Today, drilled casings are one of the most popular methods for foundations, reinforcement work, and well drilling. They especially lend themselves to urban work such as bridge, utility line, wharf, and building construction.
In fact, with the development of DTH drilling and the introduction of special drilling systems like Symmetrix, casing advancing in overburden has become more refined.
A multitude of applications
Over the years Atlas Copco overburden drilling systems have opened a multitude of new business opportunities for contract drillers worldwide. Here's a presentation of a few of them.
Well drilling - Symmetrix is ideal for casing water wells and geothermal wells. Symmetrix can also be used for oil and gas wells as well as to drill conductor casings.
Suitable overburden system - Symmetrix can be used depending on the size and depth of the surface casing pipe.
Exploration drilling - An ideal method of supporting exploration holes when bulk sampling or diamond core drilling. Even popular in seismic drilling and in start casings for other forms of exploration.
Suitable overburden system - Both retrievable and non-retrievable casings.
Curtain grouting - Symmetrix is used in drilling preholes for curtain grouting to form a non-permeable underground wall structure.
Suitable overburden system - Retrievable casings.
Symmetrix - a revolution in casing advancement
Symmetrix is a truly revolutionary product. Not only is it an all-round multipurpose concentric drilling system, it also has opened the way for engineering consultants to utilize new construction methods that save contractors time and money, not to mention offer new business opportunities.
Can drill through almost any ground condition - Thanks to its concentric system, Symmetrix can drill through almost any ground condition. Whether there's sand or boulders, Symmetrix drills on until the required depth is reached.
Not only a product--it's a drilling concept - Over the past 10 years Symmetrix has replaced many other methods, such as auger drilling, pile drilling, etc. Its simplicity and efficiency have opened many engineering consultants' eyes to alternative methods for foundations and reinforcement work. Today this product is used in micropiling, underpinning, anchoring, tunneling, marine work, and horizontal drilling - to name a few. All this work can be carried out quicker and deadlines made tighter.
Straighter and faster - When piling, it's imperative that the casing pipe is drilled at exactly the right angle. Any slight deviation means the supporting capabilities are weakened. That's where Symmetrix is outstanding. With no extra reaming wings, the concentric drill heads drive straight through any obstacles without straying from its goal. And thanks to the optimum drill bit design, the job is done quickly and efficiently.
From DTH rigs to cranes - Symmetrix is highly flexible and can be used on a wide range of drill rigs, the most common being DTH rigs. When very long casings are needed, cranes can be easily adapted to use DTH hammers. And as Symmetrix requires less torque than other overburden drilling systems, smaller rigs such as exploration and tophammer rigs can be used with excellent results.
Working Principle
The casing shoe is welded to the casing. The pilot bit and ring bit are locked together by the bayonet coupling.Together they drill a hole large enough to allow the casing to be pulled into the hole. The pilot bit and ring bit rotate with the drill string while the casing shoe and casing do not rotate.
After reaching bedrock, the pilot bit is unlocked by a slight reverse rotation of the drill string. The drill string and pilot bit are then retrieved through the casing. A standard bit is installed in the hammer and drilling continues.
A unique concentric drill bit design - Symmetrix consists of three main components:
A pilot bit that drills and guides the drillstring.
A casing shoe that's welded onto the casing pipe.
A ring bit that, together with the pilot bit, drills the hole and makes room for the casing to advance down the hole.
There are three different types of ring bit and casing shoe assemblies:
A solitary ring bit with no connection to a casing shoe.
A welding ring that holds a ring bit and casing shoe together.
A factory assembled ring bit set with integrated ring bit and casing shoe.
The pilot bit locks into the ring bit and commences drilling, while the casing pipe is pulled down by the pilot bit's casing shoe shoulder. Once the hole is finished, drilling rotation is reversed, the pilot bit is released and removed, leaving the casing pipe in place.
Highly versatile
Symmetrix can be used in a multitude of applications, handling casings from 3" to 48" (76 to 1220 mm) to almost any depth. There are six standard models.
End-bearing piles - A common method of piling where the casing is drilled into a rock socket, using Symmetrix with non-retrievable ring bits. Ideal for drilling 4-1/2" to 48" (114 to 1220 mm) casings. A welding ring option is available from 219 mm casings while ring bit sets are available from 5-1/2" to 7-5/8" (139 to 194 mm) casings.
Skin friction piles - In this method, drilling casings are pulled out after concrete is poured in. The pile is caseless, utilizing the uneven contact between the ground and the poured cement slurry. Retrievable Symmetrix with ring bit sets are used for casings from 3-1/2" to 48" (89 to 1220 mm).
Well drilling casings - This type of equipment is ideal for water and geothermal wells. Here, the casing is drilled and cemented into the rock socket with non-retrievable Symmetrix. A DTH bit is then used to drill the well. Ideal for drilling 5-1/2" to 36" (139 to 914 mm) casings.
Symmetrix with drill-through pilot bit - This Symmetrix system is ideal for making short rock sockets with the pilot bit. This is available in retrievable and non-retrievable versions.
Horizontal drilling - This specialized Symmetrix system is for horizontal drilling and break-through drilling. The ring bit is recoverable. Available for drilling 5-1/2" to 48" (139 to 1220 mm) casings.
Tophammer rigs - As tophammer rigs are very common, Symmetrix also has been adapted to fit these rigs. Tophammer Symmetrix is available for drilling 3" to 5-1/2" (76 to 139 mm) casings.
Micropiling - Using small diameter drilled casing pipes for various types of foundation work, king posts, or soldier piles. Also relatively large casings can now be drilled with smaller machines.
Suitable overburden system - Mainly non-retrievable Symmetrix, for non-retrievable piling casing pipes.
Foundation drilling - From small to large diameter drilled casings, for new foundation work or for renovation of buildings or bridge upgrading programs. This is typically done with large piling rigs or DTH-adapted cranes.
Suitable overburden system - Either retrievable or non-retrievable Symmetrix for piling casing pipes or even drill-through models for drilling rock sockets with a Symmetrix pilot bit.
Underpinning - An ingenious method of reinforcing existing foundations. Usually using small compact rigs with medium size drilled casings. Ideal in confined spaces such as tunnels, building and bridge renovations.
Suitable overburden system - Mainly non-retrievable Symmetrix for piling casing pipes or drill-through models for drilling rock sockets with a Symmetrix pilot bit.
Anchoring - A common method used for retainer wall construction, slope stabilization, seismic retrofitting, and building anchoring span stays. The most common equipment used for anchoring are geotechnical drill rigs with tophammer or DTH equipment.
Suitable overburden system - Retrievable Symmetrix with mainly retrievable threaded anchoring casing pipes.
Tunneling - In modern tunnel construction with unstable ground, a fan of grouted support casings (spiles) are drilled to form a protective arch prior to tunnel advancement. Symmetrix is also ideal for face stabilization such as drilling for dewatering and grouting holes for a TBM.
Suitable overburden system - Mainly tophammer Symmetrix models, for 3" to 4-1/2" (76 to 114 mm) tunneling casing pipes.
Marine works - Symmetrix is the most productive foundation method for marine applications. Ideal for piers, jetties, trestles, and underwater drilling and blasting. This is where Symmetrix-adapted cranes are ideal.
Suitable overburden system - Non-retrievable Symmetrix for integrated marine piling casing pipes.
Drill into bedrock then fill the casing with concrete and load-bearing elements (reinforcement bars).
Drill into bedrock, twist to unlock then continue drilling. Fill the casing with concrete and load-bearing elements (reinforcement bars).
Horizontal drilling - An efficient method for installing utility pipes under existing roads or buildings. Or for installing reinforced pipe roofs for underpasses. Especially useful in urban areas.
Suitable overburden system - Horizontal Symmetrix for breakthrough drilling and pipe roofing. Integrated Symmetrix versions for pipe roofing with blind end.
Special applications - Thanks to their versatility and flexibility, Symmetrix is now used in many niche applications. Secant pile walls, large diameter caissons, mechanically stabilized earth walls, and explosion compaction are just a few.
Suitable overburden system - The complete range of Symmetrix drill systems.
Special adaptations - This versatility has also lead to special adaptations of Symmetrix. For instance, we have developed a rotary drilling Symmetrix for simultaneous casing drilling. HDD applications can use adapted Symmetrix for quicker drilling and back reaming. Symmetrix can be adapted for drilling with plastic casing pipes.
Drilling with Rotary and DTH in the same hole
Due to Symmetrix's unique locking system it is possible to drill with a tricone bit or drag bit and with a DTH hammer in the same hole. A special ring adapter is used when drilling with the tricone or drag bit in order to rotate the ring bit. When DTH drilling is required, the drill string is lifted out and the DTH hammer with Symmetrix pilot bit is locked into the ring bit.
A system to cover your needs - Atlas Copco offers Symmetrix, an all-round overburden drilling system for holes of any depth or size.
Symmetrix - the all-rounder - Symmetrix is a concentric drilling system with retrievable pilot bits. They can be used for holes from 3" (76 mm) up to 48" (1220 mm). This system drills in any direction and in any type of ground condition. It is, in fact, the most flexible and efficient overburden system on the market today.
DTH or tophammer rigs - These two systems are so flexible that they can be used on DTH rigs or tophammer rigs. Even pile boring rigs, exploration rigs, or cranes can be adapted for use.
A multitude of applications - From anchoring to slope stabilization, from micropiling to curtain grouting, from tunnel forepoling to marine piling applications.
Wherever the ground is unstable, drilled casings offer the basis of an excellent solution.
The casing shoe is welded to the casing. The pilot bit and ring bit are locked together by the bayonet coupling.Together they drill a hole large enough to allow the casing to be pulled into the hole. The pilot bit and ring bit rotate with the drill string while the casing shoe and casing do not rotate.
