Users’ Manual
EDS-71V/P Single point borehole extensometer
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3.3.10 When installing a BHE with 50 mm displacement in a vertically downward borehole, settlement is
expected and setting range specified may be – 10/+ 40 mm. In such a case connecting rod end
distance from guide plate top (6) should be set at (45 – 15) i.e. 30 mm.
NOTE:
If readout unit shows negative displacement reading, movement of structure is away from
borehole face and vice versa.
3.3.11 Re-assemble adopter cum guide plate (6) with grub (8.a) and (8.b) taking care that holes marked
‘1’ ‘G’ and ‘V’ are aligned in reference plate (14), adopter cum guide plate (6) and flange housing
(5).
3.3.12 Tighten hollow bolts (12) with spanner size 21 mm and long hollow bolt (12) to firmly grip nylon
tube but not to squeeze or hinder free movement of female end connector inside the nylon tube.
NOTE:
In upward to horizontally sloping borehole, tighten hollow bolts (12) particularly carefully as
grout may leak through into the reference head assembly during the grouting process.
NOTE:
Take care that extensometer assembly does not drop into borehole
accidentally. It is
advisable to secure it properly by attaching a safety rope to the anchor.
3.3.13 Wrap rags or jute cloth strips soaked in quick setting cement water mix outside flanged housing
(5) to build up approximately 5 mm thick layer. Lift and insert housing in borehole using a to and
fro screwing motion sealing the annular space between housing and borehole.
3.3.14 Fix expandable anchors (21) in holes drilled earlier for securing flanged housing with the M12 nuts
and washers provided. Give enough time to let flanged housing set in borehole.
3.3.15 Connect grout pipe to grouting machine or pump, grout till the entire cavity is filled and grout flows
out of air vent pipe. Be very careful that grout flowing out of air vent tube does not get into the
flanged housing and makes the installation messy.
3.3.16 Pump clean water through the grout tube till clear water comes out of air vent tube. This will keep
the grout tube clean for topping up the grout later on.
NOTE:
Give sufficient time for grout to set.
CAUTION:
Clean up grout and air vent tubes with clean water after grouting operation is complete as in
§ 3.3.16 above
NOTE:
Check Engineer for cement water proportion to be used in grout. Composition of grout to be
used depends upon site conditions. In case of hard rock, 50 kg of cement with 30 kg of water
has been successfully used at some project sites.
NOTE:
Grout should cover anchor closest to the mouth or be around 1 m from the face of borehole
whichever distance is less. This can be checked by inserting a
φ
3 mm wire into borehole
through vent pipe.
CAUTION:
Please ensure that no grout overflows into the flanged housing. In case it overflows, it may
get into the protective nylon tubing and jam the setting rods.
3.3.17 Again pump grout into the system after setting period of grout is over to ensure that all anchors
are properly grouted. During setting, heavier grout has a tendency to settle down leaving water at
top with a possibility that anchor is not properly grouted. Rule this possibility out by pumping in
grout again and ensuring that any such water at the top is pumped out through the air vent tube
and replaced by grout.
CAUTION:
To get correct displacement readings, ensure that anchor is properly grouted. This problem
may be particularly faced in case of anchor in downward boreholes and in upward holes where
with cement in grout settling down, there may only be water around the anchor.
