Steel Sheet Pile

• Specification

• Process

• Tests

• Packing & Delivery

1. Hot Rolled vs Cold Formed: Which sheet pile type suits my project?

Hot rolled sheet piles are produced from steel blooms at temperatures exceeding 1000°C, resulting in uniform wall thickness across the entire cross-section. The Larssen interlock is continuously fusion-welded at the factory, ensuring superior watertightness with permeability rates below 1×10⁻⁵ cm/s under standard driving conditions.

Cold formed sheet piles are manufactured by progressive bending of hot-rolled coils at ambient temperature. Wall thickness varies from 5mm at the web center to 8mm at flange edges. Interlock integrity depends on cold work hardening; no welding is applied to the interlock seam.

Application selection: Permanent marine structures (harbor walls, seawalls, cofferdams), critical water-retaining structures, and projects requiring driving through hard strata mandate hot rolled sections. Temporary earth retention, cut-off walls for basement excavations, and short-term cofferdams with scheduled removal favor cold formed for economic reasons.

2. How do I select the optimal section modulus and interlock type?

Section modulus selection follows Eurocode 3 or ASTM A328 design procedures. Calculate maximum design bending moment from soil pressure distribution (at-rest or active earth pressure coefficient depending on wall displacement). Divide allowable stress (typically 0.65×yield for temporary works, 0.50×yield for permanent) into design moment to obtain required section modulus.

U-shaped sections (PU, PU-R, AU series) provide symmetrical interlock geometry ideal for circular cofferdams and axisymmetric structures. Z-shaped sections (AZ, HZ-A, ZX series) offer higher section modulus per meter of wall width due to neutral axis separation, making them economical for cantilever and anchored walls.

Interlock selection: Larssen (socket) interlock provides positive water seal but limits angular deflection to 3° per pile. Ball-and-socket interlock permits 5-7° deflection, essential for curved walls with radii below 30m. Combined interlock (free-clutching) allows rapid driving without initial positioning accuracy—preferred for temporary works where speed dominates.

3. What steel grades and coatings ensure corrosion durability?

Base steel: S270GP to S460GP per EN 10248 (yield strength 270-460 MPa). ASTM A328 governs US market with minimum yield 45 ksi (310 MPa). Corrosion rate in atmospheric exposure averages 0.1mm/year in temperate climates; marine splash zones experience 0.3-0.5mm/year.

Protective systems: Shop-applied bituminous coating (600μm DFT) for buried sections. Epoxy coating systems (400-800μm DFT) for splash zone immersion. Hot-dip galvanizing (85μm minimum) for atmospheric service. Concrete encasement over critical zones provides 50+ year service life.

For permanent marine installations, specify cathodic protection compatibility. High-strength low-alloy (HSLA) grades like ASTM A572 Grade 50 offer 30% thickness reduction for equivalent corrosion allowance, offsetting material premium with fabrication and handling savings.

4. How do driving method and soil conditions affect installation?

Impact hammering (5-15 ton ram): Applicable for stiff clays, dense sands, and stratified soils with gravel layers. Energy transfer efficiency 60-80%; requires follower cap to protect pile head. Maximum practical depth 40m in cohesive soils. Pre-augering recommended when N-values exceed 50 blows/300mm.

Vibratory driving (30-150kN eccentric moment): Effective in loose to medium-dense granular soils, non-cohesive fills. Near-zero effective stress zones achieve highest installation speed (0.5-2m/min). Cohesive soils with undrained shear strength exceeding 80kPa cause diminishing returns. Noise and vibration levels require monitoring within 30m of sensitive infrastructure.

Jetting assistance: 20-50mm water jet at 2-5 bar accelerates penetration through sandy strata. Prevents clogging of Larssen interlock in water-saturated conditions. Combined with vibratory driver reduces total driving time by 30-50% in favorable geology.

5. What tolerances govern dimensional accuracy and wall alignment?

Per EN 12063 and ASTM D38, standard tolerances: verticality ±2% of exposed length for cantilever sections, ±1% for anchored walls. Horizontal alignment ±75mm from design centerline. Interlock cleanliness mandatory—compressed air cleaning of engaged seams before each pitch prevents grit infiltration and driving obstruction.

Interlock continuity verification: Leak-off test using air pressure (0.5 bar) injected between sealed pair of interlocks. Sustained pressure indicates intact sealing; pressure decay signals interlock damage requiring pile extraction and replacement.

6. What documentation and third-party inspection options are available?

EN 10204 Type 3.1 mill test certificates mandatory: heat chemistry (C, Mn, Si, P, S ≤ limits per grade), tensile testing (yield, UTS, elongation), bend test for plates under 16mm. Dimensional inspection per EN 10248-2: thickness -5%/+10%, width ±50mm, length +125mm/-0mm.

Third-party inspection agencies (SGS, Bureau Veritas, DNV, Lloyd's Register) available for witness inspection at mill and pre-shipment. Inspection scopes include: material verification, dimensional check, visual examination for surface defects, interlock geometry measurement using go/no-go gauges.

Special documentation: CE marking per EN 1090-1 for permanent works in EU. NACE MRO175/ISO 15156 compliance documentation for H₂S service in oil/gas applications. Corrosion data reports for marine environment exposure assessments.