Cast-in-situ Piles: Advantages and Disadvantages.

Cast-in-situ piles are concrete piles. These piles are distinguished from drilled piers as small
diameter piles. They are constructed by making holes in the ground to the required depth and then
filling the hole with concrete. Straight bored piles or piles with one or more bulbs at intervals may
be cast at the site. The latter type are called under-reamed piles. Reinforcement may be used as per
the requirements. Cast-in-situ piles have advantages as well as disadvantages.

Advantages
1. Piles of any size and length may be constructed at the site.
2. Damage due to driving and handling that is common in precast piles is eliminated in this case.
3. These piles are ideally suited in places where vibrations of any type are required to be avoided to preserve the safety of the adjoining structure.
4. They are suitable in soils of poor drainage qualities since cast-in-situ piles do not significantly disturb the surrounding soil.

Disadvantages
1. Installation of cast-in-situ piles requires careful supervision and quality control of all the materials used in the construction.
2. The method is quite cumbersome. It needs sufficient storage space for all the materials used in the construction.
3. The advantage of increased bearing capacity due to compaction in granular soil that could be obtained by a driven pile is not produced by a cast-in-situ pile.
4. Construction of piles in holes where there is heavy current of ground water flow or artesian pressure is very difficult.

A straight bored pile is shown in Fig. 15.1 (a).

Figure 15.1 (a) cast-in-situ.