4
9)
To set the range of the transducer, take the end of the
connecting rod
(Item 12) protruding
out the back of the flange and pull it to the desired percentage of the range, either by
measuring the distance the rod was pulled, or by recording the reading of the sensor while
pulling on the connecting rod (preferred method). Make sure not to overextend the rod or
rotate it beyond 180 degrees as this may damage the sensor. Tighten the
setscrews
(Item 17)
in the rod end flange to lock the sensor's position in place. Any excess rod protruding out of
the back can be sawed off at this point, if needed.
10)
Install the assembly, and then loosen the nylon setscrews. Take baseline zero readings for
comparison.
2.3 Deformation Meter Installation
2.3.1 Installation in Boreholes
The primary use of the Model 4430 is for the measurement of axial strains or
deformations in boreholes. The most common method of installation is by grouting.
Horizontal holes should be inclined slightly downward to make for easy grouting and to
avoid air pockets. Vertical up holes require special grouting apparatus and snap ring or
hydraulic anchors on the gauge to hold it in place while grouting the hole.
Horizontal and vertical down holes are instrumented as follows:
Drill the borehole at least 0.5 meters (
≈
two feet) beyond the location of the deepest
flange. The borehole must be a minimum of 60 mm (2.25") in diameter. Fill the hole with
grout mixture of one part Portland cement to one to two parts water by volume. An
expansive mix is helpful particularly in horizontal holes. Lower or push the sensor(s)
down the hole to the proper location as noted by a mark on the cable. If more than one
sensor is to be placed in a hole, be sure to maintain the position of the lower sensor while
installing shallower ones.
Grout
Instrument Cable
Deformation Meter
Fault
Borehole
Figure 4 - Borehole Installation
For situations such as soft ground or when the hole is cased and casing must be
withdrawn, it may be advisable to use a sensor with a hydraulic anchor for permanent
positioning. This should be discussed with the application engineers at the factory.