Pile Load Test in Bangladesh: Static, Dynamic (PDA), and Integrity Testing Explained
A pile can be perfectly designed on paper and still be a question mark in the ground. SPT-based capacity equations are estimates, bored-pile concrete is placed blind under bentonite or water, and Bangladesh's layered alluvial deposits (soft clays, silts and loose-to-medium sands within a few metres of each other) make every site behave a little differently. The pile load test is how engineers turn that uncertainty into evidence. This guide explains the three families of pile testing used on Bangladeshi projects: static load testing, dynamic testing with the Pile Driving Analyzer (PDA), and pile integrity testing (PIT), with the governing standards (BNBC 2020 and ASTM), the formulas behind each method, a fully worked example, safety rules, and a free calculator you can use on site.
- Why Piles Must Be Tested
- The Three Families of Pile Testing at a Glance
- Governing Standards: BNBC 2020, ASTM and IS 2911
- Static Pile Load Test (ASTM D1143)
- Interpreting the Load–Settlement Curve & Worked Example
- Dynamic Pile Load Test: PDA and CAPWAP (ASTM D4945)
- Pile Integrity Testing: PIT, CSL and Coring (ASTM D5882)
- Which Test, When? A Practical Testing Programme
- Bangladesh Site Realities
- Common Mistakes and How to Avoid Them
- Risk & Safety Instructions
- Interactive Pile Test Calculators
- Technical References
- FAQ
Why Piles Must Be Tested
BNBC 2020 (Part 6, Chapter 3) recognises four routes to the ultimate capacity of a single vertical pile: static bearing-capacity equations (the α-method in cohesive soil and the β-method in cohesionless soil), SPT/CPT correlations, load tests, and dynamic methods. The first two are predictions. Only a load test measures what the pile and the soil actually do together, which is why ASTM D1143 describes field tests as the most reliable way to relate applied axial load to axial movement.
The gap between prediction and reality is not small. A 2026 study in Scientific Reports compared BNBC 2020 capacity equations with static load tests from six Bangladeshi projects (four PWD, two LGED; precast and cast-in-situ piles). In the Khulna clay-dominated case, the SPT-based BNBC 2020 method predicted an allowable capacity about 44% below the tested value, while in the Dhaka bridge-pile case (alternating sand and silt) the same method over-predicted by about 19%. Errors in both directions cost money: under-prediction wastes concrete and pile length; over-prediction is a safety problem. Testing is the control.
The Three Families of Pile Testing at a Glance
"Pile load test" is used loosely on site, but three quite different things hide under the name. They answer different questions, and a good testing programme uses more than one.
| Test | Question answered | Method | Relative cost / time | Governing standard |
|---|---|---|---|---|
| Static load test (SLT) | How much load does the pile carry, and how much does it settle? | Hydraulic jack against kentledge or anchor piles; load applied in steps over hours to days | Highest cost; several days per pile | ASTM D1143/D1143M; IS 2911 (Part 4); BNBC 2020 Pt 6 Ch 3 |
| High-strain dynamic test (PDA / CAPWAP) | What is the mobilised capacity, driving stress, hammer energy and shaft/toe split? | Heavy drop weight or hammer strikes the pile; strain and acceleration are recorded | Moderate; many piles per day | ASTM D4945 |
| Low-strain integrity test (PIT) | Is the shaft continuous, with no necks, cracks or voids? | Hand-held hammer tap; velocity reflections analysed | Lowest; minutes per pile | ASTM D5882 |
| Crosshole sonic logging (CSL) | Where exactly is a defect in a large bored pile? | Ultrasonic pulses between pre-installed tubes | Moderate; tubes must be cast in | ASTM D6760 |
| Bi-directional static test | Shaft and base resistance of heavily loaded shafts without a huge reaction system | Embedded jack at or near the base pushes shaft up and base down | High; planned before casting | ASTM D8169/D8169M |
| Rapid load test | Axial capacity from a single pulse lasting tens of milliseconds | Gas-pressure or mass-launch device with load cell | Moderate | ASTM D7383 |
The three bold rows are the ones that matter on almost every Bangladeshi project, and the rest of this guide concentrates on them. The key mental model: static tests give capacity and settlement for a few piles; dynamic tests give capacity estimates for many piles; integrity tests give shaft soundness for (nearly) all piles.
Governing Standards: BNBC 2020, ASTM and IS 2911
Bangladeshi practice is a hybrid. The Bangladesh National Building Code 2020 (gazetted February 2021) sets the framework, ASTM provides the test procedure, and interpretation criteria in BNBC follow the Indian Standard IS 2911 (Part 4). The research literature confirms this split: static axial compression tests in Bangladesh are generally set up per ASTM D1143, with load–settlement data interpreted using BNBC 2020 criteria that adopt the IS 2911 provisions.
| Standard | Scope | Edition to cite (confirm before use) |
|---|---|---|
| BNBC 2020, Part 6, Chapter 3 | Soils and foundations: pile capacity, factors of safety, load-test requirements and interpretation | BNBC 2020 (gazetted 11 Feb 2021) |
| ASTM D1143/D1143M | Deep foundation elements under static axial compressive load | D1143/D1143M-20e1 |
| ASTM D3689/D3689M | Static axial tensile (uplift) load | D3689/D3689M-22 |
| ASTM D3966/D3966M | Static lateral load | D3966/D3966M-22 |
| ASTM D4945 | High-strain dynamic testing of deep foundations | D4945-17; a 2026 revision (D4945-26) is listed by standards distributors |
| ASTM D5882 | Low-strain impact integrity testing | D5882-16 (revision work is in progress) |
| ASTM D6760 | Crosshole ultrasonic integrity testing of concrete deep foundations | Current edition per ASTM |
| IS 2911 (Part 4) | Load tests on piles: initial and routine tests, safe-load criteria | Latest BIS edition |
Static Pile Load Test (ASTM D1143)
Purpose and test categories
A static test applies axial compression to the pile head in controlled increments and records settlement against load and time. Two categories dominate practice, borrowed from IS 2911 (Part 4) terminology:
| Category | Pile tested | Typical maximum test load | Objective |
|---|---|---|---|
| Initial (preliminary) test | Sacrificial test pile, installed before production piling | 2 to 2.5 × design load, or to failure (spec-dependent) | Verify design capacity and settlement behaviour; calibrate the design |
| Routine (proof) test | Selected working pile, installed in production | 1.5 × design load (IS 2911); some specs use 2 × | Confirm workmanship and acceptance of the production piles |
ASTM D1143 loading procedures
- Procedure A, Quick Test: load held for short, fixed intervals; complete in under a day. Fast and economical, but it measures a more undrained, short-term response.
- Procedure B, Maintained Test: the usual standard procedure. Load is applied in increments of 25% of the design load up to 200% of design load, each increment held until the movement rate falls to about 0.25 mm/h (with a time limit), and the final load is held for many hours before unloading in stages.
- Procedure E, Constant Rate of Penetration (CRP): the pile is pushed at a constant rate (about 1 mm/min) and the required load is recorded; useful when ultimate capacity is the target.
- Procedures C, D, F and G are optional variants (cyclic, extended-creep and similar) used when the specification asks for them.
Test set-up
- Reaction system: kentledge (stacked concrete blocks or sand-filled containers on a platform), anchor piles with a reaction beam, or a combination. IS 2911 requires the reaction capacity to be at least 1.25 times the maximum test load.
- Loading: calibrated hydraulic jack and pump with a pressure gauge, backed by an in-line load cell for an independent load check.
- Settlement measurement: at least two (preferably four) dial gauges or LVDTs on an independent reference beam, plus a surveyor's level as a cross-check.
- Pile head preparation: cut and level the head, remove laitance and weak concrete, and cast a capping or steel bearing plate so the load is truly axial.
- Waiting period before testing: bored piles are generally not tested until the concrete has reached its specified strength (commonly 28 days from casting). For driven piles in clay, allow extra time for pore-pressure dissipation and set-up. Research on Bangladeshi tests notes a wait of at least about one month after installation.
Reading the result: what the settlement criteria mean
Most Bangladeshi static tests do not drive the pile to plunging failure, so the "capacity" is set by a settlement criterion rather than by a visible peak. The BNBC 2020 / IS 2911 approach, as applied in recent Bangladeshi research, works as follows:
Allowable (safe) load, Qall = lesser of: (i) ⅔ × load at 12 mm settlement, (ii) ½ × load at 10% D settlement
The 12 mm term governs for small and medium diameters; the 10% D term only becomes the governing one for large-diameter bored piles (a 1,000 mm pile reaches 100 mm at 10% D, a settlement few tests ever reach). The older BNBC text adds a failure rule of its own: a test is considered failed if the net settlement (gross settlement minus elastic shortening) exceeds 25 mm at the full test load, and a minimum factor of safety of 2 applies when capacity is assessed from load-test data.
Other interpretation methods that appear in Bangladeshi reports, and give different answers from the same data, include Davisson's offset limit, Butler and Hoy's tangent intersection, the Brinch Hansen 90% criterion, Terzaghi's 10%-of-diameter rule and the British Standard approach. In the six-project study above, the interpreted allowable capacities for a single Khulna precast pile ranged from about 662 kN to 853 kN depending on the method, which is a spread of nearly 30%. Always state the criterion in the test report and in the design basis.
Net (residual) settlement = Gross settlement − δe (or measured rebound after unloading)
Davisson offset line: δ = 3.8 mm + D(mm)/120 + (Q × L)/(A × E)
Interpreting the Load–Settlement Curve & Worked Example
Problem. A 600 mm diameter, 25 m long bored cast-in-situ pile has a design (working) load of 1,200 kN. An initial test was carried to 2.5 × design load = 3,000 kN. The recorded gross settlements at the end of each load step (illustrative data) are:
| Load (kN) | 0 | 300 | 600 | 900 | 1,200 | 1,500 | 1,800 | 2,100 | 2,400 | 2,700 | 3,000 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Settlement (mm) | 0 | 0.6 | 1.3 | 2.1 | 3.0 | 4.2 | 5.6 | 7.4 | 9.6 | 12.7 | 16.9 |
Step-by-step solution
| 1. Load at 12 mm | Between 2,400 kN (9.6 mm) and 2,700 kN (12.7 mm): P₁₂ = 2,400 + 300 × (12.0 − 9.6)/(12.7 − 9.6) = 2,632 kN |
| 2. 10% D criterion | 10% × 600 mm = 60 mm. The test only reached 16.9 mm, so this criterion cannot govern and gives no value. |
| 3. Ultimate load | Qult = P₁₂ = 2,632 kN (lesser of the available criteria) |
| 4. Allowable load | Qall = ⅔ × 2,632 = 1,755 kN |
| 5. Check against design | Qall / design load = 1,755 / 1,200 = 1.46 ≥ 1.0 → design load verified with reserve. Implied factor of safety on Qult = 2,632 / 1,200 = 2.19, above the minimum of 2 for load-test-based capacity. |
| 6. Settlement checks | At design load: 3.0 mm. At 1.5 × design (1,800 kN): 5.6 mm, which is below a 12 mm acceptance limit. At 2 × design: 9.6 mm. |
| 7. Elastic shortening (upper bound) | A = π(0.6)²/4 = 0.283 m²; at 3,000 kN, δe = 3,000 × 25 / (0.283 × 30×10⁶) ≈ 8.8 mm if the full load reached the toe. In a friction pile the true value is smaller, so net settlement at 3,000 kN is at least about 8 mm. |
Engineering reading. The curve is smooth with no abrupt break, so the pile is not near plunging failure at 2.5 × design load, and the 12 mm criterion, not geotechnical failure, sets the capacity. That is a conservative outcome. Where a project has spare test load and time, an extended load or a pile instrumented with strain gauges can show how much of the capacity is shaft versus base, and may justify shorter piles in the production phase.
Dynamic Pile Load Test: PDA and CAPWAP (ASTM D4945)
How it works
A dynamic test strikes the pile head with a heavy drop weight or pile-driving hammer. Two strain transducers and two accelerometers, bolted to opposite sides of the shaft about 1.5 to 2 pile diameters below the head, record force F(t) and velocity v(t). The Pile Driving Analyzer (PDA) converts these to a downward-travelling and an upward-travelling wave. The upward wave carries information on how much resistance the soil mobilised, as the stress pulse travels down the pile and reflects back.
Pile impedance: Z = E·A / c = ρ·c·A
Downward wave: Wd = ½ [ F(t) + Z·v(t) ] Upward wave: Wu = ½ [ F(t) − Z·v(t) ]
Wave round-trip time: 2L / c
Case method capacity
The PDA estimates capacity in real time with the closed-form Case method. With t₁ the time of the first velocity peak and t₂ = t₁ + 2L/c:
Static resistance (Case): RSP = RTL − Jc · [ F(t₁) + Z·v(t₁) − RTL ]
(equivalently RSP = (1 − Jc)·½[F₁ + Z·v₁] + (1 + Jc)·½[F₂ − Z·v₂])
Factor of safety on capacity: FS = RSP / Design load
The bracketed term in the second line is the force associated with toe velocity, so Jc scales the damping correction. The Case damping factor Jc is the biggest source of uncertainty and depends on the soil at the toe. Typical ranges used in practice are roughly 0.05 to 0.20 for clean sand, 0.15 to 0.30 for silty sand, 0.20 to 0.45 for silt, 0.40 to 0.70 for silty clay and 0.60 to 1.10 for clay; calibrate against a static test on the same site wherever possible.
Worked example: PDA Case method
A 600 mm bored pile, 25 m long (ρ = 2,400 kg/m³, c = 3,700 m/s), with a design load of 1,200 kN, is tested with a 6-tonne drop weight. The impedance is Z = ρcA = 2,400 × 3,700 × 0.283 = 2.51 × 10⁶ N·s/m = 2,511 kN·s/m. The recorded values at t₁ and t₂ (illustrative) are F₁ = 2,900 kN, Z·v₁ = 2,700 kN, F₂ = 1,800 kN and Z·v₂ = 800 kN. The toe sits in silty sand, so Jc = 0.25.
| Wave round-trip | 2L/c = 2 × 25 / 3,700 = 13.5 ms |
| Downward wave | Wd = ½ (2,900 + 2,700) = 2,800 kN |
| Upward wave | Wu = ½ (1,800 − 800) = 500 kN |
| Total resistance | RTL = 2,800 + 500 = 3,300 kN |
| Toe-velocity force | F₁ + Z·v₁ − RTL = 5,600 − 3,300 = 2,300 kN |
| Static resistance | RSP = 3,300 − 0.25 × 2,300 = 2,725 kN |
| Factor of safety | 2,725 / 1,200 = 2.27 ≥ 2.0 → acceptable |
| Damping Jc | RSP (kN) | FS on 1,200 kN | Comment |
|---|---|---|---|
| 0.10 | 3,070 | 2.56 | Clean-sand end of the range |
| 0.25 | 2,725 | 2.27 | Silty sand (adopted) |
| 0.40 | 2,380 | 1.98 | Silty-clay toe: FS falls below 2.0 |
The sensitivity table shows why a Case number alone is not enough. Moving Jc across the plausible range for a layered soil changes the answer by almost 30% and flips the acceptance decision. This is where CAPWAP (signal-matching analysis) comes in: the measured force and velocity records are matched against a numerical wave-equation model of pile and soil, which returns shaft and toe resistance separately, a simulated static load–settlement curve and soil-damping values. A reputable report states the Case result, the CAPWAP result and the Jc used, and compares them.
Requirements and limits
- Mobilisation: the blow must move the pile enough (set per blow of the order of a few millimetres) to mobilise ultimate resistance. A light hammer on a long, stiff pile will underestimate capacity. ASTM D4945 notes that results are only meaningful if sufficient movement occurs during the impact.
- Hammer sizing: as a rule of thumb, the ram weight is chosen at about 1 to 2% of the required ultimate capacity for bored piles, with a guided drop and a cushion to protect the pile head. Confirm in the test method statement.
- Restrike: driven piles in clay gain strength after driving (set-up), so a restrike days later reads higher than end-of-driving; record the time since installation with every blow.
- Operator expertise: the standard states that proper conduct and evaluation require special knowledge and experience, and that a qualified engineer should supervise data acquisition and interpretation.
- Calibration: a PDA result is strongest when correlated with at least one static test on similar piles at the same site.
Dynamic testing is a more recent entrant in Bangladeshi practice than static testing; published research notes that local engineers have only started using it in the past few years. That is changing quickly because PDA allows many more piles to be verified per project, which improves statistical confidence compared with testing one or two piles statically.
Pile Integrity Testing: PIT, CSL and Coring (ASTM D5882)
Low-strain pulse echo (PIT)
In a low-strain integrity test an operator taps the clean, level pile head with a small hand-held hammer while an accelerometer records the velocity response. The tiny stress wave travels down the shaft at speed c and reflects wherever the impedance Z = ρcA changes: at a neck, a crack, a void, inclusions, a bulge or the pile toe. ASTM D5882 provides minimum requirements, and its stated purpose is determining integrity of individual vertical or inclined piles from the velocity (required) and force (optional) response.
Expected toe echo time: tL = 2L / c
Wave speed from a known length: c = 2L / tL
Velocity reflection coefficient: R = (Z₁ − Z₂) / (Z₁ + Z₂) (Z₁ above the change, Z₂ below)
Worked example. For a 25 m pile with c = 3,700 m/s, the toe echo should arrive at 2 × 25 / 3,700 = 13.5 ms. A reflection at Δt = 5.4 ms places an anomaly at x = 3,700 × 0.0054 / 2 ≈ 10.0 m below the head. If the reflection is in the same direction as the impact pulse, the impedance drops (a neck, crack or soft zone); if it is the opposite direction, the impedance rises (a bulge or a stiffer soil layer).
Fig. 3 — Schematic PIT velocity trace (illustrative). A velocity increase after the impact pulse indicates an impedance reduction; the toe echo gives a check on pile length and wave speed.
What PIT can and cannot tell you
| Trace feature | Likely meaning | Action |
|---|---|---|
| Clear toe echo at the expected time, no earlier reflections | Continuous shaft of expected length | Accept (subject to specification) |
| Early reflection in the same direction as impact | Neck, crack, void, soil inclusion, or reduced section | Check logs; proceed to CSL, coring or a static/dynamic test |
| Reflection in the opposite direction | Bulge, or transition into a stiffer soil layer | Compare with soil log and pour records |
| No toe echo | Long pile, high shaft friction, heavily damped, or a major defect above the toe | Do not assume the pile is good; use another test |
| Toe echo earlier than expected | Pile shorter than recorded, or wave speed higher than assumed | Verify installed length against drilling and concreting records |
- Limits: PIT is best on piles with a length-to-diameter ratio up to roughly 30 to 40 (soil-dependent), and it cannot reliably quantify defect severity, detect small gradual changes or locate defects below a major reflector. It is a screening tool, not a capacity test.
- Timing: the pile head must be exposed, clean and sound; many specifications require the concrete to be at least about seven days old. Follow the project specification.
- Large bored piles: install CSL access tubes (typically one per 250–300 mm of pile diameter) and carry out crosshole ultrasonic logging (ASTM D6760) to profile concrete quality along the full length. Thermal integrity profiling (ASTM D7949) is an alternative that uses the concrete heat of hydration.
- Confirmation: when a test indicates a defect, core drilling through the shaft (and, where required, a load test) is the arbiter.
Which Test, When? A Practical Testing Programme
The three test families complement each other. A defensible programme for a pile-supported building or bridge in Bangladesh, consistent with the principles above, is the following. It is an engineering recommendation, not a code requirement, so the project specification governs.
| Stage | Test | Typical extent (confirm in specification) | Purpose |
|---|---|---|---|
| Before production piling | Initial static load test on a sacrificial test pile (instrumented if possible) | At least 1–2 per distinct soil zone or pile type | Confirm design capacity and settlement; calibrate dynamic testing |
| During production | Low-strain PIT on bored/cast-in-situ piles | Every pile, or a high percentage set by the specification | Early screening of defects while remedial options remain open |
| During production | High-strain dynamic test (PDA + CAPWAP) | Selected working piles, typically a few percent of piles | Capacity verification across the site at lower cost than static tests |
| Acceptance | Routine static load test on a working pile | Typically about 0.5–2% of piles, with at least one per site area | Final proof of workmanship; contractual acceptance |
| Large-diameter bored piles | CSL tubes + crosshole logging | All or selected piles | Defect location in deep, heavily loaded shafts |
Bangladesh Site Realities
- Variable alluvial profiles: clay-dominated sections such as Khulna and Barishal, versus sand–silt sections such as Sylhet and Dhaka bridge sites, respond differently to load. In the six-project dataset above, the BNBC 2020 SPT-based correlation suited sandy and silty layered profiles best, while the Shioi–Fukui (shaft) and Meyerhof (toe) SPT equations matched clayey profiles better. That is evidence that test-calibrated design is worth the cost.
- Test-pile cost versus risk: a single sacrificial static test is expensive, but its cost is small beside a foundation redesign discovered after production piling. Many consultants use one initial static test plus dynamic tests on production piles to balance cost and coverage.
- Monsoon logistics: kentledge platforms need firm, drained working areas; flooded or saturated pads cause differential settlement of the reaction system and unsafe stacks. Plan test windows outside peak rainfall where practical.
- Congested urban plots: in Dhaka, space for kentledge or anchor-pile layouts is limited. Anchor-pile reaction frames and bi-directional tests become more attractive on tight sites.
- Qualified operators: PDA and PIT results are only as good as the operator and the analyst. Ask for qualifications, calibration certificates for transducers and load cells, and full raw data in the report.
- Authority and client expectations: PWD, LGED, RAJUK and many private clients demand test reports prepared under a named, licensed engineer. Reports should state the standard, the interpretation criterion and the design load against which the pile passes or fails.
Common Mistakes and How to Avoid Them
| Mistake | Consequence | Correction |
|---|---|---|
| Testing too early (green concrete or before soil set-up) | Under-reads capacity or damages the pile head | Respect the specified concrete age and set-up period |
| Reference beam supported near the reaction piles | Gauges move with the ground, so settlement is mis-recorded | Place stakes clear of the test pile and anchors; cross-check with a level |
| Reporting "capacity" without stating the criterion | Designers cannot compare tests or reuse results | State the criterion (12 mm, 10% D, Davisson) and the factor of safety |
| Using a generic Jc for PDA | ±30% error in capacity (see Table above) | Run CAPWAP and calibrate to a static test |
| Skipping integrity tests on a pile that "looked fine" during casting | Hidden necking or voids discovered after the cap is cast | Test early, before cutting off and capping |
| Hydraulic jack and gauge not calibrated | Applied load unknown, with errors of 5–10% or more | Use a load cell and valid calibration certificates (typically within 6–12 months) |
| Mixing up design load and ultimate load in the test plan | Test stops short, or kentledge is under-designed | Write the max test load as a multiple of design load in the method statement |
Risk & Safety Instructions
- Kentledge instability: design kentledge stacks for at least 1.25 times the maximum test load, build them on a levelled, compacted and drained platform, keep the centre of mass over the jack, and monitor for tilt during loading. A toppling stack of several hundred tonnes is a fatal hazard.
- Hydraulic system failure: use certified jacks, hoses and fittings with a rated working pressure above the maximum, install a pressure-relief valve, never stand in line with a jack or hose, and keep a safety cage or screen between operators and the loaded system.
- Anchor-pile and rod failure: check anchor-pile tension capacity, rod threads, nuts and welds; verify that rods are plumb and have no pre-existing damage. Sudden rod rupture releases stored energy.
- Exclusion zone: establish and barricade a no-go zone around the test during loading and unloading, with a competent person controlling entry. No one should work under suspended blocks or reaction beams.
- Dynamic test hazards: keep the drop weight guided, set exclusion distances around the hammer path, secure cables and sensors before each blow, and stop if the hammer rebounds unpredictably or the pile head shows cracks. Inspect lifting gear before each use.
- Lifting and slinging: use certified cranes and slings, a banksman and a lifting plan for placing blocks, beams and PDA equipment.
- Electrical safety: keep data loggers, generators and power leads protected from rain and standing water in the monsoon season; use RCDs on all temporary supplies.
- Pile-head and noise exposure: use hard hats, safety glasses, gloves, safety shoes and hearing protection; trim and level pile heads to avoid sharp reinforcement protrusions and impalement hazards (cap exposed bars).
- Excavations and test pits: shore or batter pits around pile heads, barricade open excavations and keep the site drained to prevent collapse and drowning.
This section provides general engineering guidance and does not replace the project's site-specific Health, Safety & Environment (HSE) plan, the test method statement or the competent supervising engineer's instructions.
Interactive Pile Test Calculators
Three quick tools for site use. All calculations run in your browser; no data is sent anywhere. Figures are for planning and checking only, so verify against the project specification.
1. Static Load Test Interpreter (BNBC 2020 / IS 2911 criteria)
2. PDA Case Method Capacity
3. PIT Reflector Depth & Toe-Echo Check
Technical References
- Bangladesh National Building Code (BNBC) 2020, Part 6 — Structural Design, Chapter 3: Soils and Foundations. Housing and Building Research Institute (HBRI), gazetted 11 February 2021.
- ASTM D1143/D1143M-20e1, Standard Test Methods for Deep Foundation Elements Under Static Axial Compressive Load.
- ASTM D3689/D3689M-22 (static axial tensile load) and ASTM D3966/D3966M-22 (static lateral load).
- ASTM D4945, Standard Test Method for High-Strain Dynamic Testing of Deep Foundations (D4945-17; 2026 revision listed by standards distributors).
- ASTM D5882-16, Standard Test Method for Low Strain Impact Integrity Testing of Deep Foundations.
- ASTM D6760 (crosshole ultrasonic testing), ASTM D7383 (rapid load testing), ASTM D7949 (thermal integrity profiling), ASTM D8169/D8169M (bi-directional static testing).
- IS 2911 (Part 4), Design and Construction of Pile Foundations: Load Test on Piles, Bureau of Indian Standards.
- Bhuiyan, S., Haque, R., Khan, Z. H., Mahzuz, H. M. A. and Islam, S. (2026), "Identification of suitable methods for static pile load capacity and recommendation for BNBC 2020", Scientific Reports 16, 16972. DOI: 10.1038/s41598-026-43057-y.
- KUET ICCESD conference paper, "Interpretation methods of pile load test", comparing BNBC 2020, NAVFAC DM 7.2 and Meyerhof capacities with Bangladeshi test data.
- Rausche, F., Moses, F. and Goble, G. G. (1972), "Soil resistance predictions from pile dynamics", J. Soil Mech. Found. Div., ASCE 98(SM9): the basis of the Case method.
- Fellenius, B. H., Basics of Foundation Design (electronic edition): interpretation of static and dynamic pile tests.
Frequently Asked Questions
What is a pile load test?
A pile load test measures how a pile responds to applied load. A static load test pushes the pile with a jack and records settlement; a dynamic test strikes the pile and analyses stress waves; an integrity test taps the pile and checks the reflected signal for defects. Together they verify capacity, settlement and soundness.
Which code governs pile load testing in Bangladesh?
BNBC 2020, Part 6, Chapter 3 sets the requirements for pile capacity and load tests. In practice, static tests follow ASTM D1143 for set-up and procedure, while interpretation uses BNBC criteria that follow IS 2911 (Part 4). Dynamic and integrity tests follow ASTM D4945 and ASTM D5882. The project specification fixes the test load and acceptance limits.
How much load is applied in a static pile load test?
It depends on the test category and the specification. Initial tests on sacrificial piles are commonly taken to 2 to 2.5 times the design load (or to failure); routine tests on working piles are commonly taken to 1.5 times the design load, although some specifications use 2 times. Confirm with the project documents and your controlled copy of BNBC 2020.
What is the difference between a static load test and a PDA test?
A static test applies load gradually over hours or days and directly measures the load–settlement curve, so it is the reference method but is slow and costly. A PDA test strikes the pile with a heavy hammer and estimates capacity from stress waves (Case method and CAPWAP), allowing many more piles to be tested per day. PDA is most reliable when calibrated against at least one static test.
What does a pile integrity test (PIT) detect?
PIT detects changes in pile cross-section or concrete quality along the shaft, such as necks, cracks, voids and inclusions, and checks the pile length from the toe echo. It does not measure load capacity and has limits for very long or highly damped piles.
When can a pile be tested after casting?
Bored piles are generally load tested once the concrete reaches its specified strength, commonly 28 days after casting, with longer set-up for driven piles in clay. Low-strain integrity tests are usually allowed earlier, often after about seven days. Follow the project specification.
How is the allowable pile load determined from a static test?
Following the IS 2911 / BNBC approach used in Bangladeshi studies, the allowable load is the lesser of two-thirds of the load at 12 mm settlement and half the load at a settlement of 10% of the pile diameter. A minimum factor of safety of 2 on the ultimate load is also expected for load-test-based capacity.
Related reading on BNFEL:
Piling Works QA/QC: A Site Engineer's Checklist ·
Pile Foundation Design: AASHTO LRFD vs ACI 318-25 ·
Precast vs. Cast-in-Situ Pile Foundations.
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