Drainage Corrugated Drainage Pipe
HDPE double-wall corrugated drainage pipe (Type S) to AASHTO M294 — corrugated outside, smooth inside, solid or perforated, 4"–60" for culverts.
- AASHTO M294
- Type S dual-wall
- 4"–60" · solid / perforated
Prefabricated Horizontal Drain (PHD)
SIGMA prefabricated horizontal drain (PHD) is a band drain made of a mechanically strong polypropylene (PP) core wrapped in a nonwoven geotextile filter jacket, specialised for soil improvement and drainage works. Laid horizontally in the drainage blanket, the PHD collects the pore water discharged by prefabricated vertical drains (PVD / wick drains) installed in soft ground and carries it laterally to an outlet, expediting consolidation of the soft soil without relying on a thick sand drainage layer.
PHD drainPP core + nonwoven filterSoft-ground consolidation
How a prefabricated horizontal drain works
A prefabricated horizontal drain (PHD) improves soft ground by carrying water sideways. Made of a mechanically strong PP core in a nonwoven filter jacket, it is laid horizontally in the drainage blanket above the treated soil, where it collects the pore water discharged through the vertical drains (PVD / wick drains) installed in the soft ground and moves it to an outlet. By giving that water a fast lateral path, the PHD drain expedites consolidation, so the soft soil gains strength and settles in months rather than years.
What the PHD is made of
The drain is a flat band built from two parts. The core is a mechanically strong polypropylene profile whose channels stay open to carry water along the band, and it is wrapped in a nonwoven geotextile filter jacket that lets water in while screening out the soil fines that would otherwise clog the core. Polypropylene makes the band anti-aging and corrosion-resistant, so the PHD keeps working through the months-long preload period without breaking down in the ground.
PHD as a horizontal wick drain
Working as a horizontal wick drain, the PHD replaces the thick granular sand blanket traditionally placed over a PVD field. The PP core stays open under the weight of the surcharge fill while the nonwoven jacket filters fines, so the horizontal drain keeps discharging throughout the preload period. This makes the prefabricated horizontal drain a clean, efficient companion to vertical drains on reclamation, embankment and soft-foundation projects.
Installation in the drainage blanket
The PHD is unrolled and laid out horizontally across the treated area at the level of the old sand blanket, spaced so each band collects the discharge from a group of vertical drains. The bands lead to a collector or outlet at the edge of the fill, and the surcharge or preload is then placed on top. Because the band is prefabricated and light, it is faster and cleaner to lay than importing, spreading and compacting a granular sand layer — and there is no risk of the sand layer silting up.
Where it is used
The PHD is specified on soft-foundation soil improvement and consolidation, preloading and surcharge programs, land reclamation and soft-soil land development — anywhere prefabricated vertical drains are installed and their pore water has to be led away. It is most often a direct replacement for the sand drainage blanket over a PVD-treated site, pairing one for one with the vertical drains it serves.
Specification and pairing
There is no single public statutory standard governing the PHD band drain, so width, core thickness and discharge capacity are product-specific and confirmed against SIGMA production data — discharge capacity is the key property and should be quoted at the actual confining pressure, never guessed. The PHD is normally specified together with the vertical drains it serves: see our wick drain (PVD) for the vertical element, our nonwoven geotextile for related filter fabrics, and the full drainage range for surface collection products.
More views
Key features
- Laid horizontally to collect pore water from vertical drains
- Mechanically strong PP core resists installation crushing
- Nonwoven filter jacket keeps soil fines out of the core
- Speeds soft-ground consolidation as a horizontal wick drain
- Replaces thick sand drainage blankets — faster and cleaner
- Anti-aging and corrosion-resistant for long service life
Ideal for
- Horizontal drainage blanket above PVD-treated soft ground
- Soft-foundation soil improvement and consolidation
- Preloading and surcharge programs
- Reclamation and soft-soil land development
- Replacement for sand drainage blankets
Specifications
Prefabricated horizontal drain (PHD) — manufacturer specification. No single public statutory standard governs the PHD band drain; numeric values to be supplied from SIGMA production data.
| Property | Value | Notes |
|---|---|---|
| Type | Prefabricated horizontal (band) drain | — |
| Core material | Mechanically strong polypropylene (PP) | — |
| Filter material | Nonwoven geotextile jacket | — |
| Color | Black; other colors on request | — |
| Width | On request | band width |
| Core thickness | On request | — |
| Core tensile strength | On request | quote test method |
| Discharge capacity | On request | quote at design confining pressure/gradient |
| Filter — water flow rate / permittivity | On request | ASTM D4491 if reported |
| Roll length | On request | supplied in rolls |
- No single public/statutory product standard was found that governs the prefabricated horizontal drain (PHD) band drain; products are made to manufacturer specifications.
- Width, core thickness, core tensile strength and discharge capacity are product-specific and must be filled from SIGMA own datasheet (with the test method named for each value) before publishing. Discharge capacity should be quoted at the actual confining pressure.
Frequently asked questions
What is a prefabricated horizontal drain (PHD)?
A PHD is a band drain — a mechanically strong polypropylene core wrapped in a nonwoven filter jacket — laid horizontally in the drainage blanket over soft ground. It collects the pore water discharged by the vertical drains (PVD) installed in the soil and carries it laterally to an outlet, speeding consolidation.
How does a PHD differ from a vertical wick drain (PVD)?
Both are PP-core, geotextile-jacketed band drains, but they are installed in different directions. The PVD is driven vertically into the soft soil to give short radial drainage paths; the PHD is laid horizontally above the soil to collect and discharge the water those vertical drains release. They are normally used together.
Can a PHD replace a sand drainage blanket?
Yes — that is its main purpose. A prefabricated horizontal drain works as a horizontal wick drain in place of the thick granular sand blanket usually placed over a PVD field, giving a cleaner, faster installation while still carrying the pore water away during the preload period.
What discharge capacity does the PHD provide?
Discharge capacity is the key design property and falls as confining pressure rises. Because there is no single public standard for the PHD, we confirm width, core thickness and discharge capacity from SIGMA datasheet and quote the discharge at your actual confining pressure — send us the soil profile and surcharge.
What is the price of the prefabricated horizontal drain?
Price depends on the band width, the core thickness and discharge grade, the nonwoven filter jacket and the order quantity. Because the PHD is built to your specification rather than to a single public standard, send us the site area, the required discharge capacity (or soil profile and surcharge) and the length needed, and we will quote a unit price per metre.
What is the minimum order quantity?
The PHD is produced to order with a PP core and a nonwoven jacket, so a minimum order quantity applies and varies with the band width and discharge grade. Tell us the treated area and drain spacing and we will confirm the MOQ in linear metres together with the lead time.
How long is the production lead time?
Lead time depends on the band width, the core and discharge grade and the total length ordered. Once we confirm the width, core thickness and discharge capacity against SIGMA production data, we will give you a firm production and shipping schedule.
How is the PHD packed and shipped?
The band is flat and flexible, so it is supplied in rolls that ship compactly by sea. We confirm the roll length from SIGMA production data, then advise how many rolls fit a pallet or container for your order so you can plan freight — send us the destination port and the total length required.
Request a quote for the Prefabricated Horizontal Drain (PHD)
Tell us quantity, destination port, and any questions — we reply within one business day.
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