Deep foundations

Ductile piles are made of ductile cast iron. In Slovenia they represent a new generation of foundations with driven piles. They were first used in Sweden and are very widely used in Finland, Germany and Austria. The system of piles consists of ductile pipes made using centrifugal casting with a patented component to join pipes.
Individual pipes are driven using high-frequency drivers, and connected without any special equipment to the desired lengths. Individual pipes are produced in lengths of 5 or 6 metres, but we can also order shorter pipes for work where space is limited. The pile material is cast iron (marked GGG – German Guss, Gray, Globular – casting, grey, graphite in the form of globules), which unlike grey cast casting does not corrode and is also resistant at high loads and burdens. Under deformation, ductile cast iron has ca 30% better properties than construction steel St.37. Installation of piles is fairly straightforward. At present, Vilkograd of Šentjur pri Celju has a machine fitted to drive piles.

Due to the low mass of piles (not more than ca 35 kg/m), piles are very easy to transport both to and within the construction site. We can also install them in compact and difficult places. Most of the time, no buffer layer or access ramp is required, thus minimizing the site preparation cost. We can also drive piles at various angles, including horizontally in special cases. The first pipe of the pilot is fitted with a shoe, installed at the final height of the excavation, and is then driven. We then connect the next pipe to it via a conical component.

Driving achieves a rigid and resistant connection. The pile is driven to the final depth with precisely measured energy, with any excess part of the pipe cut off at the planned height. The remainder of the pipe is then fitted with a drive shoe and then used for the next pile; they are thus also rational, as there is practically no waste. Piles may be filled with concrete. To increase bearing capacity, we can create an injected body by continually injecting around the pile. If we press concrete steel into a concrete mass that has not yet set, we can use such piles as tensile pilots or tensile geotechnical elements in general. The pile head is made depending on static needs. A load-distribution plate may be welded to the pile, since ductile cast iron may be welded with special electrodes.

So far we have given general descriptions of piles. As we recognize that project planning requires much more, we would also like to present the technical side. Technical data are based on actual measurements of individual projects. We have therefore – together with SLP, a company specializing in measurement of dynamic loads – demonstrated very surprising results in practical examples of projects.

A. Purpose and installation

• Piles are suitable for various foundations, including very large projects, rehabilitation of landslides, production of retaining walls, rehabilitation of foundations of existing structures etc.
• They are suitable in three different types of implementation with regard to the driving technique:
• Without injection,
• With subsequent injection and installation of reinforcement,
• With continuous injection, greatly increasing the surface area of the pile coating.
• Piles currently offered on the market are of diameter Ø 118 mm with wall thickness 8 -10 mm, and of diameter Ø 178 mm with wall thickness 8 – 13 mm.

After carrying out a number of driven pile projects, dynamic measurements were made of the load on piles. Pile measurements were carried out using the Pile Driving Analyser, Pak model. The method and procedure for measurement is standardised with the ASTM D4945-89 standard. After measurements are taken, data are analysed using the CAPWAP programme. In this way, we showed that Vilkograd’s pile driver can exceed the limit loads of piles. These loads range across the following values:

1. Vertical static bearing capacity for individual pile

1. Pilot of diameter f 118 mm uninjected, achieved bearing capacity from 400 to 550 kN
2. Pilot of diameter f 118 mm with subsequent injection, achieved bearing capacity 500 to 700 kN
3. Pilot of diameter f 178 mm uninjected, achieved bearing capacity 750 to 1050 kN
4. Pilot of diameter f 178 mm with subsequent injection, achieved bearing capacity 1100 to 1270 kN

The resistance of the soil, which varies from case to case, determines the bearing capacity of the pile.

2. Shear capacity

The limit shear capacity of ductile piles, assuming that shear capacity is equal to half of the tension at 0.2% plastic deformation, i.e. 150 Mpa, equals:

1. for piles of diameter f 118 mm, 220 kN
2. for piles of diameter f 178 mm, 380 kN

3. Conclusion

Based on all of this data, we conclude that the pile itself is very interesting technically and financially. It must be emphasised that Vilkograd has for the piles described above obtained recommendations regarding the technology and the use of driven piles made of ductile cast iron from the Institute of Geotechnics, Faculty of Civil Engineering, University of Maribor. These types of pile have many advantages, such as:

• resistance of material
• high corrosion resistance
• fast and quality implementation
• further work can begin immediately after implementation of piles, saving considerable time
• simple and safe use
• light weight
• relatively little construction equipment required
• small environmental impact
• surprising load results
• suitable for construction, civil engineering, supporting walls etc.
• production in very inaccessible terrains
• option of driving piles at an angle
• relatively large acceptable load
• 100% results pile binding
• no waste pipes in implementation
• low investment cost
• pile heads do not need special processing
• bearing capacity of piles can be determined on site by empirical calculation

Pile driving

Pile driving also possible at angles

Implementation of dynamic measurement using special method

Piles made

In this method, pipes are driven into soil. Piles are usually driven up to 1/3 into solid ground.

This implementation leads to bearing capacity values that depend on the bearing capacity of the ground.

pile 118 mm – 300 to 500 kN
pile 170 mm – 500 to 900 kN

This method is suitable for foundations where in the end we achieve a rigid base, rehabilitation of landslides, retaining walls, point foundations etc.

 

 

 

 

 

 

 

 

 

 

Pile driving with subsequent injection

In this method, we drive piles to the required depth, and then insert reinforcement and inject the pile with a concrete mix. This implementation achieves bearing values that depend on the bearing capacity of the ground.
pile subsequently injected fi 118 mm 350 to 600 kN
pile subsequently injected fi 170 mm 700 to 1050 kN

This method is mainly suitable for foundations where in the end we achieve a rigid base, rehabilitation of landslides, retaining walls, anchoring slopes, foundation beams etc.

 

 

 

 

Pile driving with continuous injectio

In this method, we drive piles with a base of greater diameter than the nominal diameter of the ductile pipe. At the same time as driving, we inject concrete under pressure, filling the bore. In this implementation, we can implement piles of diameter:

ductile pipe piles fi 118 mm from fi 150 mm to fi 200 mm

ductile pipe piles fi 170 mm from fi 200 mm to fi 300 mm

This implementation achieves bearing values that depend on the ground.

continuously injected pile fi 150 to fi 200 mm 300 to 600 kN
continuously injected pile fi 200 to fi 300 mm 700 to 110 kN

This method is mainly suitable when there is a requirement for the pile to bear on the coating, or when we do not achieve rigid terrain at depth. The pile in this case mainly bears loads on the coating.

 

 

 

 

 

 

Individual schematic cases of use of ductile piles

Foundation of bearers	Foundation of bearers	Foundation of shafts
Foundation of sewers	Retaining walls	Anchoring embankments
Foundation of silos	Dual foundation of structures	Classic foundation of structures
Anchoring slopes