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Overburden Casing System

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Concentric overburden casing drilling system to borehole for anchoring
Concentric overburden casing drilling system to borehole for anchoring
Concentric overburden casing drilling system to borehole for anchoring
Concentric overburden casing drilling system to borehole for anchoring

Concentric overburden casing drilling system to borehole for anchoring

Different name:Symmetric casing system
Main application:forfoundation piling, micro piles, water well drilling, geothermal well drilling.
Core specification parameters:Diameter 114-406mm
Applications:Widely used inmedium mini-type grouting hole of building,water-well drilling , geothermal drilling, solar and construction/geotechnical drilling projects
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Once bore a hole in the unstable soil formation, there is potential risk of hole collapsing. Casing drilling is an ideal drilling method that combine the drilling and casing process together to stabilize the hole. Powered by DTH hammer, the casing system has a pilot bit which drives a ring bit to drill a hole wide enough so that a casing tube can slide down to the hole. As the drilling process and casing process are performing at the same time, the casing tube can stabilize the hole immediately.

Overburden casing drilling system can be classified into concentric casing system, eccentric casing system and slide block casing system.

Concentric casing system also called symmetric overburden casing system, it can drill a hole at any angle (including horizontal) and the hole depth can be up to 100m. Concentric overburden casing system is composed of a central pilot bit, ring bit (reamer), casing shoe

concentric casing system

The central pilot bit is attached to the DTH hammer and the casing shoe is welded to the casing tube. Powered by the DTH hammer, the central pilot bit drives the ring bit to drill a hole large enough and meantime the casing tube slide down to stabilize the hole. Once drilling the hole into the required depth, unlock the pilot bit by reverse rotation of the drilling string and then pull out the pilot bits through the casing tube. As for the ring bits and casings, they can be left in the hole for the permanent casing system or can be retrievable for the retrievable casing system.

  • Drilling a hole straight and fast, even drilling in the gravel, sand, pebble formation;

  • Requiring less torque of the rig, even the drilling rig with small torque can drill a large hole;

  • It’s easy to unlocking and relocking the concentric casing system due to its simple structure;

  • Drilling a straight hole at any angle;

  • It’s easy to operate and cost-effective

Casing Tube

We have a range of casing tube from diameter 108mm to 377mm for concentric/ eccentric casing system.


ModelCasing tube OD (mm)Max OD of pilot bit (mm)Max OD of reamer bit(mm)DTH Hammer type
114mm concentric casing11494126Cop34/DHD3.5 hammer
127mm concentric casing127107138Cop34/DHD3.5 hammer
140mmconcentric casing140118154Cop44/DHD340/SD4/QL40 hammer
146mmconcentric casing146124158Cop44/DHD340/SD4/QL40 hammer
168mmconcentric casing168146184Cop54/DHD350/SD5/QL50/M50 hammer
178mmconcentric casing178157194Cop54/DHD350/SD5/QL50/M50 hammer
183mmconcentric casing183160198Cop54/DHD350/SD5/QL50/M50 hammer
194mmconcentric casing194178208Cop64/DHD360/SD6/QL60/M60 hammer
219mmconcentric casing219203234Cop64/DHD360/SD6/QL60/M60 hammer
245mmconcentric casing245217260Cop84/DHD380/SD8/QL80 hammer
273mmconcentric casing273246291Cop84/DHD380/SD8/QL80 hammer
325mmconcentric casing325297340Cop84/DHD380/SD8/QL80 hammer
377mm concentric casing377351405DHD112/SD12/QL120/NUMA120
Place of Origin:Made in China
Model Number:Concentric casing system
Certification:COC/PVOC/FORM E/CO/ISO 9001
Minimum Order Quantity:1PCS
Packaging Details:Wooden cases
Delivery Time:10working days
Competitive Advantage

High drilling efficiency

Due to its good performance of high penetration rate and minimal deviation tendency, ourDown-the-hole drilling toolshave been exported to many different countries such as USA, South Africa, Ireland etc and won a good feedback.

Quality assurance

With many years experiences of production of Down-the-hole drilling tools, the concentric casing system we made have long service life and lower air consumption.

All around after-sales service

Our sales will response to any questions within 24 hours once we get. We pay great attention to the feedback from clients and satisfy them both on products and services.


The warranty period is six months since the casing system are delivered.


1. What is a Concentric Overburden Casing Drilling System?

A Concentric Overburden Casing Drilling System is a specialized drilling method used in challenging ground conditions. It involves a simultaneous drilling and casing process, allowing for efficient penetration through overburden layers while maintaining borehole stability.

2. How does the Concentric Overburden Casing System work?

This system uses a concentric drill bit, where the outer part drills the overburden and the inner part drills the rock or soil. As drilling progresses, casing pipes are simultaneously advanced to stabilize the borehole.

3. What are the key components of this system?

The system includes a concentric drill bit, casing pipes, a casing shoe, and often a hammer or drilling rig adapted for this technique.

4. In what types of projects is this system used?

It's commonly used in construction projects requiring foundation work in unstable ground, such as building foundations, bridge supports, and in water well drilling.

5. What advantages does the Concentric Overburden Casing System offer?

The system provides efficient drilling in mixed ground conditions, minimizes borehole collapse, and allows for quicker installation of casings in unstable soils.

6. Can this system handle drilling in water-saturated soils?

Yes, it's particularly effective in water-saturated or loose soils, as the casing installation prevents borehole collapse and water ingress.

7. Are there different sizes and types of concentric systems?

Yes, there are various sizes and designs available, tailored for different drilling conditions and project requirements.

8. What kind of maintenance does this system require?

Regular maintenance includes inspecting and cleaning the drill bits and casing shoes, as well as ensuring the compatibility and condition of all components.

9. How does this system compare to traditional drilling methods?

The Concentric Overburden Casing System is more efficient in unstable ground conditions compared to traditional methods, offering greater safety and stability.

10. Is specialized training required to operate this system?

Operating this system effectively requires specific training, particularly in handling the equipment and understanding the mechanics of simultaneous drilling and casing.

11. Can the components of this system be reused?

Many components, like the casings and drill bits, are reusable, depending on their condition post-operation. Regular maintenance extends their usability.

12. How does the use of this system impact the overall drilling cost?

While the initial investment in this system might be higher, it can lead to cost savings through reduced drilling time, minimized collapse risks, and the potential for reusing components.