Principle and application
The continuous soil sampler works inside the hollow-stem auger string and recovers the soil profile in 101.6 mm (4") plastic tubes up to 1.40 m long, dry, while drilling advances. A core barrel with a plastic liner sits inside the lead auger, with its mouth at the excavation face: while the auger teeth cut the outer ring of soil, the central core remains intact and enters the tube as the string advances.
The sampler is stationary: rigid hex rods support it inside the string and a locking plate fixed to the mast prevents the inner assembly from rotating. Rotation stays with the auger alone, and this decoupling is what preserves the sample structure. Sampling happens together with drilling, with no dedicated recovery runs and no water.
The operating cycle
Positioning
The sampler with a plastic liner is lowered on the hex rods and seats inside the lead auger of the string.
1.40 m advance
The auger rotates and advances; the central core enters the tube, which does not rotate. No water, no remoulding.
Retrieval
The rigid rods hoist the sampler. The auger string stays in the hole, casing the walls.
Sealed liner
At the surface, the liner with the sample is capped at both ends, labelled and goes intact to logging and testing.
New cycle
An auger is added to the string, a new liner goes down and the advance continues: a profile with no gaps.
As continuous sampling
| Sample | Continuous, 101.6 mm (4") in diameter, up to 1.40 m per run |
|---|---|
| Drilling | Dry, with no water or circulation fluid; the auger itself cases the hole |
| Sampler | Stationary, locked to the mast: it does not rotate with the auger string |
| References | ASTM D6151 (hollow-stem auger) · quality criteria of ISO-22.475-1 |
Quality and field operation
Data quality
- Shoe adjustable in 2.5 cm increments: advanced in soft soils, retracted in hard materials.
- Retrieval on rigid rods, with no cable: exact depth and no risk of losing the sample in the hole.
- No drilling fluid: no washing and no cross-contamination.
- Immediate liner sealing and traceability by borehole and depth.
Site standard
- Qualified for high-compliance areas: mining, industry and ports.
- Organised, signed work front with an HSE procedure in place.
- Own crews and fleet, including night shifts.
The deliverable
| Continuous profile | Liners sealed and labelled by borehole and depth, with no gaps along the hole |
|---|---|
| Record | Log with depth, recovery and tactile-visual description of the layers |
| Forwarding | Straight to the soil laboratory, when integrated |
| Typical lead time | According to the field campaign |
Sectors and project types
Frequently asked questions about continuous sampling
What is the continuous soil sampler?
It is a sampling system that works inside the hollow-stem auger string and recovers the soil profile in 101.6 mm plastic liners every 1.40 m of advance, dry. The sampler is stationary: the auger rotates around it, and the sample reaches the surface intact and well preserved.
What is the advantage over SPT sampling?
The SPT samples the soil at 1 metre intervals; between them, thin layers and transitions can go unnoticed. Continuous sampling recovers the whole profile, with no gaps, allowing detailed description of layers, transitions and structures, with less field time per sampled metre.
Is the sample undisturbed?
Since the tube does not rotate with the auger and drilling needs no fluid, the sample preserves structure, natural moisture and stratification. In cohesive soils it can meet the quality criteria of ISO-22.475-1. Where the project requires dedicated undisturbed samples, continuous sampling is combined with Shelby or Denison in the same borehole: continuous description plus premium sampling points.
Does it work for compacted fill control?
Yes. Continuous recovery in tubes allows the degree of compaction to be determined in deep fill layers, a long-standing use of this sampler at Damasco Penna.
Continuous soil sampler in a hollow-stem auger
Technical Bulletin No. 04: operating principle, operating cycle, shoe adjustment and sample quality criteria.
Continuous sampling for your project
Tell us about your project and we will prepare the investigation plan and the quote.