Why Test Piles?

Testing is needed to confirm two main things: load capacity (Capacity), that the pile actually carries the design load, and integrity (Integrity), that the pile has no internal defects. Piles are underground and cannot be seen after construction. If a pile cannot carry the design load, or has cracks, segregated concrete or insufficient length, the building may settle later.

Each test method answers a different question. This article summarizes all methods in one place, with links to the dedicated article for each method. For the legal requirements, see the summary in Pile testing under the 2023 Foundation Ministerial Regulation

The SPN engineering team testing pile load capacity with a Dynamic Load Test (PDA) at a warehouse project site
Pile testing on an actual site by the SPN engineering team — testing helps confirm both the load capacity and the integrity of piles before acceptance (Photo: SPN Soil Engineering)

How Many Types of Pile Testing Are There?

Pile testing has 3 main methods, classified by what is measured and the level of force applied to the pile, plus 2 supplementary methods for checking the concrete of bored piles:

  • Seismic Integrity Test (Low Strain) — a light tap with a hand hammer on the pile head checks "integrity" and length. Low impact force, economical, fast, and suitable for testing large numbers of piles
  • Dynamic Load Test (PDA, High Strain) — a drop weight delivers a high-strain impact and stress waves are measured to evaluate "load capacity". Several piles can be tested per day
  • Static Load Test — real load is applied directly to the pile, so it serves as the reference value for load capacity, but it is slow and costly, so usually only a few piles are tested
  • Supplementary methods for bored piles — Cross Hole Sonic Logging (CSL) sends sound waves between tubes cast into the pile to check the integrity of large-diameter bored piles, and the Coring Test drills concrete cores out of the pile body to check quality

The figure below brings all methods together in one map. The three upper cards are arranged from low force to high force and show what each method measures, how fast it is and which standard it references. The bottom strip helps you choose a method based on the question you need answered.

Map of all pile testing methods in one image: the three main methods arranged by the level of force applied, the supplementary methods for bored piles, and a guide to choosing a method based on the question to be answered A conceptual diagram in three parts. The top part is a gradient arrow bar from left to right, meaning the force applied to the pile increases from integrity checking to load capacity measurement. Below the bar are three cards. Card one, Seismic Integrity Test or Low Strain: a thumbnail of a hand hammer tapping a pile head fitted with an accelerometer, with a wave traveling down and reflecting back; it measures integrity and length, is very fast with several piles per day, is economical, does not evaluate load capacity, suits integrity checks of large numbers of piles, and references DPT 1551-51. Card two, Dynamic Load Test or PDA: a thumbnail of a drop weight in a guide frame striking the pile head, with gauges attached below the pile head wired to the PDA unit and green arrows representing soil resistance; it measures load capacity and integrity, is fast with several piles per day, is much more economical than Static, has high accuracy with CAPWAP analysis, suits confirming the capacity of many piles, and references ASTM D4945 and DPT 1252-51. Card three, Static Load Test: a thumbnail of a jack on the pile head pushing against a beam loaded with kentledge resting on timber cribbing; it measures load capacity directly from real load, is slow with a long time per pile, is costly because kentledge or a reaction system is needed, serves as the reference value, suits calibrating the capacity of a few piles, and references ASTM D1143 and DPT 1251. The middle part shows the supplementary methods for checking the concrete of bored piles without static or impact loading: Cross Hole Sonic Logging or CSL, which sends sound waves between tubes cast into the pile to check the integrity of large-diameter bored piles and references ACI PRC-228.2, and the Coring Test, which drills concrete cores from the pile body to check quality. The bottom strip is choosing by question: to know whether many piles are sound, use Seismic; to confirm that many piles carry the design load, use PDA; for a reference capacity value, use Static on a few piles; and for large bored piles with suspected concrete quality, use CSL or the Coring Test. Speed and cost in the figure are qualitative comparisons, not actual figures. Pile test map: what it measures, force level, how to choose Not to scale 3 main methods · by force on pile Integrity check → capacity 1 Seismic (Low Strain) Light hand-hammer tap Measures Integrity + length Velocity Very fast, many/day Cost Low Load capacity Not assessed Best for: mass integrity checks DPT 1551-51 2 Dynamic Load Test (PDA) High-strain drop weight Measures Capacity + integrity Velocity Fast, many/day Cost Far cheaper than Static Load capacity Via CAPWAP Best for: verifying many piles ASTM D4945 DPT 1252-51 3 Static Load Test Real load in steps Kentledge Measures Direct capacity Velocity Slow per pile Cost High, needs kentledge Load capacity Direct, reference value Best for: calibrating a few ASTM D1143 DPT 1251 Supplementary · bored-pile concrete checks (no static or impact load) Speed/cost = qualitative only Cross Hole Sonic Logging (CSL) Sound waves between cast-in tubes Integrity of large bored piles ACI PRC-228.2 Coring Test Drill concrete cores from pile Bored-pile concrete quality By question Sound? Full length? → Seismic (many) Carries design load? → PDA (several) Need reference value? → Static (a few) Bored pile: poor concrete? → CSL / Coring Test
Pile testing method map — the three main methods arranged by force applied (Seismic · PDA · Static) and the supplementary CSL and Coring Test methods for bored piles. Speed and cost are qualitative comparisons, not actual figures (Image: SPN Soil Engineering)

1) What Can a Seismic Integrity Test (Low Strain) Detect?

The Seismic Test, or Low Strain Integrity Test, checks pile integrity and length but does not measure load capacity. An accelerometer is attached to the pile head, the pile is tapped lightly with a hand hammer, and the reflected wave is measured to see whether there are cracks, reductions in cross-section or abnormal length.

Its strengths are that it is fast, economical and suitable for large numbers of piles, so it is widely used to check piles across a whole project. The main standard is DPT 1551-51; ASTM D5882-16 was withdrawn by ASTM in 2025.

An SPN engineer attaches an accelerometer to a bored pile head and taps it with a hand hammer for a Seismic Integrity Test (Low Strain) on an actual site
Seismic Integrity Test — an SPN engineer taps the pile head with a hand hammer and measures the reflected wave with an accelerometer, quickly checking integrity on many piles at a time (Photo: SPN Soil Engineering)

The limitation is that the Seismic Test does not evaluate load capacity; it only tells whether the pile is sound and approximately how long it is. For details of the method and interpretation, see the article Seismic Test: Pile Integrity Testing (Low Strain)

2) How Does a Dynamic Load Test (PDA) Measure Load Capacity?

The Dynamic Load Test, or PDA Test (named after the Pile Driving Analyzer), evaluates load capacity from the stress waves generated when a drop weight strikes the pile head with a high-strain impact. Strain gauges (Strain Gauge) and accelerometers (Accelerometer) are attached in pairs on opposite sides of the pile below the pile head to record the force and velocity of the wave.

A single test evaluates load capacity, integrity and pile stresses during impact. Its strengths are that it is fast and much more economical than a Static Load Test, with several piles tested per day. Reference standards are ASTM D4945 and DPT 1252-51.

The field data is further analyzed by signal matching (CAPWAP) to evaluate the static capacity and separate shaft friction from end bearing. For the full principles, see Dynamic Load Test (PDA Test), and for how to read the results, see PDA Test result interpretation

3) Why Is the Static Load Test Used as the Reference?

The Static Load Test is used as the reference because it measures load capacity directly from real load, without back-calculating from waves. Load is applied to the pile head in increments with a hydraulic jack pushing against kentledge or a reaction system, and the corresponding settlement is measured. The results are then interpreted using criteria such as the Davisson Method.

Reference standards are ASTM D1143 and DPT 1251. The trade-offs are that it takes a long time, requires a reaction system or kentledge, and is costly, so usually only a few piles in a project are tested.

Kentledge platform of concrete blocks installed above the test pile for a Static Load Test on an actual SPN Soil Engineering site
Static Load Test with a kentledge system — concrete blocks placed on steel beams above the test pile apply real load in increments (Photo: SPN Soil Engineering)

For the method and site preparation, see Static Pile Load Test: Testing Pile Capacity by the Static Method

How Do Seismic, Dynamic (PDA) and Static Tests Differ?

The three methods differ in what they measure, the force level applied, speed and the accuracy of the capacity value. Seismic answers the integrity question, while PDA and Static answer the load capacity question. Summarized in one table:

← Scroll to see the full table →

Table 1: Comparison of the 3 main pile testing methods
TopicSeismic (Low Strain)Dynamic / PDA (High Strain)Static Load Test
MeasuresIntegrity + lengthLoad capacity + integrityLoad capacity (direct)
Force levelLow (hand hammer)High (drop weight)Sustained real load
VelocityVery fast, many/dayFast, many/daySlow per pile
Capacity accuracyCapacity not assessedHigh (with CAPWAP analysis)Direct measurement (reference value)
StandardDPT 1551-51 · ASTM D5882-16 (withdrawn 2025)ASTM D4945 · DPT 1252-51ASTM D1143 · DPT 1251
Best forIntegrity checks on large numbers of pilesConfirming capacity of many pilesCalibrating capacity on a few piles

Which Pile Testing Method Should You Choose?

Choose based on the question you need answered; in practice, several methods are often combined:

  • To check the integrity of large numbers of piles → start with the Seismic Test, as it is fast and economical
  • To confirm load capacity on many piles → use the Dynamic Load Test (PDA)
  • For a reference value of load capacity → select a few piles for Static Load Testing to calibrate
  • For large-diameter bored piles or suspected concrete quality in the pile → consider CSL or the Coring Test in addition

For an in-depth comparison of the two capacity methods, see Dynamic vs Static Load Test: Which One to Choose, and if you have not yet chosen a pile type, see Comparing driven, bored and spun piles

The pile type also affects which methods can be used. Seismic, PDA and Static can be used on both driven and bored piles. CSL requires tubes to be cast into the pile before concreting, so it must be planned before construction, and the Coring Test drills a core through the concrete of a bored pile. Read more about the differences in How testing differs for bored piles and driven piles

The 3D view below shows where the equipment for each method is placed: the Seismic sensor is on the pile head, the PDA gauges are below the pile head, and the CSL probes are lowered into tubes cast into the bored pile.

3D model of a driven pile and bored piles in a soil section, showing where the equipment for the Seismic Test, Dynamic Load Test (PDA), Cross Hole Sonic Logging (CSL) and Coring Test is installed A conceptual 3D view of a soil block cut away to show layers of soft clay, stiff clay and sand, with three piles in a row along the section. The left pile is a square precast driven pile used to show the Seismic Integrity Test or Low Strain: an accelerometer is attached to the pile head, a technician squats and taps it with a hand hammer, and a signal cable runs to the recorder; in the section, wave arrows travel down and the reflection from the pile toe travels back up. The middle pile is a bored pile used to show the Dynamic Load Test or PDA: a guide frame and drop weight sit above a cushion on the pile head, strain gauges and accelerometers are attached below the pile head on two opposite sides and wired to the PDA unit, and green arrows in the section represent shaft friction and end bearing. The right pile is a large-diameter bored pile cut in half to show its interior, with steel Cross Hole Sonic Logging tubes cast in along its full length and projecting above the pile head; transmitter and receiver probes are lowered into the tubes at the same level, dashed lines between the tubes are the sound paths through the concrete, and cables run to the CSL unit. In the center of the same pile head is a Coring Test core hole, with the extracted concrete core lying on the ground. The right panel summarizes five methods: Seismic, sensor on the pile head, measures integrity and length; PDA, gauges below the pile head, measures load capacity and integrity; CSL, probes lowered into tubes cast in before concreting, checks the concrete between tubes; Coring Test, drills a core through the concrete to obtain samples for quality checks; and Static Load Test, jack and settlement gauges at the pile head, measures load capacity directly, which is not shown in this image. A note states that Seismic, PDA and Static can be used on both driven and bored piles, CSL and the Coring Test are for bored piles, and each method is tested separately, not at the same time. 3D model: where each method's equipment goes on the pile Not to scale 1 Seismic on driven pile Accelerometer + hand hammer 2 PDA on bored pile Drop weight hits pile head Strain Gauge + Accelerometer Below head, 2 opp. sides 4 Coring Test Core hole + extracted core 3 CSL in large bored pile Tx–Rx probes in cast tubes CSL unit Soil resistance Skin friction + end bearing Reflection from pile toe Soft clay Stiff clay Sand Where installed · what measured 1 Seismic (Low Strain) Fit: accelerometer on head Meas.: integrity + length 2 Dynamic Load Test (PDA) Fit: gauges below head + weight Meas.: capacity + integrity 3 Cross Hole Sonic Logging Fit: probes in pre-cast tubes Meas.: concrete between tubes 4 Coring Test Do: core through concrete Get: cores for quality check 5 Static Load Test Fit: jack + settlement gauges Meas.: direct capacity (not shown) Applicable pile types Seismic · PDA · Static Both driven and bored piles CSL · Coring → bored piles Conceptual · methods done separately
Equipment location for each method — Seismic places the sensor on the pile head, PDA attaches gauges below the pile head and uses a drop weight, CSL lowers probes into tubes cast into the bored pile, and the Coring Test drills a concrete core (Static Load Test not shown). Conceptual image; each method is tested separately (Image: SPN Soil Engineering)
📋 Number of piles to test

The number of piles to be tested and the methods used should follow the project specification and the judgment of the responsible engineer; there is no fixed formula for every job. See the guidelines in How many piles should be tested, or consult the SPN engineering team to plan testing that suits your project.

Which Standards Apply to Pile Testing?

Pile testing in Thailand references 2 main groups: US ASTM standards and DPT standards of the Department of Public Works and Town & Country Planning. SPN's pile testing follows these standards, and reports are certified by a licensed civil engineer (COE) and can be used for building permit applications:

  • Dynamic Load Test (PDA) — ASTM D4945 and DPT 1252-51
  • Seismic Integrity Test — DPT 1551-51 (ASTM D5882-16 withdrawn in 2025)
  • Static Load Test — ASTM D1143 and DPT 1251
  • Cross Hole Sonic Logging (CSL) — ACI PRC-228.2 (ASTM D6760 withdrawn in 2025)

For the scope of each DPT standard, see DPT pile testing standards: which ones apply

How Much Does Pile Testing Cost?

Starting prices are about THB 100–150/pile for the Seismic Test, about THB 5,500/pile for the PDA Test and about THB 50,000–150,000+/pile for the Static Load Test. Actual prices depend on the number of piles, pile size, test load and site conditions. Reference prices with standards are summarized in one table:

← Scroll to see the full table →

Table 2: SPN reference prices for pile testing services
Test methodStandardStarting priceBest for
Seismic Integrity TestDPT 1551-51 · ASTM D5882-16 (withdrawn 2025)About THB 100–150/pileIntegrity checks on large numbers of piles across a whole project
Dynamic Load Test (PDA)ASTM D4945 · DPT 1252-51From about THB 5,500/pileQuickly confirming the load capacity of many piles
Static Load TestASTM D1143 · DPT 1251About THB 50,000–150,000+/pile, depending on test load and reaction systemCalibrating the reference value of load capacity on a few piles

Note: These prices exclude travel and equipment mobilization, which are charged extra based on the distance to site.

CSL and Coring Test prices depend on pile size and number. Get a free quotation within 24 hrs. For more pricing details for each method, see Pile Testing Prices 2026

📌 Note

This article is provided as engineering knowledge. The choice of test method, number of piles to test, appropriate concrete age and interpretation of results should follow the project specification and the judgment of a licensed engineer.