Annex A
(informative)
Example of a flow chart for the selection of ground investigation methods in different phases
ANNEX B.1
(informative)
Cone Penetration Test (CPT)
(1) Table B.1 is an example of derived values, from the value of qc, of the angle of shearing resistance N' and drained (long term) Young's modulus Em for quartz and feldspar sands, for calculations of the bearing capacity and settlement of spread foundations.
(2) This example correlates the mean value of qc in a layer to the mean values of N' and Em (see subclause 1.3.2).
| Relative density | Cone resistance (qc) [MPa] (from CPT-test) |
Angle of shearing resistance1) (N') | Drained Young's modulus2) (Em) [MPa] |
| very low low medium high very high |
0,0—2,5 2,5—5,0 5,0—10,0 10,0—20,0 >20,0 |
29—32 32—35 35—37 37—40 40—42 |
<10 10—20 20—30 30—60 60—90 |
| 1) Values given are valid for sands. For silty soils a reduction of 3° should be made. For gravels 2° should be added. 2) Values given for the drained modulus correspond to settlements for 10 years. They are obtained assuming that the vertical stress distribution follows the 2:1 approximation. Furthermore, some investigations indicate that these values can be 50 % lower in silty soils and 50 % higher in gravelly soils. In overconsolidated cohesionless soils the modulus can be considerably higher. When calculating settlements for ground pressures greater than 2/3 of the design bearing pressure in ultimate limit state, the modulus should be set to half of the values given in this table. |
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For additional information and documents giving examples, see Annex M.
ANNEX B.2
(informative)
Cone Penetration Test (CPT)
(1) The following is an example of a semi-empirical method for calculating settlements of spread foundations in cohesionless soils (after Schmertmann, 1970).
(2) The settlement s of a foundation under load pressure q is expressed as:
where:
C1 is 1 - 0,5[σ'v0/(q − σ'v0)];
C2 is 1,2 + 0,2 · logt;
σ'v0 is the initial effective vertical stress at the level of the foundation;
t is the time, in years.
(3) Figure B.1 gives for axisymmetric (circular and square) spread foundations and for plane strain (strip spread foundations) the distribution of the vertical strain influence factor Iz. The derived value for Young's modulus Em to be used in this method is:
- Em = 2,5 × qc, for axisymmetry, and
- Em = 3,5 × qc, for plane strain.
For additional information and examples see Annex M.
ANNEX B.3
(informative)
Cone Penetration Test (CPT)
(1) The following is an example of derived values of " for various types of soils (after Sanglerat, 1972)
| CL - low-plasticity clay: | qc < 0,7 [MPa] 0,7 < qc < 2 [MPa] qc > 2 [MPa] |
3 < α < 8 2 < α < 5 1 < α < 2,5 |
| ML - low-plasticity silt: | qc < 2 [MPa] qc ≥ 2 [MPa] |
3 < α < 6 1 < α < 2 |
| CH - very plastic clay MH - very plastic silt: | qc < 2 [MPa] qc > 2 [MPa] |
2 < α < 6 1 < α < 2 |
| OL - very organic silt: | qc < 1,2 [MPa] | 2 < α < 8 |
| T-OH-peat and very organic clay: | qc < 0,7 [MPa] 50 < w ≤ 100 100 < w ≤ 200 w > 300 |
1,5 < α < 4 1 < α < 1,5 α < 0,4 |
| Chalks: | 2 < qc ≤ 3 [MPa] qc > 3 [MPa] |
2 < α < 4 1,5 < α < 3 |
| Sands: | qc < 5 [MPa] qc > 10 [MPa] |
α = 2 α = 1,5 |
For additional information and examples see Annex M.
