In geotechnical site investigations, knowing when to go beyond standard testing can make a critical difference in designing safe and efficient projects. This was the case during a recent field campaign by Pangea Geotecnia, where we encountered highly resistant ground that required us to extend our investigation beyond the conventional Standard Penetration Test (SPT).
What does the ground require?
Chile's geology is both complex and diverse. Across mining, infrastructure, and building projects, we frequently encounter dense, cemented, or highly variable soils where conventional investigation methods begin to reach their limits. While the SPT remains a fundamental tool in geotechnical engineering, it provides standard measurements that do not always represent the actual in situ ground conditions, particularly when soil resistance exceeds its typical operating range. no siempre reflejan la realidad del terreno in situ, especialmente cuando la resistencia del suelo sobrepasa sus rangos habituales.
The value of complementing the SPT with pressuremeter testing
During this field campaign, drilling began with dry sonic drilling, performed without the use of air or water, followed by the installation of casing to stabilize the borehole and prevent collapse. This step was essential for keeping the bottom of the borehole clean and providing suitable conditions for the subsequent testing.
Throughout the investigation, the groundwater level inside the casing was carefully maintained above the natural groundwater level. This precaution prevented phenomena such as piping, which could compromise the validity of the SPT results by introducing fines or water into the borehole.
Once the SPT had been completed, the recorded resistance exceeded 30 blows over the final 300 mm of penetration, indicating that additional testing was required to obtain a more representative characterization of the ground. Pressuremeter testing was therefore incorporated, with the test cavity prepared to allow accurate installation of the equipment.
What does the pressuremeter provide?
Unlike the SPT, the pressuremeter allows us to:
Measure the in situ strength and deformability of the ground directly.
Obtain representative data even in very dense soils.
Refine design parameters using measured ground conditions rather than estimated values.
This capability is particularly valuable in areas where ground conditions change rapidly with depth or where soils exhibit complex structures.
Investigating with precision means designing with confidence
At Pangea Geotecnia, we understand that every site has its own geological history, and that standard investigation methods do not always capture the complete picture. That is why we complement our investigation programs with techniques that allow us to go beyond conventional testing.
🎥 We invite you to watch the full field video, where we demonstrate the complete drilling, sampling, and pressuremeter testing process.