RD&D-Programme 2004 - SKB

19
9
D=205
d=175
D=172
d=170
D=168
d=106
D=169
F02 P02 F03 F04
P: sensor for total pressure
U: sensor for pore water pressure
W: sensor for relative humidity
3 9
F: inlet to filter
38
U01
P03F05 F10 P06 P07 F12 P08 F13
P01
F01
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
P11
P13 P14
P12 U02
W02
W01
W04
P15 U03
W03
W05
F14
F06 P04 F07 F08 P05 F09 F15 P09 W06 F16 P10 F17
141 100 80 100 120 39 39 120 100 80 100 141
562
2
562
600
600
1,200
Figure 17-3. Cutaway diagram of experimental set-up for the KBS-3H model on a scale of 1:10.
P measurement of swelling pressure, U measurement of pore water pressure, W measurement of
relative humidity, F inlet to filter. The dimensions are in millimetres.
the theoretical calculations, but still fully acceptable. Other results of the model test were that
the perforated outer container burst (as expected) and that a clear effect of the steel could be
seen on the bentonite. The scale test, which lasted one year, also showed that full swelling
pressures developed behind the container but that the pressure variation was greater than in
earlier measurements without a container, see also 17.2.10.
A large-scale Czech experiment (Mock-up Experiment) has been started with support from
SKB. The experiment simulates a deposition hole of the KBS-3V type with buffer and canister
designed for Czech conditions and with the following constituents:
• A rock which is simulated by a steel cylinder with a wall thickness of 8 mm, an inside
diameter of 800 mm and a height of 2,300 mm which is lined with a filter for wetting.
• A canister with an outside diameter of 320 mm and a height of 1,300 mm that contains
two heaters.
• A surrounding buffer that is 160 mm thick between the canister and the steel cylinder.
The buffer is composed of 70 mm high sectoral blocks consisting of a mixture of RMN
bentonite (Czech), ten percent silica sand and five percent graphite.
• A 50 mm wide gap between the bentonite blocks and the filters on the steel cylinder.
The gap is filled with manually compacted buffer of the same composition as the blocks.
Temperature, pressure, relative humidity and strain are measured. The experiment started in
May 2002.
Programme
Model studies
The programme of experimentally investigating the buffer’s thermo-hydro-mechanical
properties will continue, with an emphasis on obtaining values of material parameters for
use in Abaqus and Code Bright. Several of these parameters are difficult to determine and
require calibration and verification tests in the laboratory. For Code Bright in particular, some
numerical and theoretical testing work is needed to be able to use the code’s hydro-mechanical
models in an optimal manner. The doctoral project currently under way to investigate how the
pore pressure potential is affected by mechanical constraint will serve as an important point
of departure for further studies. In particular, parameters having to do with how void ratio
changes affect the pore pressure potential must be determined. Temperature gradient tests
under controlled gas pressure conditions also need to be performed.
214 RD&D-Programme 2004