🕑 Reading time: 1 minuteUncased cast in situ piles are used where the ground does not disturb the pile hole with soil or water falling in it. They are cheaper than the cased piles but not as much as efficient than cased piles. Skilled workers are required to install uncased cast in situ piles. The main disadvantage with these piles is no inspection is possible after the installation. The advantages are storage space is not required and special equipment is not needed.
Types of Uncased Cast-in-Situ Concrete PilesFollowing are the different types of uncased cast-in-situ concrete piles and their uses:
- Simplex pile
- Frankie pile
- Vibro pile
- Pedestal pile
Simplex PileSimplex pile is useful for both soft and hard soils. To obtain simplex pile, a steel tube with cast iron shoe is driven into the ground up to desired depth. After that, reinforcement is provided in the tube and then filled it with concrete. Then, the tube is slowly removed and cast-iron shoe is left at the bottom. So, for each pile new cast iron shoe should be attached. To overcome this, cast iron shoe with alligator jaw point is provided. Due to this jaw point, the shoe can be removed along with tube. The soil must be able to hold fresh concrete after removing tube.
FrankipileFrankie pile is suitable for granular type of soils and for soils bearing stratum of limited thickness is located at reasonable depth. This type of pile has mushroom shape bottom which acts like spread footing. To construct a Frankie pile, initially a pipe shell consisting concrete or gravel at bottom is placed on the ground with the help of leads. Next, a drop hammer of 20 to 30 kN weight is dropped using diesel machines on the concrete bottom. Then the whole arrangement is driven into the ground. After reaching hard strata, the concrete bottom expands and gains mushroom like shape due to hammer blows. After that, some proportion of concrete is placed in the tube and ramming is done with hammer. Similarly, ramming is done for every 300-mm layer up to the top. If reinforcement is to be provided, then the hammer goes inside the reinforcement cage. Frankie piles can carry up to 900kN.
Vibro PileVibro piles are suitable for soft soils which offers some amount of frictional resistance. Two different vibro piles are:
- Standard vibro pile
- Expanded vibro pile