SPT (Standard Penetration Test)

What is the SPT?

The Standard Penetration Test (SPT) is a key geotechnical test used to characterize subsurface conditions before construction. Its main purpose is to provide reliable data on the soil’s bearing capacity, helping prevent differential settlement, foundation failures, and other structural risks.

If your project involves earthworks, foundations, or structural components, the SPT supports sound technical decisions from the outset, optimizing both safety and construction costs.

Test Procedure

Equipment: A steel rod with a split-spoon sampler is driven into the ground to retrieve a soil sample.
Execution: A 63.5 kg hammer is dropped from a height of 76 cm onto the sampling rod.
Measurement: The number of blows required to penetrate the soil in 15 cm intervals is recorded, until reaching the target depth or exceeding 50 blows, which indicates hammer rebound and high resistance.

SPT Applications

Determination of geotechnical parameters: Stratigraphy, shear strength, relative density, and bearing capacity.
Foundation design: Load-bearing calculations for various foundation types.
Geotechnical risk analysis: Evaluation of liquefaction potential and local stability during seismic events.

Advantages of the SPT

Efficiency and cost-effectiveness: A simple and economical method for obtaining geotechnical data.
Sample recovery: Allows for the collection of disturbed samples for laboratory analysis.
Broad applicability: Useful in both granular and cohesive soils, adaptable to various types of projects.

Important Considerations

Limitations in hard soils: In gravel or compacted soils, results may not reflect actual conditions without corrections.
Depth range: Most suitable for shallow to intermediate layers where detailed soil characterization is required.

Field Examples of the SPT Test

Below are real images of the Standard Penetration Test (SPT) being performed in the field. The photos show the drilling equipment, the split-spoon sampler, and the process of extracting disturbed soil samples at different depths. These samples are used to analyze key properties such as color, texture, and moisture—crucial information for soil characterization and informed construction decisions.

Disturbed soil samples extracted with the SPT

Visual analysis of soil samples obtained from SPT

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Processing, monitoring, and environmental consulting in hydrogeological studies, natural hazards, well drilling, water concessions, and Environmental Impact Assessments.