Undisturbed sampling with Geofrost Coring

The method provides undisturbed cores from all kinds of ground conditions, also rock fissure fillings, coarse or loose frictional materials, talus, moraine with rock, fill material and other different mixed ground conditions. Standard diameter is 105 mm. Samples may be tested in frozen or unfrozen conditions.

Undisturbed soil samples by GEOFROST Coring.
Photo: Geofrost

Before GEOFROST Coring

GEOFROST Coring - undisturbed sample of talus with rock pieces, gravel, sand, silt, clay, frozen water, and empty voids.
Undisturbed sample of moraine taken up from the ground.
Photo: Geofrost
Earlier, infrastructure projects and complex civil works often had to live with a high degree of uncertainty because it has been very difficult, or impossible, to obtain material for testing for a broad range of ground conditions. Not anymore.

Such difficult ground conditions are rock fissure fillings, coarse or loose frictional materials, talus, moraine with rock, fill material and other different mixed ground conditions. The uncertainties remains through all the phases of the project and may be critical due to choice of location, alignement, method, design and execution. The uncertanties often result in unforeseen ground conditions, which often are the reason to financial budget overruns and legal disputes.

Undisturbed samples

GEOFROST Coring - undisturbed sample of talus with rock pieces, gravel, sand, silt, clay, frozen water, and empty voids.
GEOFROST Coring - undisturbed sample of talus with rock pieces, gravel, sand, silt, clay, frozen water, and empty voids.
Photo: Geofrost
Conventional soil sampling may only retrieve undisturbed samples from clay. Many ground conditions make sampling difficult and typical problems are washout of rock fissure fillings, broken structure of frictional material, washout of fines, washout or relocation of liquid contamination and often core loss.

Geofrost Coring is fundamentally different. The properties of the ground are encapsulated, resulting in samples with preserved fissure filllings, fines, grain structure, contamination in rock fissures, fines in mixed ground, contamination in original location and even open voids. The encapsulation made by freezing protects the sample from disturbance during sampling, transportation and handling.

Lab

All standard tests like soil classification, strength and deformation properties, hydraulic and thermal properties, are performed in the laboratory. Correct parameters are determined because the sample is encapsulated all the way from retrieval from the ground to being incorporated in the test apparatus.

Conditions from the in situ situation, like consolidation and water pressure, are recreated in the test apparatus, assuring that the test results in correct strength and deformation properties. Grain size distribution, water content and permeability are preserved from sampling, completely unaffected by the sampling procedure.

Laboratory testing
Laboratory testing
Photo: Geofrost

Frozen properties

The cores may be tested in frozen condition to find the frozen strength and deformation properties, as well as thermal properties. These properties are used when designing Geofrost structures and in permafrost engineering. The cores are prepared in frozen condition also for tests in unfrozen state in order to best preserve the in situ properties.

Documentation

We deliver complete geotechnical investigation reports with photo documentation, classification and results from standard tests and special tests, from both frozen and unfrozen material, depending on requirements. Continuous sampling in desired depth intervals to be investigated may be performed.

Beneficial decision basis

Accurate and reliable in situ properties contribute to high quality information and a good basis for making correct decisions in the project, removing uncertainty and reducing risks and costs.

Clients