Solid Stem
Augering and Hollow Stem Augering

What It Is:

Solid stem augering uses a continuous flight auger with a solid center shaft. The auger cuts through soil and lifts cuttings to the surface via helical flights.

How It Works:

• The solid stem auger is rotated into the ground.
• The flights convey soil to the surface as the auger advances.
• No access through the auger shaft—sampling or instrumentation must occur after the auger is withdrawn.

Characteristics:

• Borehole is unsupported once the auger is removed.
• Can collapse in loose or saturated soils if not cased immediately.
• Suitable for cohesive or stable soils (e.g., clays, silts).

Pros:

• Simple and cost-effective
• Fast in stable ground
• Good for general soil profiling

Cons:

• Cannot be used for in-situ sampling or groundwater installation while auger is in place
• Not ideal in loose, granular, or saturated soils

Common Uses:

• Shallow soil borings
• Site classification
• Simple geotechnical logs

Hollow Stem Augering

What It Is:

Hollow stem augering uses a continuous flight auger with a hollow center shaft and a removable plug or pilot bit at the bottom. This system allows access to the borehole without removing the auger.

How It Works:

1. Auger with a plugged center is advanced to target depth.
2. The plug or bit is removed, creating open access down the hollow center.
3. Sampling tools, piezometers, or monitoring wells are inserted through the hollow stem.
4. Once complete, the auger is withdrawn, leaving instrumentation in place if desired.

Characteristics:

• The auger acts as temporary casing, supporting the borehole wall.
• Maintains hole integrity in loose or saturated soils.

Pros:

• Allows sampling or installation without pulling the auger
• Ideal for monitoring well or piezometer installation
• Safer in unconsolidated soils or groundwater conditions

Cons:

• More complex and costly than solid stem
• Requires larger rig and more maintenance

Common Uses:

• Environmental site assessments (ESA)
• Monitoring well installation
• Geotechnical investigations in unstable soils

Summary

• Use Solid Stem Augering for simple, shallow borings in firm soils where borehole collapse is not a risk.
• Use Hollow Stem Augering when you need well installations, in-situ sampling, or are working in unconsolidated or groundwater-bearing zones.