Steel Sheet Pile Testing

Steel sheet pile inspection mainly conducts scientific testing and analysis on the appearance and dimension testing, material chemical composition analysis, mechanical property testing, interlock testing, coating property testing and welding quality testing, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Appearance and dimension testing: The comprehensive visual inspection is carried out on the steel sheet piles, identifying whether the surface has the defects such as the cracks, laminations, folds, corrosion and deformations. At the same time, the tools such as the callipers, micrometers and ultrasonic thickness gauges are used to precisely measure the key dimensions such as the lengths, widths, thicknesses, web heights and flange widths, ensuring that they meet the allowable tolerance ranges of the design drawings and product standards (such as EN 10248).

Material chemical composition analysis: Through the sampling and the fast and accurate element quantitative analysis with the spectrometers (such as the direct-reading spectrometers), verifying whether the contents of the main and residual elements such as the carbon (C), silicon (Si), manganese (Mn), phosphorus (P) and sulfur (S) of the steel used for the sheet piles meet the provisions of the relevant standards (such as ASTM A572 and JIS G3192). This is the basis of guaranteeing their mechanical properties and welding properties.

Mechanical property testing: This is the core of evaluating the load-bearing capacities and toughness of the steel sheet piles. The main testing items include the tensile testing (determining the yield strength, tensile strength and elongation after fracture), Charpy V-notch impact testing (determining the impact absorption energy at the specified temperatures, evaluating the low-temperature toughness), as well as the bending testing (inspecting the plasticity and surface qualities of the steel), ensuring that they can meet the stress requirements in the engineering environments.

Interlock testing: The interlocks are the key parts of the continuous engagement of the steel sheet piles to form the continuous walls. The testing contents include the tolerance measurement of the interlock shapes and dimensions, the internal finish inspection of the interlocks, as well as the interlock engagement testing (full-length inspection), ensuring that the adjacent pile bodies can be smoothly and tightly engaged with each other, forming the effective water-tight or soil-tight barriers.

Coating property testing (if applicable): For the steel sheet piles with the anti-corrosion coatings (such as the epoxy resins and polyurethanes), the coating thicknesses (using the coating thickness gauges), adhesion (cross-cut method or pull-off method), hardness and chemical corrosion resistance need to be tested. These tests ensure that the coatings can effectively protect the base materials during the transportation, pile driving and service processes, extending the service lives.

Welding quality testing (for the welded piles): For the steel sheet piles welded from the multiple components, the strict testing needs to be carried out on the welds. Including the weld appearance inspection (no defects such as the cracks, lack of fusion and undercuts), non-destructive testing (such as the ultrasonic flaw detection or magnetic particle flaw detection to find the internal defects), as well as the welding procedure qualification, ensuring that the weld strengths match the base materials.

Testing Scope

New pile pre-delivery inspection: The comprehensive quality inspection carried out after the production of the steel sheet piles and before the delivery, covering all the above testing items. This is the first gate of the quality control, aiming to ensure that the products meet the requirements of the purchase contracts, design specifications and the relevant international/national product standards, and to issue the ex-factory certificates and test reports.

Incoming acceptance testing: The re-inspection carried out by the construction parties, supervision parties or third-party testing institutions after the steel sheet piles arrive at the construction sites. Usually in the form of the sampling inspection, emphatically re-checking the appearance dimensions, interlock qualities and material certificate documents, etc., preventing the pile materials damaged during the transportation or with the batch discrepancies from being used in the projects. It is the important link of the construction quality control.

In-service and reusable pile testing: For the old steel sheet piles pulled out from the completed projects and planned to be reused, the testing is crucial. The wear and deformation conditions of their interlocks, the straightness, corrosion and damage degrees of the pile bodies, as well as the potential degradation of the mechanical properties need to be emphatically evaluated, to judge whether they meet the safe use requirements of the new projects.

Special environment application testing: For the steel sheet piles used under the special working conditions such as the corrosive environments (such as the seawater and industrial polluted soils), low-temperature environments or dynamic loads (such as the docks and breakwaters), the special testing needs to be added. For example, the stricter low-temperature impact testing, corrosion rate evaluation or fatigue property testing, to ensure their long-term reliability under the harsh conditions.

Process quality control testing: The synchronous testing carried out during the pile driving construction processes of the steel sheet piles, mainly including the verticality monitoring, pile top elevation control, interlock engagement tightness inspection, as well as the observation of the wall leakage conditions after the foundation pit excavation. This type of testing aims to timely correct the construction deviations and guarantee the overall effectiveness of the support structures or water-stop curtains.

Pile body integrity testing: For the steel sheet piles serving as parts of the permanent structures (such as the permanent retaining walls and basement walls), after the construction or after a period of use, the technologies such as the low strain reflection wave method or ultrasonic transmission method can be adopted to test whether the pile bodies have the internal defects such as the fractures, severe deformations or interlock disengagement, evaluating their structural integrity.

Testing Methods

Visual inspection and dimension measurement: The most basic and necessary testing method. The inspectors use the lighting tools, magnifying glasses, etc., to carry out the systematic observation of the full surfaces of the steel sheet piles according to the standards. The dimension measurement uses the calibrated steel tapes, vernier callipers and outer diameter micrometers, etc., carried out at the specified measurement points and compared with the tolerance tables. For the complex cross-sections, the dedicated gauges or templates are often used for the comparison.

Physical and chemical analysis testing method: Used to determine the material compositions and properties. The chemical composition analysis mainly adopts the spark direct-reading spectrometry (OES) or X-ray fluorescence spectrometry (XRF). The mechanical property testing needs to carry out the tensile and bending testing on the universal material testing machines, and the Charpy impact testing on the impact testing machines. All the specimen preparation, test environments and rates strictly follow the provisions of the ASTM, ISO or GB/T standards.

Non-destructive testing technology: Detecting the internal or surface defects of the inspected objects without damaging them. The ultrasonic testing (UT) is often used to detect the internal delamination, inclusions and weld internal defects of the steel plates; the magnetic particle testing (MT) or penetrant testing (PT) is sensitive to the surface and near-surface cracks, often used for the interlock areas and weld surface inspection.

Coating testing method: The coating thicknesses are often measured with the magnetic thickness gauges (iron-based) or eddy current thickness gauges (non-iron-based). The adhesion testing often uses the cross-cut method (ISO 2409) or the more quantitative pull-off method (ISO 4624). The chemical resistance is evaluated by immersing the coating specimens in the specific solutions for a period of time and then observing their appearance changes.

Interlock functional testing: Usually adopting the "full-length inspection" method, i.e., a standard interlock connector (or the interlock of another pile) is trial-inserted along the entire interlock length of the inspected pile, checking whether it can pass smoothly without the jamming, thereby qualitatively evaluating whether the shape tolerances, straightness and internal cleanliness of the interlocks meet the engagement requirements.

On-site fast testing technology: For the construction site needs, such as using the Leeb hardness testers to quickly infer the steel strengths, using the corrosion scanners to evaluate the corrosion conditions, and using the total stations or inclinometers to monitor the verticality during the pile driving processes. These methods can provide the immediate data support for the on-site decisions.

Testing Standards

Domestic Standards:

1. GB/T 228.1-2021, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

2. GB/T 229-2020, Metallic materials — Charpy pendulum impact test method

3. GB/T 232-2010, Metallic materials — Bend test method

International Standards:

1. EN 10248, Hot rolled sheet piling of non alloy steels

2. ASTM A572, Standard specification for high-strength low-alloy columbium-vanadium structural steel

3. JIS G3192, Dimensions, mass and permissible variations of hot rolled steel sections for general structure

4. ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

5. ISO 148-1, Metallic materials — Charpy pendulum impact test — Part 1: Test method

6. ISO 2409, Paints and varnishes — Cross-cut test

7. ISO 4624, Paints and varnishes — Pull-off test for adhesion

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Dimension and geometric quantity measurement equipment: Including the high-precision steel tapes, vernier callipers, outer diameter/plate thickness micrometers, ultrasonic thickness gauges (used to measure the remaining thicknesses of the installed piles), radius templates, straightness inspection rulers (or wire-pulling method tools), as well as the total stations or laser trackers for the large-size measurement, ensuring the precise control of the dimension tolerances.

Chemical composition analysis instruments: The portable or bench-type direct-reading spectrometers are the main equipment of the fast composition analysis on site and in the laboratories. The laboratories can also use the more precise carbon-sulfur analysers and inductively coupled plasma optical emission spectrometers (ICP-OES) for the trace element analysis. The handheld XRF analysers are suitable for the fast material designation identification and screening on site.

Mechanical property testing machines: The electronic universal material testing machines are used to carry out the tests such as the tensile, bending and compression, which can automatically record the load-displacement curves. The pendulum impact testing machines are used to carry out the Charpy V-notch impact testing at the specified temperatures. These equipment need to be regularly verified by the metrology institutions, ensuring the accuracy of their forces, speeds and temperatures.

Non-destructive testing equipment: Including the digital ultrasonic flaw detectors (equipped with the probes of the different angles), magnetic particle flaw detection machines (including the magnetic yokes, magnetic particles and UV lamps) and dye penetrant testing reagent kits. The advanced phased array ultrasonic testing (PAUT) equipment can carry out the more precise imaging testing of the welds with the complex geometric shapes.

Coating testing instruments: The magnetic/eddy current coating thickness gauges, cross-cut testers (with the cutting blades), pull-off adhesion testers, pencil hardness testers, gloss meters, as well as the salt spray test chambers (for the laboratory accelerated corrosion testing), etc., constituting a complete set of coating property evaluation tools.

Dedicated testing tools and auxiliary equipment: Such as the standard connectors or trial bars for the interlock full-length inspection, Leeb or Webster hardness testers for the on-site hardness testing, feeler gauges for checking the pile body straightness, endoscopes for the internal defect positioning, as well as the digital cameras, marking pens and standardized record forms needed for recording the testing data.