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246 Managing Global Warming

schematic diagram of the testing system. A detailed description of each part shown in
Fig. 7.8B is presented below:
(a) Test specimen
A cylindrical frozen specimen measuring 30 mm in diameter and 50 mm in height, or
50 mm in diameter and 100 mm in height was used.
(b) Pedestal
To prevent the dissociation of natural MH samples, test specimens had to be set up
rapidly. For this purpose, the pedestal in this apparatus was designed to be a one-touch
removable socket-type, as shown in Fig. 7.8C.
(c) Cell

The cell was designed to resist a pressure of 30 MPa, with a mechanism that allowed
cell fluid to circulate internally to control the temperature.
(d) Cell pressure generation device
Cell pressures of up to 30 MPa controllable within the range of 0.1 MPa were sup-
plied by oil pressure.
(e) Inner cell
Because of the possibility for the specimen to become unsaturated during a test, a dou-
ble cell was adopted to measure the volume change. The change in volume could be
obtained by measuring the water level difference in the cell, while the upper part was
opened; however, since high pressures were used, the penetration of the piston in the
sealed-up cylinder controlling the pressure made it possible to measure the volume
change, as shown in Fig. 7.8D.
(f ) Syringe pump for inner cell
To measure the volume change in the inner cell, a cylinder designed to resist pressures
up to 30 MPa was installed and the change in volume inside the cylinder was measured
by controlling the piston in the cylinder via a pulse-controlled method using a stepping
motor. In addition, the change in volume of unsaturated specimens was measured by
correcting the amount of piston penetration, as shown in Fig. 7.8E.
(g) Upper syringe pump
Up till now, high pressure triaxial compression test equipment used in geotechnical
engineering has been used to reproduce the ground stress under high confining pres-
sure. However, the pore water pressure associated with the high pressure condition
needed to reproduce the large depths where MH could exist has not previously been
investigated. To do this, a device similar to the syringe pump for the inner cell
(Fig. 7.8F) was installed. At the extreme condition of 20 MPa, it was possible to con-
trol the pressure to within 0.05 MPa. Moreover, by using an incompressible solution
in the cylinder, the measurement of the volume change of the specimen was possible