1.6 Test results and derived values
(1) Test results and derived values form the basis for the selection of characteristic values of ground properties to be used for the design of geotechnical structures, in accordance with 2.4.3 of EN 19971:2004.
NOTE 1 The process of geotechnical design consists of a few successive phases (see Figure 1.1), the first of which covers the site investigation and testing, whereas the next one is devoted to the determination of characteristic values, and the last phase covers the design verification calculations. Rules for the first phase are given in the present standard. The determination of characteristic values and the design of the structures are covered by EN 19971.
Figure 1.1 — General framework for the selection of derived values of geotechnical properties
(2) Test results can be experimental curves or values of geotechnical parameters. In Annex A, a list of test results is given to serve as a reference to test standards^{7}.
^{7} Geotechnical test standards, yielding these results are prepared by CEN/TC341.
(3) Derived values of geotechnical parameters and/or coefficients, are obtained from test results by theory, correlation or empiricism.
NOTE 2 The examples of correlations used to determine derived values given in the annexes to Section 4 of this standard arc obtained from the literature. These correlations may correlate the value of a geotechnical parameter or coefficient with a test result, such as the q_{c}value of a CPT. They may also connect a geotechnical parameter to a test result by means of theoretical considerations (for example, when deriving a value of the angle of shearing resistance φ' from pressuremeter lest results or from the index of plasticity).
NOTE 3 In certain cases, the derivation of geotechnical parameters by means of a correlation is not made before the determination of the characteristic value, but after the test results have been corrected or transformed into conservative estimates.
1.7 The link between EN 19971 and EN 19972
(1) Figure 1.2 presents the general architecture of the CEN standards related to geotechnical engineering problems and those directly linked to EN 1997. The design part is covered by EN 19971. The present standard gives rules for ground investigations and obtaining geotechnical parameters or coefficients values to be used for determining the characteristic values (as specified in EN 19971). It gives also informative examples of calculation methods for spread and deep foundations. The implementation of EN 1997 needs information based on other standards, in particular those related to ground investigations and to the execution of geotechnical works.
EN 19971
Design rules
 General framework for geotechnical design
 Definition of ground parameters
 Characteristic and design values
 General rules for site investigation
 Rules for the design of main types of geotechnical structures
 Some assumptions on execution procedures

EN 19972
Geotechnical investigation and testing
 Detailed rules for site investigations
 Genera] test specifications
 Derivation of ground properties and geotechnical model of the site
 Examples of calculation methods based on field and laboratory tests

Test standards (CEN/TC 341)
Standards for
 Drilling and sampling methods and groundwater measurements
 Laboratory and field tests on soils and rocks
 Tests on structures or parts of structures
 Identification and classification of soils and rocks

Execution of geotechnical works (CEN/TC 288)
Execution standards
 specific design rules (informative annexes)
 specific test procedures

Figure 1.2 — General architecture of the CEN standards linked with EN 1997
1.8 Symbols and units
(1) For the purpose of EN 19972 the following symbols apply.
NOTE The notation of the symbols used is based on ISO 3898:1997.
Latin letters
C_{c}
compression index
c'
cohesion intercept in terms of effective stress
c_{fv}
undrained shear strength from the field vane test
c_{u}
undrained shear strength
C_{s}
swelling index
c_{v}
coefficient of consolidation
C_{α}
coefficient of secondary compression
D_{n}
particle size such that n % of the particles by weight are smaller than that size e.g. D_{10}, D_{15}, D_{30}, D_{60} and D_{85}
E
Young's modulus of elasticity
E'
drained (long term) Young's modulus of elasticity
E_{fdt}
flexible dilatometer modulus
E_{m}
Ménard pressuremeter modulus
E_{meas}
measured energy during calibration
E_{oed}
oedometer modulus
E_{PLT}
modulus from plate loading test
E_{r}
energy ratio (= E_{meas}/E_{theor})
E_{theor}
theoretical energy
E_{u}
undrained Young's modulus of elasticity
E_{0}
initial Young's modulus of elasticity
E_{50}
Young's modulus of elasticity corresponding to 50 % of the maximum shear strength
I_{a}
activity index
I_{c}
consistency index
I_{D}
density index
I_{dmT}
material index from the flat dilatometer test
K_{DMT}
horizontal stress index from the flat dilatometer test
k coefficient of permeability
I_{l}
liquidity index
I_{p}
plasticity index
k_{s}
coefficient of subgrade reaction
m_{v}
coefficient of compressibility
N
number of blows per 300 mm penetration from the SPT
N_{k}
cone factor for CPT, (see equation (
4.1) )
N_{kt}
cone factor for CPTU, (see equation (
4.2) )
N_{10l}
number of blows per 10 cm penetration from the DPL
N_{10M}
number of blows per 10 cm penetration from the DPM
N_{10h}
number of blows per 10 cm penetration from the DPH
N_{10sa}
number of blows per 10 cm penetration from the DPSHA
N_{10sb}
number of blows per 10 cm penetration from the DPSHB
N_{20sa}
number of blows per 20 cm penetration from the DPSHA
N_{30SB}
number of blows per 20 cm penetration from the DPSHB
N_{60}
number of blows from the SPT corrected to energy losses
(N_{1})_{60}
number of blows from the SPT corrected to energy losses and normalized for effective vertical overburden stress
p_{LM}
Ménard limit pressure
q_{c}
cone penetration resistance
q_{t}
cone penetration resistance corrected for pore water pressure effects
q_{u}
unconfined compressive strength
w_{opt}
optimum water content
Greek letters
α
correlation factor for
E_{oed} and
q_{c}, (see Equation (
4.3))
φ
angle of shearing resistance
φ'
angle of shearing resistance in terms of effective stress
µ
correction factor to derive
c_{u} from
c_{fv}, (see Equation (
4.4))
ρ_{d;max}
maximum dry density
σ_{C}
unconfined compression strength of rock
σ_{p} effective preconsolidation pressure or effective vertical yield stress in situ
σ_{T}
tensile strength of rock
σ_{v0} initial vertical total stress
σ_{ν0} initial vertical effective stress
ν
Poisson's ratio
Abbreviations
CPT
electrical cone penetration test
CPTM
mechanical cone penetration test
CPTU
cone penetration test with pore water pressure measurement
DMT
flat dilatometer test
DP
dynamic probing
DPL
dynamic probing light
DPM
dynamic probing medium
DPH
dynamic probing heavy
DPSHA
dynamic probing superheavy, type A
DPSHB
dynamic probing superheavy, type B
FDP
full displacement pressuremeter
FDT
flexible dilatometer test
FVT
field vane test
MPM
Ménard pressuremeter
PBP
prebored pressuremeter
PLT
plate loading test
PMT
pressuremeter test
RDT
rock dilatometer test
SBP
selfboring pressuremeter
SDT
soil dilatometer test
SPT
standard penetration test
WST
weight sounding test
(2) For geotechnical calculations, the following units or their multiples are recommended:
 force kN
 moment kNm
 mass density kg/m^{3}
 weight density kN/m^{3}
 stress, pressure, strength and stiffness kPa
 coefficient of permeability m/s
 coefficient of consolidation m^{2}/s