Euradwaste '08 - EU Bookshop - Europa

sented in the accompanying poster, show a small increment in transmission velocities associated
with micro-crack closure.
a b
Figure 11: a) Example measured waveform and P-wave amplitude ratio (calculated against a reference
survey on ‘undamaged’ sandstone taken at the highest hydrostatic load) b) Waveform and
amplitude ratio for the Wave 3D model that best fits the survey shown in a).
Velocity (m/s)
5000
4500
4000
3500
3000
2500
2000
0 10 20 30
Stage
40 50 60
Vp1
Vp1 model
Vp2
Vp2 model
Vp3
Vp3 model
Vs1
Vs1 model
Vs2
Vs2 model
Vs3
Vs3 model
Crack density
438
0.1
S1
0.09
S2
0.08
S3
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
0 10 20 30 40 50 60
Stage
a b
Figure 12: a) Monitored and EMT modelled transmission velocities in the direction of the three
principal stress axes during the cyclic loading of the Crosland Hill sandstone cube. b) Inverted
crack densities in the three directions.
Velocity change (m/s)
5
0
-5
-10
-15
-20
-25
-30
-35
Vp (DZ)
Vp model (DZ)
Vs (DZ)
Vs model (DZ)
Excavation
-40
0
0 5 10
Time (days)
15 20
10
9
8
7
6
5
4
3
2
1
Excavation depth (m)
Crack density
0.2205
0.2155
0.2105
0.2055
0.2005
0.1955
Crack density
Excavation
0.1905
0
0 5 10
Time (days)
15 20
a b
Figure 13: a) Monitored and modelled (EMT) transmission velocities through a ray path skimming
the surface of SKB’s HRL deposition hole during its excavation. b) Inverted crack densities.
10
9
8
7
6
5
4
3
2
1
Excavation depth (m)