5
2.3.2 Installation in Mass Concrete
The Model 4430 can be placed directly into concrete or prewired into the rebar cage or
network prior to concrete placement. Tie wires should be connected to the tube rather
than the end blocks and should be perpendicular to the tube and not excessively tight to
allow for shifting during placement of the concrete. The unit has a compressive modulus
of approximately 200,000 psi, and should follow the concrete at very early stages of
curing.
2.3.3 Installation in Fills and Embankments – Soil Strain Gauges
(For more details, see the Model 4435 Soil Strainmeter Manual)
The Model 4435, which is a variation of the Model 4430, is used as a soil deformation
meter in fills and embankments by placing the unit in shallow, horizontal trenches in the
fill. Multiple sensors can be installed in series to give a total deformation profile along a
particular axis as in a dam or highway embankment. Cables issue out of the side of the
devise so that the flanges can be linked together easily.
Downstream
Deformation Meters
Reservoir
Figure 5 - Installation Along Crest of Dam
A narrow flat bottom trench should be excavated in previously compacted fill. The sensor
is laid in the trench and backfilled with material which has had any large (>10 mm, 0.5")
aggregate removed. Backfill and hand tamp the first 15 cm (
≈
6") and then proceed with
the compaction of the fill in the normal way. Cables should also be run in trenches and
backfilled in the same manner as above. For more details, consult the Model 4435 Soil
Strainmeter manual.
Embankment Face
Shear Zone
Horizontal Borehole
Deformation Meters
Figure 6 - Borehole Installation in Embankment