Drilled pier foundations are in the same category as pile foundations. No sharp divergence can be made between piers and piles as they both serve the same purpose. The distinctions are based on the method of installation. Pile is done by driving, whereas by digging, the pier is laid. Thus, a foundation unit installed in a drill hole may also be called a rugged cast-in-situ concrete pile. Here, a distinction is made between a small diameter pile and a large diameter pile. Pile, cast-in-situ, less than 0.75 m (or 2.5 ft) in diameter is sometimes called small diameter pile. A pile larger than the above size is called bore-cast-in-situ pile of larger diameter. The latter definition is used in most non-US countries while in the United States, rugged piles of such large diameters are called drilled piers, drilled shafts, and sometimes drilled caissons.,
Different types of drilled piers
Drilled piers can be described under four types. All four types are similar in construction technology, but differ in their design assumptions and the mechanism of load transfer to the surrounding Earth mass. These types are shown below.
1. straight-shaft end-bearing piers
straight-shaft end-bearing piers Develop your support from end-bearing on strong soil, “hardpan” or rock. It is assumed that the soil above contributes nothing to support the load applied to the pier (Figure-1).
2. straight-shaft side wall friction piers
straight-shaft side wall friction piers Overburden passes through soils that are assumed to carry no load, and the wall friction between the mooring and the bearing layer (Fig. 2) is sufficient to develop the designed load capacity at a specified bearing level. penetrates far.
3. Combination of straight shaft side wall friction and end bearing piers
Combination of straight shaft side wall friction and end bearing piers The two mentioned above are of similar construction, but with wall friction on either side and end bearing assigned a role in carrying the design load. When carried into the rock, this pier may be referred to as a socketed pier or a “drilled pier with rock socket” (Figure-3).
4. Belted or Under Remade Pierce
Belted or Under Remade Pierce Below the bell or ream are the ghats below (Fig. 4). A large percentage of the load applied to the top of the pier is believed to be borne by the base.