Users’ Manual
EDS-71V/P Single point borehole extensometer
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1 INTRODUCTION
Encardio-rite model EDS-71V single point borehole extensometer using vibrating wire sensors is a
precision instrument designed to help civil engineers and geologists in measurement of deformation of rock
mass and adjacent or surrounding soil. Together with anchor bolt load cells and tape extensometer, it is
an essential piece of equipment for investigation and monitoring of foundations, slopes & embankments
and for studying behaviour of rock around underground cavities, tunnels and mines.
NOTE:
Same manual to be used for model EDS-71P single point borehole extensometer using
potentiometric sensors. Make special note of the following:
Diameter of model EDE-PXX potentiometric sensor is 16 mm whereas diameter of Model EDE-VXX is
12.7 mm. This requires adaptor cum guide plate (6) and link plate (16) in figure 2.2 to be different in
the two assemblies.
Manual readout unit for EDE-PXX is model EDI-53P, whereas for model EDE-VXX is model EDI-51V.
For Sample test certificate of model EDE-PXX refer to page 3-3. Sample test certificate for model EDE-
VXX is given on page 3-2.
1.1 Applications
To determine how roof or wall of mine, underground cavity or tunnel behaves during excavation.
To study effectiveness of the roof/wall support system of a mine, underground cavity or tunnel.
To predict potential roof or wall falls before they actually occur. Roof or wall falls in underground cavities
are almost invariably preceded by measurable sags as the strata opens up and the movement usually
occurs at an increasing rate as fall conditions are approached. Unsuspected roof and wall falls may
result in serious accidents and may require costly patch-up and repair operations.
To measure and monitor movements in slopes and foundations due to excavation of underground
cavities or due to construction of heavy structures like concrete, rockfill, masonry or earth dams over
the foundation.
Suitable for upward or downward sloping hole using fibreglass or stainless steel AISI-410 connecting
rods.
Model EDS-71V/P has following options:
Required borehole for installation of single point extensometers is
φ
50 mm. Diameter at the mouth of
borehole is increased to 63 mm (300 mm depth for 50 mm displacement sensor or 430 mm depth for
100 mm displacement sensor and 560 mm for 150 mm displacement sensor).
The displacement is measured electronically by using a vibrating wire displacement transducer model
EDE-VXX and a readout system model EDI-51V or data acquisition system model EDAS-10. The
displacement is measured using potentiometric sensor model EDE-PXX with an indicator EDI- 53P
1.2 Measurement method
The displacement is measured electronically by using a vibrating wire displacement transducer model
EDE-VXX and Potentiometric displacement transducer model EDE-PXX with read out system model EDI-
51V and EDI-53P respectively or data acquisition system model EDAS-10.
