Detailed information on preparation of soil specimens for testing
(1) Detailed procedures are in the scope of CEN/TC 341, based on the test procedures, recommended by the European Technical Committee 5 on "Laboratory Testing" (ETC 5) of the International Society of Soil Mechanics and Geotechnical Engineering. The main requirements are given in this annex.
L.2 Preparation of disturbed soil for testing
L.2.1 Drying of soil
(1) Normally soil should not be dried before testing, unless otherwise specified, but should be used in its natural state. When drying of soil is necessary, one of the following methods should be used:
- oven drying to constant mass in ventilated oven at a temperature of (105 ± 5) °C;
- oven drying in ventilated oven at a specified temperature less than 100 °C (i.e. partial drying, since drying at a lower temperature needs not be complete);
- air drying (partial) by exposure to air at room temperature, with or without a fan.
(1) The extent of disaggregating to be applied, and the treatment of any remaining cemented material, should be related to the specific requirements and conditions, and should be specified. In particular, the disaggregating and the treatment should be done at the natural water content of the soil.
(2) Aggregations of particles should be broken down in such a way as to avoid crushing of individual particles. The action should be no more severe than that applied by a rubber-headed pestle. Special care is necessary when the soil particles are friable. If a large quantity of soil is to be prepared, disaggregating should be done in batches.
(1) Disaggregated soil should be mixed thoroughly before subdividing. The subdivision process should be repeated until representative samples of the specified minimum masses are obtained for use as test specimens.
L.2.4 Mass of disturbed soil for testing
(1) The minimum masses of disturbed soil required for testing are summarised in Table L.1. Where the minimum mass depends on the size of the largest particles present in significant quantity, this is related to the minimum mass required for sieving (denoted by "MMS") which is given in Table L.2.
(2) The required mass listed in Table L.1 allows for the preparation of one test specimen, with some allowance for wastage but not for the inclusion of over-size particles. When only the fine fraction of soil is required for testing, the prepared sample of the original soil should be large enough to provide the specified mass of the desired fraction.
(3) When it is necessary to remove large particles from the initial sample in order to prepare test specimens, the size range and the proportion by dry mass of the oversize material removed should be recorded.
|Test||Initial mass required||Minimum mass of prepared test specimen|
|Clay and silt||Sand||Gravelly soil|
|Water content||At least twice specimen mass||30 g||100 g||D = 2 mm – 10 mm
|D > 10 mm
0,3 × MMS,
min 500 g
|Particle density||100 g||10 g (particle size < 4 mm)|
|Sieving||2 × MMS||MMS|
|Hydrometer||250 g||50 g||100 g|
|Pipette||100 g||12 g||30 g|
|Consistency limits||500 g||300 g (particle size < 0,4 mm)|
|Density index||8 kg||a|
|"Proctor" mould||25 kg||10 kg|
|"CBR" mould||80 kg||50 kg|
|100 mm||4 kg|
|75 mm||3 kg|
|50 mm||500 g|
|38 mm||250 g|
|D Largest particle diameter in significant proportion (10% or more by dry mass)|
|MMS Minimum mass to be taken for sieving (see Table L.2)|
|NS Soil particles not susceptible to crushing|
|S Soil particles susceptible to crushing during compaction|
|a Muss of specimen depends on soil behaviour during test|
|b Permeability specimens with height equal to twice the diameter|
L.2.5 Preparation of soil for compaction
(1) Soil that is to be used for compaction-related tests should not be allowed to dry. If it is necessary to reduce the water content of the soil, this should be done by air drying.
(2) The upper limit of allowable particle sizes depends upon the size of the mould to be used. Particles larger than the sizes stated below should be removed before preparing the soil for testing (see Table L.3).
L.3 Preparation of undisturbed specimens
(1) The method of preparation of test specimens from undisturbed samples of soil depends on the type of sample and the type of specimen to be prepared.
(2) The approximate mass of soil required for typical laboratory test specimens is given in
Table L.4. The stated mass is sufficient for one test specimen with some allowance for wastage due to trimming.