Helical Auger boring and determination of water content and specific gravity

Theory:
Helical Augers are used to get the disturbed soil samples from the surface or near to the soil surface. The size of augers varies from 75mm to 200mm. These samples can be used to determine the nearest ground water level, or to determine the water content at various depths. Generally hand augers are used up to the depths of 6m but they can be used up to 30 m depths. Other properties such as particle size distribution and specific gravity can also be determined using these disturbed samples.

Hand Augers (Image source: www.bestengineeringprojects.com)

Apparatus/Equipment:

• Helical Auger bore with the handle
• Scale and sample collectors.
• Other apparatus for the water content determination and specific gravity determination, such as the oven, soil cans and pycnometer.

Procedure:

1. Fix the T-handle correctly to the Auger.
2. Press the auger into the ground and rotate the auger clockwise to get it sink into the ground to the required depth in the area under investigation.
3. When the annular space between the blades is filled with the soil, it is withdrawn and cleaned.
4. The cleaned auger is again inserted and the process is repeated.
5. Extension rods are attached when bore hole progresses downwards.
6. Take the samples from the various depths and then various tests are performed to check their properties.

Precautions:

1. The auger is rotated and pressed at uniform rate.
2. Clean the blades of the auger after the experiment is over.
3. Joining of the extension rods should be done carefully.
4. The sample should be collected at every 30cm boring and sample should be extracted whenever the strata is changed.
5. Straight driving should be done.

Limitations:

1. Helical Auger does not work in rocky strata.
2. Sample cannot be obtained under water.