Soil nailing · QA/QC · BS 8081 Table 7
Soil nail pull-out test in Malaysia.
A working reference for consulting engineers, site engineers, and QS on soil nail pull-out testing in Malaysian projects. Five test types per BS 8081 Table 7 and BS 8006-2: investigation, suitability, acceptance, proof, and creep. Acceptance criteria, equipment setup, sample test report layout, common failure modes, and load-displacement curve interpretation. CIDB G7 in-house testing with calibrated load cells and ISO 9001:2015 traceable records. Federal corridor project experience: EKVE 450,000 m squared protected, ECRL Section 3 along 42 km and 64 km of alignment.
5 tests
BS 8081 Table 7 in-house
200-1000 kN
Hydraulic jack capacity range
Less than 1 mm
Creep limit between 1-10 min log-decade
G7
CIDB highest grade
Engineering note
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01 / Five test types per BS 8081 Table 7
What each test actually verifies.
| Test type | Purpose | When | Typical frequency |
|---|---|---|---|
| Investigation | Loaded to failure on sacrificial nails to verify grout-soil bond and inform production nail spacing and length | Pre-production | 3-5 nails per site |
| Suitability | Confirm production technique works on the actual site soil before mass mobilisation | Pre-production / early production | 1 in 30 nails or per 1000 m squared |
| Acceptance | Proof load on production nails at 1.25-1.5 x DWL to confirm each nail meets design capacity | Production | 1 in 10 typical (1 in 5 or 1 in 6 federal corridor) |
| Proof | Project-specific representative nail testing | Production | Per consultant spec |
| Creep | Sustained-load displacement measurement per log-decade time to verify long-term performance | Production (selected nails) | Most loaded layer + deepest + one per stratum |
02 / Acceptance criteria
What defines a PASS or FAIL.
| Criterion | Threshold | Reference |
|---|---|---|
| Test load achieved without bar yield | 1.25 to 1.5 x DWL (Design Working Load) typical | BS 8081 / BS 8006-2 / project spec |
| Total elastic + plastic displacement at test load | Less than 15 mm typical for residual soil sites at DWL | Project spec, varies by ground |
| Creep displacement between 1 min and 10 min log-decade at 100 percent DWL | Less than 1 mm | BS 8081 Table 7 (mandatory) |
| Back-calculated bond stress meets or exceeds design assumption | tau_calc = F / (pi x d x L_b) greater than tau_design | BS 8006-2 Section 6 |
| Pre-loaded zero-reading repeatability | Within 5 percent on reload | BS 8081 |
Where DWL is the Design Working Load per the nail design calculation per BS 8006-2 (typical 100-300 kN for residential / commercial soil nail walls, 200-400 kN for federal corridor scope). tau_calc = test load divided by (pi x bar diameter x bond length).
03 / Test equipment register
What's deployed on a typical test.
| Equipment | Specification |
|---|---|
| Hydraulic hollow-ram jack | Capacity 200-1000 kN depending on DWL. Calibration certificate dated within 6 months. Traceable to SIRIM or national standard. |
| Electronic load cell | Calibrated digital load cell as primary measurement. Hydraulic pressure gauge as backup. Cross-check at each load step. |
| Displacement transducers | LVDT (Linear Variable Differential Transformer) or dial gauges. Two for redundancy. Mounted on independent reference beam. |
| Reference beam | Anchored to ground beyond influence zone (typical 3-5 m offset from test nail). Provides stable datum for displacement measurement. |
| Reaction frame | Bears on slope face through bearing plate. Steel I-beam or H-beam typical. Stiffness greater than 10 x bar stiffness to avoid frame deformation contaminating displacement reading. |
| Bearing plate | Plate area sized to distribute reaction load without facing damage. Typical 300 x 300 mm or 400 x 400 mm. |
| Hydraulic pump | Manual control or programmable load schedule. Pressure stability less than 1 percent during sustained holds. |
| Data logger | Time-stamped pressure and displacement recording. ISO 9001:2015 traceable records. Daily backup. |
04 / Sample test report layout
What the test report contains.
- Project identification: contract reference, project name, contract authority, test date, weather conditions, witness register.
- Nail identification: nail number, station / chainage / grid reference, slope face location, design working load (DWL), design grout-soil bond stress (tau_design), bar grade (Y20 / Y25 / Y32 or hollow bar R32-R76), bond length L_b, free length L_f, inclination angle below horizontal, drilling method (rotary auger / rotary percussion / self-drilling), grouting method (gravity / pressure), grout mix (water-cement ratio, additives), grouting date and time, time elapsed since grouting at test date.
- Equipment register: list of jack, load cell, LVDT, reference beam, calibration certificate numbers and dates.
- Test procedure: load schedule (cycle steps, hold times, increment magnitudes), pre-loading and zeroing procedure.
- Tabulated readings: load step, time of load application, load reading (kN), displacement reading 1 (mm), displacement reading 2 (mm), mean displacement (mm), notes.
- Load-displacement curve: graph with load on Y-axis, displacement on X-axis. Marked: linear elastic range, design working load, maximum test load, residual displacement after unload.
- Creep curve (for creep tests): displacement on Y-axis, log time on X-axis. Computed creep coefficient (alpha = delta_displacement per log-decade).
- Back-calculated bond stress: tau_calc = test load / (pi x bar diameter x bond length). Compared against tau_design.
- Acceptance determination: each criterion checked, PASS / FAIL marked, comments.
- Sign-off: testing engineer signature, date, submission for consulting engineer acceptance, witness signatures.
05 / Common failure modes
What goes wrong, and what it means.
| Observed failure | Likely cause | Action |
|---|---|---|
| Premature pullout at low load | Inadequate grouting (grout did not fill annulus); grout too young; bad bond zone | Hold programme. Investigate grouting procedure. Re-grout or replace nail. Review pressure-grouting application. |
| Excessive displacement at design load | Lower-than-assumed grout-soil bond stress; weaker ground than assumed | Design review. Possibly tighter spacing or longer bond length. Additional investigation tests in same zone. |
| Bar yielding before bond pullout | Either over-design (extra capacity, harmless) or under-design (rare; needs check) | Verify bar grade. Cross-check design tensile capacity. May indicate over-conservative design. |
| Creep failure (greater than 1 mm per log-decade) | Soft or weathered residual soil; insufficient grout cure time; very fine soil with viscous behaviour | Extend cure time before next test. Reduce DWL for creep-prone ground. Adjust spacing. |
| Reaction frame movement | Equipment issue, not nail performance | Stiffer frame. Recheck reference beam anchorage. |
| Inconsistent results across nominally identical nails | Ground heterogeneity (boulder, lens of weak material, varying weathering grade) | Additional boreholes. Site-specific spacing adjustment. |
06 / Load-displacement curve interpretation
How to read the graph.
- Linear elastic phase: initial steeply-sloped portion of the curve. Load-displacement relationship is roughly linear. Slope correlates with the composite stiffness of nail (bar) + grout + ground bond. Steeper slope = stiffer system.
- Yield onset: deviation from linear behaviour. May indicate initial plastic strain in the bond zone, micro-debonding, or bar yield (rare at DWL but possible at higher test loads).
- Plastic phase: shallower slope after yield onset. Bond zone progressively debonds or ground yields.
- Failure / asymptote: displacement increases rapidly at near-constant load. Either bond pullout (more displacement at same load) or bar yield (load drop with increasing displacement).
- Unload curve: residual displacement after unload. Indicates the proportion of plastic vs elastic deformation. Per BS 8081: residual displacement after unload at any test load should not exceed 50 percent of total displacement at that load.
- Reload (where conducted): reload zero should match original zero within 5 percent (per BS 8081). Significant mismatch indicates instrumentation drift or frame yielding.
07 / Standards register
What governs each test.
| Standard | Section / coverage |
|---|---|
| BS 8081:2015+A2:2018 | Table 7 specifies five test types and creep limit (less than 1 mm between 1-10 min log-decade) |
| BS 8006-2:2011 | Section 6 covers soil nail testing methodology |
| FHWA-NHI-14-007 | US methodology cross-referenced in Malaysian practice |
| BS EN 14490:2010 | Execution of special geotechnical works, soil nailing |
| JKR Slope Engineering Manual | Malaysian federal-works alignment |
| JKR-SPJ Section 7 | Earthworks and slope, federal road and government building works |
| SIRIM / national calibration standards | Equipment calibration certificate traceability |
| ISO 9001:2015 | Quality management and traceable records for test documentation |
08 / FAQ
Engineers and QS usually ask:
Can you provide independent third-party witnessing? +
Yes. Routine for federal corridor scope. Independent third-party witness (consultant geotechnical engineer or appointed third-party testing house) attends the test, signs the record, and verifies acceptance against criteria. Cost for independent witness arranged separately or included per consultant spec.
What if a test fails the acceptance criteria? +
Standard escalation. (1) Re-test on adjacent nail to rule out localised cause. (2) If failure pattern confirmed: hold subsequent production batch, investigate root cause, design review with consultant. (3) Remedial action: tighter spacing, longer length, alternative grouting method, or replacement of failed nail with adjacent compensating nail per consultant approval. (4) Documentation: failure report submitted to consultant with proposed remedial action and revised QA programme.
How long does a creep test take? +
Standard creep test sequence per BS 8081: load to DWL, hold for log-time sequence 1 min, 5 min, 10 min, 30 min, 60 min, 6 hr, 24 hr (or per project spec). Total test duration typically 1 to 25 hours depending on spec. Multi-load creep tests at multiple DWL fractions extend further. Scheduling considers nail accessibility, weather windows, and witness availability.
How quickly can you mobilise a pull-out test crew? +
Klang Valley: 24-48 hours from instruction. Other West Malaysia states: 48-72 hours. East Malaysia: 5-7 days project-specific. Calibration certificates of all equipment confirmed in advance with consulting engineer. ISO 9001:2015 traceable records on every test.
Do you do test-rig calibration on site? +
Calibration is done off-site at certified calibration houses (SIRIM-traceable). Calibration certificate dated within 6 months is mandatory. On-site we check baseline-zero stability before each test, cross-check pressure gauge against electronic load cell, and verify reference beam stability. Pre-test setup checks documented in the test report.
09 / Related references
Where this connects.
Soil nailing hub →
Full soil nailing technical reference.
Soil nail contractor →
CIDB G7 installation contractor with federal corridor experience.
Soil nailing cost →
Pricing with testing programme included.
Soil nailing design and build →
Turnkey EPC including full testing programme.
Standards reference →
BS 8081, BS 8006-2, FHWA-NHI-14-007, BS EN 14490.
Glossary →
DWL, bond stress, creep, load-displacement defined.
Credentials →
CIDB G7, ISO 9001:2015, federal corridor track record.
23 client projects →
EKVE, ECRL, township slope works.
Need soil nail pull-out testing?
Send spec + programme + project location. Same-day quote with crew availability, calibration certificate copies, and price. CIDB G7 + ISO 9001:2015 + EKVE / ECRL track record.