Classification testing of rock material
(1) The classification of the rock mass based on cores calls for the highest possible core recovery to identify discontinuities and possible cavities. The disturbance of the core from the drilling process should be minimised since most rock quality designations relate to the fractures found in the cores.
(2) Most classification systems relate to cores and rotary drilling samples with a sample diameter of at least 50 mm. For most tests, a non-fractured core length of 50 mm to 200 mm long is sufficient for element testing.
NOTE 1 Examples of tests for the classification of rock arc given in the documents listed in X.4.9.
NOTE 2 Nationally and internationally recognised classification systems exist for different purposes. Rock mass classification systems, based on semi-numerical methods, exist for engineering purposes as summarised by Bieniawski (1989) Engineering Rock Mass Classification, (see X.5).
U.2 Rock identification and description
(1) EN ISO 14689-1 applies to the description of rock for geotechnics in civil engineering. The description is carried out on cores and other samples of natural rock and on rock masses.
(2) Any published and locally approved classification system may be used, provided the report gives a traceable reference.
NOTE Examples of additional description procedures are given in the documents listed in X.4.9.1.
U.3 Water content
U.3.1 Test procedures
(1) If specified, accuracy checks should be carried out by comparing results on specimens taken in parallel within the same formation.
NOTE Examples of test procedures are given in the documents listed in X.4.9.2.
U.3.2 Number of tests
(1) In general, the water content should be taken at least one per metre of core.
U.4 Density and porosity
U.4.1 Test procedures
(1) The determination of the porosity (or void ratio) calls for a determination of the density of solid particles (or an estimate of it based on local experience with similar rock type).
(2) The existence of closed pores may influence the porosity. Determination of the total pore volume may be based on the density of solids of a powdered sample, however the determination of the amount of open and closed pores calls for specialised analysis.
(3) Methods using mercury displacement should be avoided.
NOTE Examples of test procedure are given in the documents listed in X.4.9.3.
U.4.2 Number of tests
(1) The density and porosity should be determined once at least every two metres, and at least once for each differentiated rock type unit, regardless of the rock homogeneity. The density/porosity parameters represent part of the framework for most evaluations of rock strength and deformation properties.
Swelling testing of rock material
(1) Undisturbed rock specimens should preferably be tested where possible, since rock fabric has an important effect on swelling characteristics. Where the sample is too weak or too broken to allow preparation, such as joint fill material, the swelling index tests may be carried out on remoulded and re-compacted specimens. The procedures used should then be described in the report.
(2) Table V.1 gives a guideline for the minimum number of swelling tests required for different specimen dimensions. The suggestions apply for sites with a limited risk of occurrence of swelling rock types. For sites with rock types more likely to be subject to swelling, the number of tests should be increased to at least the double of the numbers given in the table. Other advanced tests may be better suited to determine the in-situ swelling performance.
NOTE Examples of tests for swelling of rocks are given in the documents listed in X.4.10.
|Test type||Minimum thickness||Minimum diameter||Minimum number of test specimens||Notes|
Swelling pressure index under zero volume change
|15 mm and/or 10 times max particle size||2,5 times thickness||3||Specimen should fit closely in the ring|
Swelling strain index for radially confined specimen with axial surcharge
|15 mm and/or 10 times max particle size||4 times thickness||3 + duplicate specimens for water content||Specimen should fit closely in the ring|
Swelling strain developed in unconfined rock specimen
|15 mm and/or 10 times max particle size||15 mm and/or 10 times max particle size||3 + duplicate specimens for water content||—|
V.2 Swelling pressure index under zero volume change
(1) The testing apparatus may often be an ordinary oedometer cell for soil consolidation. However, the apparatus should be very stiff in order to avoid influence of deformations of the cell itself.
NOTE An example of a test for the swelling pressure index under zero volume change is given in the document listed in X.4.10.1.
V.3 Swelling strain index for radially-confined specimen with axial surcharge
(1) The example specifies a loading device capable of applying a sustained pressure of 5 kPa to the specimen under water flooding. However, more appropriate to represent the field, may be specified. The report and any evaluation should include description of any such procedural deviations.
NOTE An example of test for swelling strain developed in an unconfined rock specimen is given in the document listed in X.4.10.2.
V.4 Swelling strain developed in unconfined rock specimen
NOTE An example of tests for swelling strain developed in an unconfined rock specimen is given in the document listed in X.4.10.3.