The correct answer is D. All of the above.
Auger boring is a method of making a hole in the ground by rotating a hollow auger bit. The auger bit is typically made of steel and has a cutting edge on the end. As the auger bit is rotated, it cuts into the ground and removes the soil. The soil is then removed from the hole by a bucket or conveyor belt.
Auger boring is a relatively simple and inexpensive method of making a hole in the ground. It is often used for small-diameter holes, such as those used for installing fence posts or utility lines. Auger boring can also be used for larger-diameter holes, such as those used for installing water wells or septic systems.
Auger boring is generally employed in cohesive and other self soils above water table. Cohesive soils are soils that have a high clay content. They are relatively strong and can hold their shape without collapsing. Other self soils are soils that are not cohesive, but that are still strong enough to hold their shape without collapsing. These soils include sand and gravel.
Auger boring is most economical up-to a depth of 5 meters. This is because the cost of auger boring increases with the depth of the hole. For holes that are deeper than 5 meters, other methods of excavation, such as drilling or blasting, may be more economical.
In conclusion, auger boring is a simple, inexpensive, and effective method of making a hole in the ground. It is generally employed in cohesive and other self soils above water table and is most economical up-to a depth of 5 meters.