2.4.3 Ground properties
(1)P Properties of soil and rock masses, as quantified for design calculations by geotechnical parameters, shall be obtained from test results, either directly or through correlation, theory or empiricism, and from other relevant data.
(2)P Values obtained from test results and other data shall be interpreted appropriately for the limit state considered.
(3)P Account shall be taken of the possible differences between the ground properties and geotechnical parameters obtained from test results and those governing the behaviour of the geotechnical structure.
(4) The differences to which 2.4.3 (3)P refers can be due to the following factors:
- many geotechnical parameters are not true constants but depend on stress level and mode of deformation;
- soil and rock structure (e.g. fissures, laminations, or large particles) that may play a different role in the test and in the geotechnical structure;
- time effects;
- the softening effect of percolating water on soil or rock strength;
- the softening effect of dynamic actions;
- the brittleness or ductility of the soil and rock tested;
- the method of installation of the geotechnical structure;
- the influence of workmanship on artificially placed or improved ground;
- the effect of construction activities on the properties of the ground.
(5) When establishing values of geotechnical parameters, the following should be considered:
- published and well recognised information relevant to the use of each type of test in the appropriate ground conditions;
- the value of each geotechnical parameter compared with relevant published data and local and general experience;
- the variation of the geotechnical parameters that are relevant to the design;
- the results of any large scale field trials and measurements from neighbouring constructions;
- any correlations between the results from more than one type of test;
- any significant deterioration in ground material properties that may occur during the lifetime of the structure.
(6)P Calibration factors shall be applied where necessary to convert laboratory or field test results according to EN 1997-2 into values that represent the behaviour of the soil and rock in the ground, for the actual limit state, or to take account of correlations used to obtain derived values from the test results.
2.4.4 Geometrical data
(1)P The level and slope of the ground surface, water levels, levels of interfaces between strata, excavation levels and the dimensions of the geotechnical structure shall be treated as geometrical data.