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Erschienen in:
23.01.2018 | Technical Note
Effect of Thermal Treatment on Brazilian Tensile Strength of Granites with Different Grain Size Distributions
Erschienen in: Rock Mechanics and Rock Engineering | Ausgabe 4/2018
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Excerpt
Since the first enhanced geothermal system (EGS) was conceived at the Fenton Hill project, the USA, in the 1970s, EGS projects have been pursued around the world (McClure and Horne 2014). EGS projects involve finding vast blocks with high-temperature (> 200 °C) and fracture systems. Water is first injected and circulated through the fracture networks in geothermal reservoirs and eventually pumped back to the surface as steam. EGS projects are commonly located in granite rocks with various mineralogical properties (Table 1). The mechanical response of “hot granites” to cooling becomes an important question to geologists and engineers.
Table 1
The mineralogical properties of granites in worldwide EGS sites
|
EGS sites
|
Minerals* (%)
|
Grain sizes
|
||||
|---|---|---|---|---|---|---|
|
Qtz
|
Pl
|
Fsp
|
Mi
|
Others
|
||
|
Basel, Switzerland
|
26.0
|
34.5
|
12.2
|
16.1
|
11.2
|
(1) Coarser-grained at the top of the basement
(2) Finer-grained at deeper borehole sections
|
|
Cooper basin, Australia
|
31
|
31
|
31
|
5
|
2
|
0.05–0.2 mm
|
|
Desert Peak, USA
(Lutz et al. 2004)
|
22–28
|
37–42
|
14–19
|
3–5
|
Medium to coarsely crystalline
|
|
|
Fenton hill, USA
(Laughlin et al. 1983)
|
32
|
31
|
−
|
6
|
(microcline) 28
|
Medium to coarse
|
|
Fjäillbacka, Sweden
|
27–29
|
43–44
|
−
|
6–8
|
(microcline) 27–31
|
Fine- to coarse-grained
|
|
Ogachi, Japan
(Ueda et al. 2005)
|
45.2
|
11.5
|
19.8
|
−
|
23.5
|
Fine-grained, grain size from 0.1 to 1.7 mm
|
|
Rosemanowes, UK
(Charoy 1986)
|
30
|
30
|
30
|
−
|
10
|
The grain size of quartz is up to 1 mm
|
|
Soultz, France
|
22
|
43
|
25
|
6
|
4
|
Between 300 and 500 μm
|
|
Habanero, Japan
(Chen and Wyborn 2009)
|
Innamincka granite and is comprised of 75% SiO2 and > 5% K2O
|
Medium- to coarse-grained
|
||||