Humboldt HM-4160 FlexPanels - Manual (Page 24)

5) Adjust the back pressure, lift Toggle Valve (T2) in section 2 (Base). Increase
pressure by an increment of 5, 10 or 20 psi (35, 70, or 140 kpa).
6) Take Pore Pressure Transducer reading. Monitor for 1 to 2 minutes.
7) Open the Top and Base Drainage Valves on base of Triaxial Cell.
8) Determine the "B" parameter:
The water being pushed into sample can be monitored on Burettes in
Sections 2 (Base) and 3 (Top).
Consolidation of Sample
The following steps should be followed to consolidate the sample after back
pressure saturation.
1) Check the back pressure by lifting the Toggle Valve (T2) under the Pressure
Regulator (R2) in Section 2 (Base) and make any adjustments, if necessary,
then close the Toggle Valve.
2) Check the water level of the Burettes in section 2 (Base) and 3 (Top). The
level should be set near the bottom of the burette so that the volume of
water coming from the sample can be measured.
3) Close the Drainage Valves for the Top and Base on the Triaxial Cell.
4) Raise the effective pressure to the desired consolidation pressure. This is
done by adjusting pressure regulator (R1) to a pressure which equals the
sum of the effective consolidation pressure and the back pressure. To adjust
the pressure lift the Toggle Valve (T1) under the Pressure Regulator (R1) in
Section 1 (Cell). Change the pressure using the Pressure Regulator (R1).
Then close the toggle valve.
5) Take Burette readings for the Base (Section 2) and Top (Section 3). Start
timing and open the Drainage Valves on the Triaxial Cell at the same time.
Take readings on the burettes to monitor rate of consolidation.
Shearing Triaxial
The Following steps should be taken to shear the sample after consolidation.
1) Check the back pressure by lifting the Toggle Valve (T2) under the pressure
Regulator (R2) in Section 2 (Base). Take a reading, do not adjust, close
the Toggle Valve (T2).
2) Check the cell pressure by lifting the Toggle Valve (T1) under the Pressure
Regulator (R1) in Section 1 (Cell)
1. Take reading, do not adjust, then close toggle valve
B =
∆m
∆d
3
∆m = Change in pore pressure
∆d
3
= Change in cell pressure