What is Auger Boring and how Borehole is made using hand auger?
Operations like boring doesn’t allow direct access to the subsoil and holes are bored into the ground by hand or power arguers and etc. Practically, auger boring is a device or an instrument as we say in general language which supports us in developing a borehole into the ground.
In the market, different power operated and hand operated augers can be found. Among them, two types of hand operated augers; post-hole type and helical type have been clearly shown in the figure. Among these two, post-hole type augers are common in use. As clearly seen from the figure, the bottom part is pressed into the ground and handles provided at the top are used to rotate the augers.
During the continuous process of pressing and simultaneous rotation, the auger is gently driven into the ground. After sometime when auger reaches a finite depth and is completely filled with soil, it is taken out on the ground surface and the soil is removed from the auger.
The depth of holes made by hand operated augers is about 30 m. The use of augers in boring is suitable for all types of soil except gravels and boulders. To add more, auger boring is the cheapest way to advance a borehole into the ground. Other type of auger; hollow stem auger is that type of device which acts as its own casing. It can bore a hole rapidly up to a depth of 60 m.
If holes are to be advanced below water level in sandy strata, boreholes should be cased. In general cases, we prefer auger boring where the sides of borehole can stand without external supports. Samples thus obtained are disturbed but representative. Generally, auger boring is used in fields where it is not necessary to bore a hole more deep than 6 m. This method is extensively used in soil investigation works for railroad, highway or airport construction where depth of borehole is usually less than 6 m.
In case of situations when deeper holes are to be bored into the ground, power augers are used. The diameter of augers used varies from 75 mm to 300 mm and they are often used in cohesive soils. For large augers, trucks mounted auger type drilling machine are used to construct large shafts of several mm diameter. But, this method is much expensive and not reasonable unless the project is very large and vital.