Pile Steel Casing: A Practical Guide for Foundation Piling Projects

Pile steel casing is the steel tube placed into a drilled borehole to keep the hole walls from collapsing during bored pile construction. Without it, loose soil and groundwater can cave in at any moment — ruining the pile before concrete is ever poured.

Choosing the right steel casing affects your project schedule, pile quality, and bottom line. This guide covers the types, materials, installation methods, common problems, and cost factors you need to know.

Types of Pile Steel Casing: Single Wall vs Double Wall

Single wall casing has one steel layer. It is lighter, cheaper, and suited for shallow to medium-depth piles in relatively stable soil. Typical diameters range from 600 mm to 2,500 mm, with wall thicknesses of 8–20 mm.

Double wall casing has two concentric steel layers with internal reinforcement ribs. It handles higher torque, resists deformation in hard ground, and is the standard choice for deep piles and full-casing rotary drilling. Wall thicknesses commonly reach 18 mm (outer) / 12 mm (inner) / 8 mm (ribs).

The key differences are straightforward. Single wall casing costs less and works well for shallow to medium-depth piles in stable clay or soft soil, typically reused 20 to 50 times. It is the go-to choice for temporary casing applications. Double wall casing costs 40 to 70 percent more but handles medium to deep piles in cobble, rock, and karst ground. With proper maintenance, double wall casing survives over 100 reuse cycles, making it the standard for full-casing rotary drilling.

A third distinction matters for your budget: temporary casing is removed after concrete pouring and reused on the next pile. Permanent casing stays in the ground as part of the finished pile, typically required in marine or corrosive environments.

Materials and Specifications

Most pile steel casing is manufactured from structural or alloy steel. The grade you choose directly affects torsional strength and wear resistance.

• Q355 — Standard structural steel. Good all-around performance for general piling. Yield strength ≥ 345 MPa.

• 25CrMo — Chromium-molybdenum alloy steel. Higher torsional strength and wear resistance, ideal for double wall casing in hard rock.

• 27SiMn — Silicon-manganese alloy. Excellent hardenability, used for casing joints and drive adaptors subject to repeated impact.

Casing sections come in lengths of 1 to 6 meters, connected by bolted flange joints or button-type male/female joints. The button-type joint is the international standard — it allows quick assembly and works with major rig brands including Bauer, Liebherr, Soilmec, and Casagrande.

Installation: Four Methods and When to Use Each

Installation is where most on-site problems happen. Here are the four standard methods:

1. Vibratory installation — A vibratory hammer drives the casing into the ground. Fast and efficient for sandy and soft soils. Noise and vibration levels are moderate. Not suitable for dense rock layers.

2. Oscillator / rotator installation — A hydraulic oscillator grips and rotates the casing into the ground with high torque. Best for hard ground, cobble layers, and urban sites where low vibration is required. This is the primary method for full-casing rotary drilling.

3. Impact hammer driving — Uses a diesel or hydraulic hammer to drive the casing. Simple and powerful, but high noise and vibration make it less common in urban areas.

4. Hydraulic jacking — Pushes the casing down with hydraulic force. Used for limited-headroom sites where other rigs cannot operate.

The general procedure is straightforward: position the casing over the borehole, check verticality with a spirit level (deviation must not exceed 75 mm at cut-off level), drive or rotate the casing to the required depth, drill out the soil inside, lower the rebar cage, pour concrete, and extract the temporary casing while concrete is still fluid.

Common Problems and How to Prevent Them

Joint failure during rotation is usually caused by worn bolts or misaligned joints. Inspect bolts every 50 cycles and replace them at 10 percent wear to prevent this.

Casing deformation or buckling happens when you drive into rock without pre-drilling. Always pre-drill a pilot hole 50 to 100 mm smaller than the casing outer diameter.

Verticality deviation results from unstable ground or a rushed setup. Use a guide casing and check verticality every 2 meters of advance.

Difficulty extracting casing occurs when concrete sets too fast or friction locks the tube. Pour concrete in one continuous operation and start extraction within 30 minutes.

Soil collapse inside the casing is caused by water ingress through worn joints. Seal joints with rubber rings and inspect wall thickness each month.

These issues are preventable. Most casing failures trace back to skipped maintenance, not material defects.

What Affects the Price of Pile Steel Casing

No competitor publishes pricing — so here is what actually drives cost:

• Material grade: 25CrMo costs 25–40% more than Q355, but lasts 2–3 times longer in abrasive ground.

• Diameter and wall thickness: Larger diameter and thicker walls mean more steel per meter.

• Joint type: Bolted flange joints are cheaper to manufacture; button-type joints cost more but save labor on site.

• Surface treatment: Anti-corrosion epoxy or galvanizing adds 8–15% to the unit price but extends service life in marine environments.

• Quantity: Orders above 50 sections typically qualify for 5–10% volume discounts.

Total cost of ownership tip: Double wall casing costs more upfront but survives 100+ reuse cycles versus 20–50 for single wall. Over a multi-pile project, double wall often costs less per pile.

How to Choose a Pile Steel Casing Supplier

Use this 6-point checklist before placing an order:

1. Manufacturing capability — Ask for photos of their CNC machining and welding lines. Casing joints require precision machining; backyard workshops cannot guarantee tolerances.

2. Certifications — Minimum: ISO 9001. For export to the EU or Middle East, look for CE marking or EN 10210 compliance.

3. Rig compatibility — Send your rig model (Bauer BG-28, Liebherr LB 36, etc.) and ask for a compatibility confirmation in writing.

4. Delivery time — Standard sizes ship in 15–25 days. Custom diameters may take 35–45 days. Get it in the contract.

5. After-sales support — Ask whether they provide on-site technical guidance for first-time installation. Reputable manufacturers do.

6. References — Request 2–3 recent project references. If they cannot provide any, walk away.

Conclusion

Pile steel casing is not a commodity. The right type, material, and installation method determine whether your bored piles meet design capacity or fail inspection. Choose the correct steel grade for your soil, follow proper installation procedures, and select a qualified supplier to avoid costly piling failures.

If you need custom pile steel casing manufactured to your project specifications, [contact our engineering team] for a free consultation.

Frequently Asked Questions

Can pile steel casing be reused? Yes. Temporary casing is designed for reuse — single wall 20–50 cycles, double wall 100+ cycles with proper maintenance.

How deep can pile steel casing go? With segmental double wall casing and a hydraulic oscillator, depths of 50–80 meters are achievable. Single wall is typically limited to 20–30 meters.

What steel grade is best for pile casing? Q355 is sufficient for general piling in clay and sand. For rock layers or full-casing drilling, 25CrMo alloy steel provides the torsional strength needed for long service life.