW specifications, and project-specific geotechnical design reports. State road authorities and infrastructure clients may apply additional requirements. Always confirm which edition applies to your contract.
Common ITP Hold Points
An Inspection and Test Plan (ITP) for ground anchoring or soil nailing will typically include the following hold and witness points:
- H1 — Pre-drilling check: Confirm rig setup, inclination, drill bit diameter, and position against approved anchor or nail layout drawings.
- H2 — Grout approval: Grout mix design sign-off prior to commencement. Includes w/c ratio confirmation, admixture records, and test cube casting for compressive strength.
- H3 — Anchor or nail installation: Witness installation to confirm drill depth, casing withdrawal (if applicable), grout injection volume, and tendon or bar insertion.
- H4 — Proof test or pull-out test: Hold point prior to stressing or load testing. A QA manager or a geotechnical engineer must be present. Load cells, gauges, and reference frames must be calibrated and inspected before testing begins.
- H5 — Lock-off and head construction: Confirm lock-off load, head plate seating, and corrosion protection applied before grouting or encasement.
- W1 — Shotcrete application: Witness point for shotcrete facing application. Includes pre-pour check of mesh, drainage provisions, and bearing plates.
For tunnel shotcrete lining applications, hold points are typically more frequent and may require continuous inspector attendance during spraying operations.
Records: Drill Logs, Grout, and Load Test Data
What records are required for soil nail and ground anchor installation?
The minimum record set for a compliant ITP typically includes the following:
- Drill logs: Record of drill depth, rate of penetration, flush returns, and any ground changes encountered. Anomalies such as voids, water ingress, or caving must be noted and reported to the geotechnical engineer.
- Grout records: Batch tickets, w/c ratio, injection pressure, volume injected per hole, and cube samples. Cubes are typically tested at 7 and 28 days. Any over- or under-volume injection is a non-conformance trigger.
- Load test records: Full load-extension plots for every proof test and pull-out test. Records must include applied load, jack pressure, dial gauge or LVDT readings at each load stage, creep readings over the hold period, and lock-off load confirmation.
- Calibration certificates: Jack, load cell, and gauge calibration certificates must be current and on file before testing begins.
- Photographic records: Pre-drill, during installation, tendon/bar condition prior to insertion, grout head, and head construction.
All records should be referenced against the as-built drawing number, chainages, or grid references. For government clients, records are typically submitted as part of a Quality Records Package (QRP) at practical completion.
Shotcrete Facing Checks
Shotcrete facings for soil nail walls and slope stabilisation systems require their own QA hold points separate from the nail installation ITP.
What shotcrete checks are required before spraying?
Pre-pour inspections confirm nail head bearing plates are correctly positioned and tight, drainage provisions (weepholes or geocomposite) are in place, mesh laps and cover meet specification, and the substrate is clean, damp, and free of loose material.
What is tested during and after shotcrete application?
Panels or test boards are typically shot alongside the facing to provide cores for compressive strength testing. Thickness is checked against minimum cover requirements using break-off pins or depth probes. Rebound must be removed from between mesh layers during application.
What are the acceptance criteria for shotcrete facings?
Acceptance criteria typically include a minimum 28-day compressive strength (commonly 25 MPa to 32 MPa depending on specification), minimum thickness at any point, and crack width limits. Any delamination, cracking, or failure to achieve design strength triggers a non-conformance.
Non-Conformance Triggers
The following conditions require a non-conformance report (NCR) to be raised and the geotechnical engineer notified before works proceed:
- Proof test or pull-out test result below the acceptance load or exceeding the creep limit
- Drill log indicating ground conditions that differ materially from design assumptions (voids, water, unexpected soil type)
- Grout volume injected significantly below or above the theoretical volume without explanation
- Grout cube test failure at 28 days
- Anchor or nail installed outside positional, inclination, or depth tolerances
- Shotcrete core or board strength below specified minimum
- Corrosion protection found to be damaged prior to head construction
- Lock-off load outside the specified range
NCRs must include a description of the non-conformance, the affected elements, a proposed disposition, and a geotechnical engineer’s sign-off before work continues. For government infrastructure projects, refer to SafeWork Australia excavation guidance when NCRs relate to ground disturbance or stability risk.
Frequently Asked Questions
Testing frequency varies by specification and risk category. A common requirement is one pull-out test per 50 to 100 production nails, with a minimum of two tests per wall panel or work stage. Some specifications require additional tests when ground conditions change materially. Always confirm the testing frequency with the geotechnical engineer and the QA plan before mobilisation.
Proof testing of production anchors is generally not waivable on engineered retaining systems. On very small or low-risk projects, the number of tests may be reduced with geotechnical engineer approval and contract principal agreement, but some form of load verification is typically required to demonstrate compliance with the design bond assumptions.
A failed proof test triggers an NCR. The geotechnical engineer reviews the failure mode, whether cohesive creep, bond failure, or tendon yield and determines whether additional nails or anchors are required, the design load needs to be reduced for that element, or the element must be abandoned and replaced. The disposition must be documented before work continues.
Creep is the ongoing displacement of an anchor under sustained load. A creep limit defines the maximum acceptable displacement over the hold period during a proof test, typically measured in millimetres over a log cycle of time. Exceeding the creep limit suggests the anchor is moving within the ground rather than remaining stable — a condition that may indicate progressive bond failure.
Yes. Each lift of excavation exposes a new face that must be inspected for ground conditions, seepage, or structural anomalies before drilling commences. For deeper excavations, there may be monitoring requirements under the geotechnical instrument plan. SafeWork Australia excavation requirements also apply to any excavation over 1.5 m depth.
Yes. Load test records, grout records, and as-built drawings are typically held by the principal and form part of the structure’s long-term maintenance file. For government infrastructure, record retention periods may be mandated under contract. These records become critical reference material if future works (utilities, adjacent construction) are planned near the retaining system.
Proof tests and pull-out tests should be supervised by a qualified geotechnical engineer or a suitably experienced geotechnical technician under engineer’s oversight. The test engineer must understand load-displacement behaviour, creep interpretation, and when to halt loading. Calibration of test equipment must be verified by a NATA-accredited facility.
Get QA Support
Whether you are preparing an ITP for tender, managing QA on a live retaining wall project, or reviewing records for project sign-off, Terracon Civil can provide technical support across the full testing and documentation workflow.
Our team delivers soil nailing, ground anchoring, shotcrete, and slope stabilisation services with compliant QA systems, experienced site personnel, and complete ITP record packages. Contact us to download a QA checklist or request QA support on a live job.
