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 *q*_{c}, of the angle of shearing resistance *N*' and drained (long term) Young's modulus *E*_{m} for quartz and feldspar sands, for calculations of the bearing capacity and settlement of spread foundations.

**(2)** This example correlates the mean value of *q*_{c} in a layer to the mean values of *N*' and *E*_{m} (see subclause 1.3.2).

*N*' and drained Young's modulus

*E*

_{m}for quartz and feldspar sands from cone resistance

*q*

_{c}(after Bergdahl et al. 1993)

Relative density | Cone resistance (q_{c})[MPa] (from CPT-test) |
Angle of shearing resistance^{1)} (N') |
Drained Young's modulus^{2)} (E_{m})[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. |

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:

*C*_{1} is 1 - 0,5[σ'_{v0}/(*q* − σ'_{v0})];

*C*_{2} is 1,2 + 0,2 · log*t*;

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 *I*_{z}. The derived value for Young's modulus *E*_{m} to be used in this method is:

*E*_{m}= 2,5 ×*q*_{c}, for axisymmetry, and*E*_{m}= 3,5 ×*q*_{c}, 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: | q_{c} < 0,7 [MPa]0,7 < q_{c} < 2 [MPa]q_{c} > 2 [MPa] |
3 < α < 8 2 < α < 5 1 < α < 2,5 |

ML - low-plasticity silt: | q_{c} < 2 [MPa]q_{c} ≥ 2 [MPa] |
3 < α < 6 1 < α < 2 |

CH - very plastic clay MH - very plastic silt: | q_{c} < 2 [MPa]q_{c} > 2 [MPa] |
2 < α < 6 1 < α < 2 |

OL - very organic silt: | q_{c} < 1,2 [MPa] |
2 < α < 8 |

T-OH-peat and very organic clay: | q_{c} < 0,7 [MPa]50 < w ≤ 100100 < w ≤ 200w > 300 |
1,5 < α < 4 1 < α < 1,5 α < 0,4 |

Chalks: | 2 < q_{c} ≤ 3 [MPa]q_{c} > 3 [MPa] |
2 < α < 4 1,5 < α < 3 |

Sands: | q_{c} < 5 [MPa]q_{c} > 10 [MPa] |
α = 2 α = 1,5 |

For additional information and examples see Annex M.