SY390 U-type sheet pile is a U-shaped sheet pile rolled to the SY390 grade of JIS A 5528, with a minimum yield strength of 390 MPa. When used for temporary support, its higher grade can carry the earth and water pressure of the excavation, allowing a lighter section to do the job. This provides high-strength temporary support for deep excavation, cofferdams, and waterside works.
What Is the SY390 U-Type Sheet Pile?
SY390 U-type steel sheet pile is a U-shaped sheet pile hot-rolled to the SY390 grade of JIS A 5528. It is an open, symmetrical U-shaped section with a formed interlock extending the full length along each of its two vertical edges; when one pile is set beside the adjacent pile the interlocks engage, and the whole row is driven into a continuous wall that retains both soil and water.
In the designation SY390, "SY" stands for steel and yield, and "390" is the guaranteed minimum yield strength - 390 MPa. The U-shaped section determines the shape the wall takes; the grade determines how much earth and water pressure that shape can carry.
Mechanical properties (per JIS A 5528)
| Property | Value |
|---|---|
| Yield strength | 390 MPa min. |
| Tensile strength | 490 MPa min. |
| Elongation | 16% min. |
Chemical composition (representative limits)
| Element | C | Si | Mn | P | S | Cu | Ni | Cr | Mo |
|---|---|---|---|---|---|---|---|---|---|
| Max. content (wt%) | 0.22 | 0.55 | 1.60 | 0.040 | 0.040 | 0.35 | 0.30 | 0.30 | 0.10 |
Representative limits for the SY390 grade; the full composition of the supplied heat is stated on the mill certificate.
Why Choose SY390 U-Type Piles for Temporary Support?
Higher Load per Unit Section. The 390 MPa grade carries temporary earth and water pressure with a lighter section, or completes the work in a shorter period before the permanent works are finished.
Retains Both Soil and Water. The closed interlocks retain water as well, reducing or eliminating the need for separate dewatering during the temporary stage.
Extract and Reuse. The piles are pulled out and reused at the end of the stage, spreading the initial cost across stages, projects, and rentals.
Suited to Temporary Forms. It works as cantilever, internally braced, or anchored, with section and grade matched to the standard on which the quotation is based.
Applications of SY390 U-Type Sheet Piles in Temporary Works
Building Basement and Foundation Excavation - supported by a temporary earth-retaining wall around the pit until the basement is cast.
Municipal and Utility Trenches - the wall retains soil on the excavation side, then is extracted after the pipe or utility gallery is laid and backfilled.
Cut-and-Cover Tunnels, Station Pits, and Other Shallow-Buried Works - keeping the ground open during construction of the structure below.
Structural Deep Excavations - such as pump-station houses, lock chambers, or pier foundation pits; the deepest parts are supported by internal bracing rings or tieback anchors.
Structural Efficiency of SY390 U-Type Sheet Piles in Temporary Works
The SY390 grade raises the allowable stress of the section, so the wall satisfies the stage-limited loads with a lighter section than a normal grade, and is recovered for reuse when the stage ends.
| Loading case | Effect of the SY390 grade | Benefit to the works |
|---|---|---|
| Sustained earth and water pressure | Higher allowable stress per section | Reduced section mass |
| Deep excavation and deep trench | Free-standing, braced, or anchored wall | Large-scale extraction for reuse |
| Groundwater during the stage | Watertight interlock retained | Dewatering reduced or omitted |
| Multi-phase or cross-project use | Driven, extracted, redriven | First cost spread over phases |
Grade and Standard Selection
For temporary support the SY390 grade of JIS A 5528 is quoted, or its equivalent under GB/T 20933 or EN 10248 where the job is specified to those standards. The section is chosen for the temporary earth and water pressure, the grade for how much of that pressure the temporary wall must carry, and the length for the excavation depth and the embedment the temporary wall requires.
| Standard | Grade (yield) | Use in temporary works |
|---|---|---|
| JIS A 5528 | SY390 | Temporary walls under high earth and water pressure |
| GB/T 20933 | Q390P | Equivalent where the job is to the Chinese standard |
| EN 10248 | S390GP | Equivalent where the job is to the European standard |
Construction of SY390 U-Type Sheet Piles for Temporary Support
The temporary cycle is driving, extracting, and reusing. Each stage is set out below.
| Stage | Construction operation | Control point in the works |
|---|---|---|
| Driving | Place and drive each pile to the design depth in sequence | Interlock closure and low cumulative deviation |
| Extraction | Reverse driving from the last pile back along the run | Each interlock releases without distorting the line |
| Reuse | Inspect, then re-run the same set to the next excavation | Interlock condition governs re-use on site |
As a U-type steel sheet pile supplier, we supply the same product for both permanent and temporary works. We supply the SY390 grade in the section and pile length required by the temporary wall, rolled to the applicable specification and verified against the mill certificate, with surface and interlock treatment matched to the pile's driving and extraction method.
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FAQ
Why use the higher-yield SY390 grade for temporary support?
Because a temporary wall is required to carry its load for a short time: the higher grade lets a lighter section carry the temporary earth and water pressure, reducing material and handling and shortening the support period.
How often can the pile be reused?
Reuse depends on the service the pile has seen and the care in driving and extraction; a well-drilled, well-handled pile is routinely reused across several stages or projects before its profile is spent.
Can the pile hold water in a temporary stage?
Yes. The closed interlock retains water as well as soil, so a temporary support can also reduce or remove the need for separate dewatering.
Can the temporary pile be fully extracted?
In ordinary ground a pile driven for support is extracted cleanly and checked for reuse; the decision to withdraw and the extent of withdrawal depend on the ground and the temporary scheme.
What must a temporary-support quotation confirm?
Confirm the section and length for the excavation depth, the grade SY390 or its equivalent, the governing standard, the sequent method (cantilever, braced or anchored), quantity, and the extraction-and-reuse arrangement.