Under-reamed piling pipe have mechanically formed enlarged bases that are as much as 6 m in diameter.The form is that of an inverted cone and can only be formed in stable soils. The larger base diameter allows greater bearing capacity than a straight-shaft pile.
These piling pipe are suited for expansive soils which are often subjected to seasonal moisture variations, as also filled up ground and loose or soft strata. They are used in normal ground condition also where economics are favorable.
Augercast piling
An augercast pile, often known as a continuous flight augering (CFA) pile, is formed by drilling into the ground with a hollow stemmed continuous flight auger to the required depth or degree of resistance. No casing is required. A cement grout mix is then pumped down the stem of the auger. While the cement grout is pumped, the auger is slowly withdrawn, conveying the soil upward along the flights. A shaft of fluid cement grout is formed to ground level. Reinforcement can be installed. Recent innovations in addition to stringent quality control allows reinforcing cages to be placed up to the full length of a pile when required. A typical reinforcing cage will consist of 4 to 8 bars from #5 to #8 bars typically 1/3 the length of the pile with longitudinal circular ties spaced along the length of the cage. Where tension loads are present it is typical to see a single full length bar placed at the center of each pile.
Pier and grade beam foundation
In drilled pier foundations, the piers can be connected with grade beams on which the structure sits, sometimes with heavy column loads bearing directly on the piers. In some residential construction, the piers are extended above the ground level and wood beams bearing on the piers are used to support the structure. This type of foundation results in a crawl space underneath the building in which wiring and duct work can be laid during construction or re-modelling.
