RST Instruments VW2100, Instruction Manual, Page: 17 / 34

VW2100 Vibrating Wire Piezometer
Instruction Manual
ELM0005P RST Instruments Ltd. Page 17
applied to the piezometer tip to maintain the saturation level. The plastic cap
must be removed immediately before installation.
CAUTION: V
IBRATING WIRE PIEZOMETERS CANNOT BE ALLOWED TO FREEZE WHEN
FULLY SATURATED
,
OTHERWISE DAMAGE WILL OCCUR TO THE TRANSDUCER
DIAPHRAGM
,
WHICH WILL INVALIDATE THE TRANSDUCER FUNCTION AND
CALIBRATION
.
5.4 I
NSTALLATION IN
F
ULL
5.4.1 Compacted Clay
1
Excavate a vertical trench or recess approximately 50 cm deep in the clay
material. Form a horizontal cylindrical hole in the sidewall of the excavated trench
near the bottom. The hole diameter should be slightly smaller than the
piezometer body to ensure a snug fit when the piezometer is inserted in the hole.
2
Push the piezometer into the hole in the trench side, and into the host clay
material. Smear the filter ceramic with a thin paste of the saturated clay material
if necessary, to ensure continuity of the saturated air entry filter and pore water.
3
Place the cable with the utmost care to avoid any damage due to kinking or
stretching. Look the cable and route it out of the trench. Make sure it rests on a
bed of hand placed and lightly compacted screened clay. Ensure that the cable
does not come into direct contact with itself or other cables in the area. Always
maintain a few centimeters of compacted clay material between any two cables.
4
Backfill the trench with screened clay containing no particles larger than 3 mm in
dimension. The backfill should have a water content and density equal to that of
the surrounding material.
5
Ensure that the cable is well protected from any potential damage caused by any
angular fill material, compacting equipment, and any settlement that might occur
due to construction work or subsequent fill placement.
5.4.2 Granular Materials
1
Excavate a vertical trench or recess about 50 cm deep in the granular material.
2
Place the piezometer horizontally in the center of the trench or recess.
3
Loop the cable and backfill the bottom 10 cm of the trench around the piezometer
with screened granular material not exceeding 3 mm in dimension.
4
Above that level, the trench can be backfilled in 10 cm lift with the same granular
material that was excavated. The granular backfill should contain the same
moisture content and be compacted to the same density as the surrounding fill.
Care must be exercised to not subject the piezometer instrument to damage
during compaction work.