Introduction
Channel networks and sparseness
Nuclear repositories in fractured crystalline rocks
Characterizing and modelling background crystalline rock (BCR)
Guide to the paper
A general formula for percolation applicable to a wide range of geometries
Effects of the shape, size and arrangement of network components on network behaviour
Effect of flow-feature shape
Actively flowing part of the network
Effect of flow-feature size, size distribution and shape
Impact of network organization: orientations of flow-features
Conclusions from evaluation of shape, size and organization on the critical density of networks of flow-features
Measuring the key parameters of a groundwater flow network in BCR
What are the components of a representative network?
Reported measurements of area density
Symbol | Location and rock type | Source | Values of density | Low T threshold (m2 s−1) | |
---|---|---|---|---|---|
I
L
|
A
V
| ||||
K | Kamaishi, Japan: granite | Sawada et al. 2000 | 0.23 fb | 0.46 | ~1 × 10−10 |
M | Mórágy, Hungary: granite | Benedek and Dankó 2009 | 0.09 pb | 0.18 | ~1 × 10−8 |
T | Turkey Creek, USA | Poeter et al. 2003 | ~0.03 | ~1 × 10−6 | |
ML | Mirror Lake, USA: granite | Wellman et al. 2009 | p and f | ~0.02 | ~1 × 10−5 |
O1 | Olkiluoto, Finland: basement below −400 masl | Table 4.8 of Hartley et al. 2012 (NHU domain surface boreholes only) | 0.01 pfla | 0.02 | ~1 × 10−9 |
O2 | Olkiluoto: + underground | Table 10.4 of Hartley et al. 2012 | 0.19 pfla | 0.39 | ~1 × 10−11 |
F | Forsmark, Sweden: granite | Table 3 of Follin et al. 2014 | 0.005 pfla | 0.01 | ~5 × 10−10 |
Ӓ | Ӓspö, Sweden: granite (TRUE Block TTV region) | Table 5.2 of Andersson et al. 2002 | 0.19 pfla | 0.29 | ~1 × 10−10 |
S | Stripa, Sweden: granite | Holmes 1989 (SCV) | 0.34 pb | 0.68 | ~1 × 10−11 |
L | Laxemar, Sweden, granite | Table 9–14 of Rhén et al. 2008 | 0.008 pfla | 0.016 | ~1 × 10−10 |
W | Sellafield, UK: ignimbrite | Degnan et al. 2003 based on flow-features | ~0.1 fb | 0.2 | ~5 × 10−10 |
Wc | Sellafield, UK: ignimbrite | Degnan et al. 2003 based on flow-features in clusters | ~0.01 fb | 0.02 | ~5 × 10−10 |
Symbol | Location and fracture type | Source | Method | Density | |
---|---|---|---|---|---|
I
L
| AV | ||||
K | Kamaishi, Japan: open fracs | Sawada et al. 2000 | Borehole TV | 1.0b | 2 |
O3 | Olkiluoto, Finland: fracture traces below −400 m asl | Table 4.8 of Hartley et al. 2012 (NHU domain) | Borehole corea | 2.3b | 4.6 |
O4 | Olkiluoto, open fractures | Table 4.8 of Hartley et al. 2012 (NHU domain) | Borehole corea | 0.7b | 1.4 |
O5 | Olkiluoto: open fractures | Table 10.4 of Hartley et al. 2012 (NHU domain) + underground boreholes | Core+ TVa | 0.43b | 0.85 |
F | Forsmark, Sweden: open fractures | Table 3 of Follin et al. 2014 | Core+TV | 0.54 | 1.1 |
Sv | Stripa, Sweden: fracture traces | Rouleau and Gale 1985 | Core logs | 6.4b | 12.8 |
L | Laxemar, Sweden: open fractures | Table 10–2 of Rhén et al. 2008 | Core logs | 1.9b | 3.7 |
Ӓ > 1 m | Ӓspö, Sweden: all fractures >1 m | Table 2.10 of Bossart et al. 2001 | Tunnel map | 0.55a | 0.7 |
Ӓ > 0.3 | Ӓspö, Sweden: all fractures >0.3 m | Table 2.10 of Bossart et al. 2001 | Tunnel map | 1.27a | 1.6 |
Reported measurements of the size and shape of flow-features/channels
Plates, flow-features and channels
Channel size: extensiveness or ‘length’
Channel width
Transmissivity distribution
Constraining the range of size-shape combinations
-
Groundwater flow in BCR occurs within a sparse network of flow-features that is at or just above critical density: an assumption that agrees with the views expressed by Chelidze (1982) and Renshaw (1996). Thus, a measurement of area density in situ is likely to yield a value of area density close to critical density.
-
PFL results are a measure of the area density of the active flow system plus any dead-end clusters that connect to the test borehole.
-
Detailed packer test results are a measure of the area density of all possible flow-features.
Discussion
A possible strategy for parameterizing and modelling groundwater flow in BCR
Methodology and precepts
Field measurements
Constructing an appropriate lattice model
Parameters for ellipse model | Common parameters | Equivalent parameters for lattice model | |||||
---|---|---|---|---|---|---|---|
a
|
b
| ρc(a/b) | nc(a,b) | Bc(a/b) | Lc(a/b) | Gc(a/b) | Δc(a,b) |
1 | 1 | 8.14 | 0.233 | 2.30 | 1.10 | 2.73 | 1.50 |
2 | 1 | 8.14 | 0.0726 | 2.21 | 1.16 | 3.08 | 2.14 |
4 | 1 | 8.14 | 0.0185 | 2.00 | 1.37 | 4.26 | 3.07 |
8 | 1 | 8.14 | 0.00423 | 1.74 | 1.74 | 6.88 | 4.35 |
16 | 1 | 8.14 | 0.00092 | 1.50 | 2.38 | 12.81 | 5.97 |
32 | 1 | 8.44 | 0.00021 | 1.33 | 3.21 | 23.32 | 8.18 |
64 | 1 | 9.04 | 0.00005 | 1.22 | 4.21 | 40.18 | 11.25 |
1.244 | 0.343 | 8.14 | 0.561 | 2.03 | 1.331 | 4.019 | 1 |