Cased piles consist a shell around it and these piles when casted in site are called cased cast-in-situ concrete piles. Types and advantages of these piles are discussed.
In case of cased cast in situ piles, the shell is usually made of steel. This type of piles is suitable for any types of soils.
Advantages of Cased Cast-in-Situ Concrete Piles
Main advantages of cased cast in situ piles are as follows.
- The shell has driving resistance so, it can be easily driven.
- Concrete filling is not disturbed.
- Internal inspection can be done after driving shell.
- Piles can be easily cut or extended in case of cased piles.
Types of Cased Cast-in-Situ Concrete Piles and Uses
Different types of cased cast in situ concrete piles are:
- Raymond piles
- Mac-Arthur piles
- Union metal monotube pile
- Swage pile
- Western button bottom pile
Raymond piles are economical piles of cast in situ piles which are developed by A.A. Raymond in 1897. There are two types of Raymond piles are available, namely
- Standard Raymond pile
- Step taper Raymond pile
Standard Raymond Pile
Standard Raymond pile is used as friction pile because of its heavy taper of 1 in 30. Diameter of Raymond pile gradually decreases from top to bottom. At the top 40 to 60 cm and at the bottom it varies from 20 to 30 cm. The length of Raymond piles varies between 6 to 12 meters.
The Raymond pile contains corrugated steel shell which is closed at the bottom and is reinforced with wire. Wire is wounded spirally around the shell with 8 cm pitch.
The shell is driven into the ground by placing core or mandrel in it. After reaching required depth, mandrel part is removed and is filled with concrete.
Step Taper Raymond Pile
In this case of step taper Raymond pile, the pile consists series of shells, which are placed one above the other. But each shell is of different size, i.e. shell size is gradually increased from bottom to top.
To ease driving, bottom shell should be made of heavier gauge and closed at bottom. Then next shell section is placed on it. The connection between steel shells are done by the screw connections.
Usually 2.5 cm increase in diameter is provided for shells with respect to their bottom one. Also, steel mandrel or core is used to driven the shell sections. Step taper random piles can be driven up to 36 m of depth.
This type of pile can be useful as friction pile as well as end bearing pile. The advantage compared to standard random pile is that it can be inspected easily, fresh concrete can be filled and length flexibility.
Mac Arthur Piles
Mac Arthur piles generally in uniform diameter and shell is made of corrugated steel. But driving is done by the combination of steel casing of heavy gauge consisting core.
After driven to require depth, the core is removed and corrugated steel shell is inserted in heavy gauge steel casing. Then, concrete is filled in the corrugated steel shell and outer hard casing is removed.
Union Metal Monotube Pile
Union metal monotube piles consists only shell without any mandrel. The shell is made of steel and is tapered fluted.
These types of piles are well suitable for most of the soil conditions that is from end bearing to friction load carrying soils.
The shell is more rigid and watertight and this shell can be driven to larger depth using hammer. After driving, inspection is done and then concrete is filled in the shell.
Swage piles are widely used in case of hard soils. Pre-cast concrete plug is attached at bottom of shell to drive the pile shell. Steel core is inserted in shell and driven and then shell is swaged out by the taper of the plug and form water tight joint.
Next the whole arrangement is driven into the ground to a required depth. After reaching desired depth, core is taken out and the pipe or shell is filled with concrete.
Western Button Bottom Pile
Western button bottom piles are widely used in end bearing soils. The pile consists a concrete button at the bottom which helps the pile to drive into ground.
This concrete button is wider (about 25 mm diameter) and sharp at bottom so, it makes wider hole and eliminates side friction.
Initially the steel pipe with 12mm thick wall is placed on concrete button and this combination is driven into the ground. After reaching desirable depth, corrugated steel shell is placed in the steel pipe. This shell consists steel plate welded at bottom and this plate is attached to concrete button using long socket wrench.
Finally, the casing is removed and concrete is filled in the shell. This type of piles can be used up to 23m and for loads up to 50 tons.