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NUMERICAL METHODS IN GEOTECHNICAL ENGINEERING APPLICATIONS 2-3 Design of the Pont Ventoux – Finestra 2 tunnel Geotechnical characterisation of the site

Refernces: chapters 3 and 4 + schede 1-7 AIM & SCOPE: The aim of these applications is to determine the intact rock and rock mass characteristics on the basis of laboratory test results and geomechanical classification (both Hoek & Brown and Mohr-Coulomb peak and residual parameters).

A number of laboratory tests were carried out on samples of micaschists, obtained from boreholes 2S13i and 2S14i (see location of the boreholes on Figure 1) comprising:

- Unconfined compression tests (Table 1) - Triaxial compression tests (Table 2 and 3) - Brasilian tensile strength tests (Table 4)

For additional reference, data from two selected tests ROC240 (Data sheet 1) and ROC225 (Data sheet 2) are given in graphical form.

Students are requested to do the following:

a) Determine the intact rock peak and residual strength parameters by using the Hoek & Brown

failure criterion, on the basis of the data given in Tables 1, 2, 3, 4 and 5.

b) Determine the intact rock peak and residual strength parameters by using the Mohr-Coulomb

failure criterion by linearization of the Hoek & Brown failure criterion. Reference should be made to the recommendations given by Hoek & Brown (1997) for appropriate choice of the minimum principal stress range (i.e. 8 values of σ3 between 0 and 0.5 times the intact rock unconfined compressive strength).

c) Determine the rock mass peak strength, residual strength and deformability parameters

making reference to the rock mass classification at cross section 011 (Data sheet 3).

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Figure 1. Boreholes location

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Table 1. Unconfined compression tests on samples from boreholes 2S13i e 2S14i

Sond. Sigla Prof. I H Φ σ Eds Edt νs νt

[m] [gradi] [mm] [mm] [MPa] [MPa] [MPa] 2S14i ROC218 472.0 60/70 87.8 47.4 140.05 38760 61400 0.09 0.20 2S14i ROC219 481.0 70/80 92.0 47.4 164.63 47630 67160 0.10 0.15 2S14i ROC220 492.0 90 92.4 47.6 174.20 51600 64560 0.16 0.27 2S14i ROC221 502.8 90 90.8 48.2 162.15 41560 63260 0.12 0.24 2S14i ROC222 504.8 70/80 93.2 47.6 153.15 44720 60530 0.13 0.24 2S14i ROC223 521.8 90 93.2 47.4 160.80 32950 56820 0.08 0.20 2S13i ROC239 376.1 35/40 94.3 47.4 90.81 45140 50580 0.19 0.27 2S13i ROC240 376.4 50 95.0 47.4 85.20 44210 51320 0.19 0.26 2S13i ROC241 376.7 40 94.3 47.5 105.88 43790 54120 0.18 0.30 2S13i ROC242 392.0 50 92.5 47.3 64.47 45960 51560 0.21 0.29 2S13i ROC243 419.0 45 91.8 47.2 43.15 29090 36850 0.09 0.27 2S13i ROC244 448.4 45 93.5 47.4 65.81 43650 50440 0.14 0.26

Table 2. Triaxial tests on samples from boreholes 2S13i

Sond. Sigla Prof. I H Φ σrad σ σres Eds Edt νs νt

[m] [gradi] [mm] [mm] [MPa] [MPa] [MPa] [GPa] [GPa]

2S13i ROC224 282.0 40 121.5 63.4 2.5 90.35 18.38 51.29 55.9 0.05 0.18

2S13i ROC225 295.0 40 123.9 63.0 5 62.24 23.12 60.01 63.45 0.10 0.19

2S13i ROC226 304.5 45 124.4 63.3 7.5 91.24 44.1 63.5 61.55 0.11 0.18

2S13i ROC227 303.3 40 123.9 63.3 10 131.19 56.73 68.81 61.52 0.13 0.19

2S13i ROC228 307.5 40 122.6 63.4 12 68.64 47.42 44.5 45.54 - 0.08

2S13i ROC229 310.0 45 123.8 63.3 12 201.76 87.48 62.45 68.9 0.19 0.3

2S13i ROC230 312.5 40 121.3 63.4 5 77.43 34.19 36.67 41.42 - 0.32

2S13i ROC231 319.4 30/40 123.3 63.3 7.5 125.6 54.41 49.44 58.15 0.05 0.07

2S13i ROC232 323.4 50 122.4 63.3 10 79.6 64.7 25.76 27.43 - 0.1

2S13i ROC233 338.6 40 123.6 63.4 2.5 67.83 21.07 34.78 39.72 - 0.19

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Table 3. Triaxial tests on samples from boreholes 2S14i

Sond. Sigla Prof. I H Φ σrad σ σres Eds Edt νs νt

[m] [gradi] [mm] [mm] [MPa] [MPa] [MPa] [MPa] [MPa]

2S14i ROC174 298.0 70/90 125.6 63.5 2.5 145.04 26.95 41770 60360 0.10 0.18

2S14i ROC175 298.5 70/90 122.6 63.5 5.0 166.08 38.39 57190 63730 - -

2S14i ROC176 335.7 60 124.1 63.3 7.5 91.25 36.66 41610 48690 0.09 0.20

2S14i ROC177 342.8 55 123.4 63.4 10.0 122.48 59.00 51710 59180 - 0.07

2S14i ROC178 342.2 70 123.1 63.4 12.0 176.76 77.22 57560 63350 0.08 0.10

2S14i ROC179 354.2 70-80 123.1 63.4 2.5 143.78 22.60 52280 63270 0.09 0.15

2S14i ROC180 369.4 80 124.5 63.4 5.0 177.54 54.25 49400 60420 0.06 0.24

2S14i ROC181 369.6 70 123.4 63.4 7.5 155.97 49.20 40170 56240 0.05 0.13

2S14i ROC182 376.8 45 123.9 63.5 10.0 137.75 67.80 70310 71760 - -

2S14i ROC183 395.0 45 124.3 63.4 12.0 193.33 62.11 66120 65260 0.10 0.25

Table 4. Brasilian tensile strength tests

Sond. Sigla Prof. H Φ σt

[m] [mm] [mm] [MPa]2S14i ROC184 349.9 46.3 62.8 14.532S14i ROC185 365.8 47.0 62.9 02.582S14i ROC186 371.1 44.6 62.9 22.292S14i ROC187 374.7 44.1 62.9 19.332S14i ROC188 379.0 48.8 63.0 19.182S13i ROC234 325.4 47.1 62.8 15.232S13i ROC235 336.2 47.5 62.8 14.482S13i ROC236 334.0 49.8 62.9 7.37 2S13i ROC237 339.0 47.6 62.9 7.43 2S13i ROC238 343.8 51.0 62.9 8.35

Legenda:

I: angle of the schistosity with respect to the core axis

H: height

Φ: diameter

σ: axial stress (peak value)

σrad : confinement stress

σres : residual strength

σt : tensile strength

Eds: deformation modulus (secant)

Edt: deformation modulus (tangent)

νs: Poisson’s ratio (secant)

νt: Poisson’s ratio (tangent)

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Data sheet 1 - Borehole 2S13i – Specimen ROC 240/28 - Depth 376.40 m

Unconfined compression test

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Data sheet 2 - Borehole 2S13i – Specimen ROC 225/12 - Depth 295.00 m

Triaxial compression test (confining pressure 5.0 MPa)

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Data sheet 3 GEOMECHANICAL CLASSIFICATION

Tunnel: F2-Pont Ventoux

Geo-structural survey n°: 011

Chainage: 876 - 891 m

Bieniawski classification parameters and numerical coefficients:

1) Unconfined compression test: 86-153 MPa n1 = 9

2) Rock Quality Designation RQD: 76 % n2 = 15

3) Joint spacing: 0,97 m n3 = 14

4) Joint conditions (roughness) n4 = 25

5) Water inflow in 10 m of tunnel: minor along J1 n5 = 8

6) Joint orientation: unfavourable n6 = -7

RMR = 64