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244 Managing Global Warming

Fig. 7.7 Depressurization method for MH exploitation.

MH and moreover the samples are easily disturbed during transportation. As a result
many previous laboratory tests were performed on artificial samples. In the next sec-
tion the experimental studies of the changes in the mechanical properties of MHBS
during MH dissociation using an improved triaxial apparatus carried out by Hyodo
et al. [18] are described in detail.

7.3 Testing equipment and sample preparation

7.3.1 Triaxial testing apparatus

To reproduce the stress and temperature conditions in the deep seabed and to examine
the mechanical behavior of MH-bearing sand specimens under the conditions at which
MH is produced, a temperature-controlled high pressure triaxial testing apparatus was
developed by Hyodo et al. [18]. With this apparatus the pore pressure and confining
pressure could be controlled under various temperature and high pressure conditions.
Fig. 7.8A shows the physical appearance of the device, while Fig. 7.8B shows a