Sample quality class
Soil samples used for laboratory testing are classified in five Quality Classes with respect to the soil characteristics that remain unchanged during sampling or handling. In the following table the characteristics of every class can be found.
Description classes
| Class | Description class |
|---|---|
| QM1 | Layering, internal layering, consistency, field humidity and tension status are all intact and unchanged |
| QM2 | Layering, internal layering, consistency, field humidity are all intact and unchanged |
| QM3 | Layering, internal layering, field humidity are all intact and unchanged |
| QM4 | Layering is intact and unchanged |
| QM5 | Layering is not intact and changed |
Sample quality classes by the BRO
Ideally, one would always want to examine the subsurface in-situ, but in practice, one examines samples from the subsurface and that means that there is inevitably some degree of disturbance. The degree of disturbance is primarily determined by the choice of drilling technique, sampling method and sampling device. Because the composition of the soil is also of influence, it may be necessary to adjust the choice if the type of soil turns out to be different from what was assumed. The sampling quality indicates within which limits the primary degree of disturbance lies. In the NEN-EN-ISO 22475 a classification into five classes is given and for each class it is determined how the samples must be treated once they have come above the ground. The lowest requirements apply to samples whose cohesion is already completely disturbed when they come above ground. In everyday speech, those samples are called stirred samples. The four other classes describe the requirements for handling of undisturbed samples. The reason to record the data is that not all samples taken in the field are always analyzed as a part of the drilling study. The classes are described below.
Class A
Sampling is aimed at obtaining undisturbed samples and avoiding irreversible changes in the stress state. Immediately after sampling, the samples are packed airtight to prevent oxidation as much as possible. In this class the samples are stored and transported in sealed sample containers of sufficient strength to prevent damage and moisture loss. When the samples are stored on site, during transport and in the laboratory the temperature needs to be between 8 and 12 degrees Celcius and the humidity needs to be at least 90%. The sample containers are also protected from vibration and shocks during transport.
Class B
Sampling is aimed at obtaining undisturbed samples where changes in the stress state are tolerated. Immediately after sampling, the samples are packaged airtight to prevent oxidation as much as possible. The samples are stored and transported in sealed sample containers of sufficient strength to prevent damage and moisture loss. The sample containers are protected from vibration, shocks and extreme temperature.
Class C
Sampling is aimed at obtaining samples where the stratification and the internal structure are preserved. Immediately after sampling, the samples are packaged airtight to prevent oxidation as much as possible. The samples are stored and transported in sealed sample containers of sufficient strength to prevent damage and moisture loss.
Class D
Sampling is aimed at obtaining samples where stratification is preserved. Immediately after sampling, the samples are packaged airtight to prevent oxidation as much as possible. The samples can be collected and stored in PVC or metal sample containers.
Class E
Sampling is aimed at getting a good impression of the composition of the subsoil. No special requirements apply. The samples can be collected and stored in sample containers, bags, jars, etc.
References
- NEN-EN-ISO 14688-1:2019
- BRO-Catalogus Geologisch booronderzoek versie 0.99