E1001A-171107
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6. After retrieving the probe, clean the probe (outside and inside) using a nylon brush and
a bucket filled with water.
NOTE : The loading sequence suggested in the ASTM-4719 Standard differs from the
sequence described above. According to the TEXAM developer and manufacturer,
the method described in this manual yields equivalent results
– within normal
accuracy range of the PMT testing in general - while being easier to follow and
slightly more accurate.
7.4 STRESS CONTROLLED TEST
This method is used during a creep test (see below). It can also be used for tests in very
hard soils or in soft rock.
1. Lower the probe to the test depth.
2. Place valve No. 6 on "TEST".
3. Crank until reaching the first pressure step corresponding to about 1/10 of the estimated
limit pressure.
4. Maintain the pressure at this value and record the counter readings 30 seconds, and 60
seconds after the pressure step has been reached. Always stop cranking at least 5
seconds before recording data.
5. When the test is over, slowly return the piston to initial position.
Additional comments:
Pressure step is generally 0.25, 0.5, 1 or 2 bars in soils, and 5 bars in rock. Pressure
step can be estimated with the following relation: Pressure step (bar) = N (blow per
foot) /20. Example if N = 17, start with a 0.5-bar pressure increment.
Check delta V 60 sec
– 30 sec (cc) at each step in order to determine if you are in
the pseudo-elastic zone or in the yielding zone. The first zone is characterized by
rather constant delta V. The second zone is characterized by increasing delta V. If
you still are in the pseudo-elastic zone after 7 steps, double pressure increment.
Adjust pressure steps to try to get 7-14 steps total in the test with at least 2-3 steps
in the yielding zone.
An unload-reload cycle can be done. See instructions above.
Warning: Deflation of the probe must be done slowly
– see warning at section 5.1.
Make sure that the borehole is filled with fluid for helping deflating the probe.
8
PROBE DISASSEMBLY AND ASSEMBLY
DISASSEMBLY :
1- Screw the probe vise adaptor onto one end of the probe and clamp the adaptor in
the jaws of a 4-inch bench vice.
2- Use a strap wrench to unscrew the knurled nut from the free extremity of the
probe.
3- To extract Vulcolan tapered rings, use the extractor provided with the instrument.
Insert and screw in the extractor pins into the two diametrically opposite holes
located on the metal collar of the Vulcolan ring. Rotate the extractor in the
direction of lamination of the metal strips and simultaneously pull the extractor