Geotechnical Drilling & Soil Investigation
Before any foundation, retaining structure or infrastructure project, you need to know what lies beneath the ground. Geotechnical drilling opens boreholes in the terrain, collects soil and rock samples, measures the water table position and determines the strength of the ground — the foundation on which the structural design is safely sized.
What we deliver
Six lines of subsurface investigation, combined according to the ground conditions found in the field.
- Rotary and mixed drilling
- SPT and SPTT percussion drilling, and auger drilling
- Shelby, Denison and undisturbed block sampling
- Piezometer installation
- Soil permeability testing
- Pressurized water-loss testing
How we do it
The investigation combines rotary and mixed drilling with percussion drilling (SPT and SPTT) and auger advance, depending on the formation encountered. The SPT drives a split-barrel sampler into the bottom of the borehole with a standardized 63.5 kg hammer falling from 75-76 cm, counting the blows required for each 15 cm of penetration; the N value — the sum of blows from the 2nd and 3rd 15 cm intervals, totaling 30 cm — is the most widely used empirical index in the world for estimating relative density in sands and consistency in clays. Undisturbed samples are collected with thin-walled tubes (Shelby), fixed-piston samplers (Denison) and undisturbed blocks, preserving the soil structure for laboratory strength and consolidation testing. Piezometers installed in the boreholes monitor the position and variation of the water table over time. Soil permeability tests and pressurized water-loss tests in rock mass complete the hydraulic characterization of the ground.
Measured parameters
The SPT N value is the most widely used empirical index in the world for estimating relative density in sands and consistency in clays — corrected to 60% of the system's theoretical energy (N60) when the project requires comparison between equipment.
| Item | Valor | Unidade |
|---|---|---|
| N value (N-SPT) | N | blows / 30 cm |
| N corrected to 60% of the system's theoretical energy | N60 | blows / 30 cm |
Applicable standards
The SPT follows international standards that standardize equipment, procedure and refusal criteria — making results comparable across campaigns and countries.
| Item | Valor |
|---|---|
| Standard Test Method for Standard Penetration Test (SPT) and Split-Barrel Sampling of Soils | ASTM D1586 / D1586M-18(2018) |
| Geotechnical investigation and testing — Field testing — Standard penetration test | ISO 22476-3 |
| Manual on Subsurface Investigations | FHWA NHI-01-031 |
| Geotechnical Investigations | USACE EM 1110-1-1804 |
Honest limitations
We publish where the method reaches its limits — mastering a technique also means knowing where it stops.
- The sample obtained in the SPT is disturbed, unsuitable for structure, in-situ density or consolidation testing.
- The test has low repeatability: it is sensitive to borehole cleaning, hammer type and operator experience, with energy efficiency ranging from 45% to 83% depending on the equipment.
- In very soft or very loose soils, the driving itself can disturb or liquefy the tested material, reducing the reliability of the result.
- Empirical correlations between the N value and engineering parameters have variable quality — none is of high absolute precision.
Need a reliable geotechnical investigation?
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