Geokon 1100 User manual

Instruction Manual
Model 1100
Borehole Extensometer
No part of this instruction manual may be reproduced, by any means, without the written consent of GEOKON®.
The information contained herein isbelieved tobe accurate and reliable. However, GEOKON®assumes no responsibility for
errors, omissions, or misinterpretations.The information herein is subject to change without notification.
Copyright © 2022 by GEOKON®(Document Revision A.1, 05/01/2023)

Warranty Statement
GEOKON warrants its products to be free of defects in materials and workmanship, under
normal use and service for a period of 13 months from date of purchase. If the unit should
malfunction, it must be returned to the factory for evaluation, freight prepaid. Upon examination
by GEOKON, if the unit is found to be defective, it will be repaired or replaced at no charge.
However, the WARRANTY is VOID if the unit shows evidence of having been tampered with
or shows evidence of being damaged as a result of excessive corrosion or current, heat, moisture
or vibration, improper specification, misapplication, misuse or other operating conditions outside
of GEOKON's control. Components which wear or which are damaged by misuse are not
warranted. This includes fuses and batteries.
GEOKON manufactures scientific instruments whose misuse is potentially dangerous. The
instruments are intended to be installed and used only by qualified personnel. There are no
warranties except as stated herein. There are no other warranties, expressed or implied, including
but not limited to the implied warranties of merchantability and of fitness for a particular
purpose. GEOKON is not responsible for any damages or losses caused to other equipment,
whether direct, indirect, incidental, special or consequential which the purchaser may experience
as a result of the installation or use of the product. The buyer's sole remedy for any breach of this
agreement by GEOKON or any breach of any warranty by GEOKON shall not exceed the
purchase price paid by the purchaser to GEOKON for the unit or units, or equipment directly
affected by such breach. Under no circumstances will GEOKON reimburse the claimant for loss
incurred in removing and/or reinstalling equipment.
Every precaution for accuracy has been taken in the preparation of manuals and/or software,
however, GEOKON neither assumes responsibility for any omissions or errors that may appear
nor assumes liability for any damages or losses that result from the use of the products in
accordance with the information contained in the manual or software.

1THEORY OF OPERATION .................................................................................................................... 1
1.1 INTRODUCTION....................................................................................................................................................1
1.2 SYSTEM COMPONENTS..........................................................................................................................................1
1.2.1 Head Assembly.......................................................................................................................................2
1.2.2 Coupling, Standpipe, and Flange ...........................................................................................................3
1.2.3 Vibrating Wire Displacement Transducers ............................................................................................4
1.2.4 Connecting Rods ....................................................................................................................................5
1.2.5 Borehole Anchors...................................................................................................................................6
2INSTALLATION CONSIDERATIONS ....................................................................................................... 9
2.1 TOOLS................................................................................................................................................................9
2.1.1 P/N 1100-TOOLKIT (Set of installation tools).........................................................................................9
2.1.2 P/N 1100-RECESSED-TOOLS (Accessories for recessed installations)...............................................9
2.1.3 P/N 1100-GROUT-DOWN (Accessories for inclined downward installations) ....................................9
2.1.4 P/N 1100-GROUT-UP (Accessories for overhead/upward installations) .............................................9
2.2 BOREHOLE DIAMETER .........................................................................................................................................10
2.2.1 Extensometers without an Over Core ..................................................................................................10
2.2.2 Extensometers Recessed in an Over Core Borehole .............................................................................11
2.3 ANCHOR SPACING ..............................................................................................................................................13
2.4 CABLE INSTALLATION AND SPLICING .......................................................................................................................13
3ASSEMBLY AND INSTALLATION .........................................................................................................15
3.1 PREPARATION....................................................................................................................................................15
3.2 CONNECTING ROD ASSEMBLY...............................................................................................................................15
3.2.1 Stainless Steel Connecting Rods...........................................................................................................15
3.2.2 For All Anchor Types: ...........................................................................................................................19
3.2.3 Fiberglass Connecting Rods .................................................................................................................20
3.3 ATTACH EXTENSION RODS TO CONNECTING ROD COLUMN ........................................................................................20
3.4 INSTALL HYDRAULIC LINES (HYDRAULIC ACTUATED ANCHORS ONLY)............................................................................21
3.5 BUNDLE THE RODS AND ANCHORS TOGETHER..........................................................................................................21
3.6 INSTALL GROUT PIPE (GROUTED BOREHOLES/CASING ONLY) .....................................................................................21
3.7 PVC STANDPIPE AND COUPLING ASSEMBLY ............................................................................................................21
3.8 FLANGE INSTALLATION ........................................................................................................................................21
3.9 LIFTING THE EXTENSOMETER ASSEMBLY INTO THE BOREHOLE .....................................................................................22
3.10 SETTING ANCHORS.........................................................................................................................................22
3.10.1 Groutable Anchors ..........................................................................................................................22
3.10.2 Hydraulic Anchors (Bladder and Borros Style) ................................................................................23
3.11 REMOVE ANCHOR HARDWARE.........................................................................................................................23
3.12 ATTACH THE TRANSDUCER HOUSING ASSEMBLY ..................................................................................................24
3.13 INSTALLING THE VIBRATING WIRE TRANSDUCERS.................................................................................................24
3.14 INSTRUMENT HEAD PROTECTION ......................................................................................................................26
4TAKING READINGS ...........................................................................................................................26
4.1 ELECTRONIC READINGS........................................................................................................................................26
4.1.1 Readout Box.........................................................................................................................................26
5TROUBLESHOOTING.........................................................................................................................27
APPENDIX A. SPECIFICATIONS....................................................................................................................28
A.1 MODEL 1100 SPECIFICATIONS .................................................................................................................................28
A.2 ROD SPECIFICATIONS..............................................................................................................................................28
A.3 MODEL 4450 VIBRATING WIRE TRANSDUCER SPECIFICATIONS.......................................................................................28
A.4 HEAD ASSEMBLY DIMENSIONS .................................................................................................................................29
APPENDIX B. THERMISTOR TEMPERATURE DERIVATION ..............................................................................31
APPENDIX C. WIRING CHARTS FOR VIBRATING WIRE TRANSDUCERS .............................................................32

C.1 SINGLE TRANSDUCER WIRING CHART .........................................................................................................................32
C.2 TWO TRANSDUCER WIRING CHART............................................................................................................................32
C.3 THREE TRANSDUCERS WIRING CHART ........................................................................................................................32
C.4 FOUR TRANSDUCERS WIRING CHART .........................................................................................................................32
C.5 FIVE TRANSDUCERS WIRING CHART ...........................................................................................................................33
C.6 SIX TRANSDUCERS WIRING CHART.............................................................................................................................34
APPENDIX D. SWAGELOK TUBE FITTING INSTRUCTIONS............................................................................... 35
D.1 INSTALLATION .......................................................................................................................................................35
D.2 REASSEMBLY INSTRUCTIONS .....................................................................................................................................36
APPENDIX E. GUIDE TO ORDERING EXTENSOMETERS................................................................................... 36

1
1 THEORY OF OPERATION
1.1 Introduction
Borehole extensometers are used for monitoring displacements along the axis of the instrument
in various applications (tunnels, shoring sidewalls, earthen dams, landslides, etc.) A series of
borehole anchors interconnected by fiberglass, composite/graphite, or stainless steel connecting
rods are installed at predetermined depths, with the deepest anchor installed in stable ground to
serve as a nonmoving reference point. If a stable point cannot be established with the deepest
anchor, the head of the extensometer can serve as the reference point but must be tied into an
external survey system.
Each borehole anchor is typically coupled to a Vibrating Wire (VW) Displacement Transducer to
measure the movement in each zone relative to the head. Anchor movements are sensed
electronically with transducers or mechanically determined with a dial gauge where applicable,
and a measurement of the position of the top of connecting rod relative to the anchor is
determined. This not only enables the measurement of the magnitude of any movements but also
narrows down the identification of zones of movements.
To ease installation, the extensometer should be assembled on the ground next to the borehole
and then suspended and lowered into the borehole. The anchors are then set in place, either by
applying hydraulic pressure (borros and bladder type anchors) or using cement grout
(groutable anchors).
1.2 System Components
The four basic components of the extensometer are: the head assembly, Vibrating Wire
Displacement Transducers (contained within the head assembly), connecting rods and tubing,
and the borehole anchors. Each of these components are described in the sections that follow.

2
1.2.1 Head Assembly
Figure 1 - Four Main Components of the Extensometer

3
The extensometer head assembly houses and protects the VW displacement transducers.
The head assembly includes the following components:
•Protective cap
•Side-exit cable (custom top exit available)
•PVC coupling (or flange)
•PVC standpipe.
Figure 2 - Main Components of the Head Assembly
Head assembly sizes vary and are dependent upon the quantity and range of VW
displacement transducers. (See appendix A.4 Head Assembly for more information.) The
head assembly may be located above grade, recessed in a borehole, or seated in an
enlarged section of the borehole known as an overcore.
1.2.2 Coupling, Standpipe, and Flange
A standpipe is cemented into the bore hole and is connected to the head assembly either
with a PVC coupling or a set of PVC flanges. A custom bladder anchor can replace the
tube mount and standpipe. This is recommended for upward installations.
The head can be attached to the standpipe by gluing the PVC coupling on the head
assembly to a PVC standpipe inserted into the borehole. Two flanges can also be used
(glued to the head and the standpipe ahead of time) which are bolted together. The
standpipe and coupling, or flange/coupling assembly, are installed into the borehole. If

4
using a coupling, the standpipe and coupling would be cemented in place and left to set
up. With the standpipe secured in place, the MPBX string is lowered into the borehole
through the standpipe and then the tube mount is glued into the coupling or flange.
1.2.2.1 Inline Slip Couplings
The inline slip couplings are attached to individual rod columns by cementing the
coupling to the TUB-101 PVC pipe or using a barb fitting (on each end of the coupling)
to attach the coupling to the TUB-103 or TUB-109 ½-inch tubing. Both types are shown
below and come with a 10-cm or 30-cm range of motion. Multiple units in a single
column can be implemented if desired. The range of motion allows compression (or
extension) of the rod column in settlement (or heave) situations. Without the range of
motion, there might be substantial bending or breaking of the PVC tubing or coiling of
the rod column, which would introduce errors in the measured movement. They can be
set anywhere in their range and are shipped with dissolvable tape to wrap around the slip
location to temporarily hold it until the stainless steel or fiberglass rods can be locked.
They are usually installed just below the head assembly but can be placed anywhere
along the column. These couplings would be recommended where there is more than 1
inch of compressive movement. However, other considerations including grout stiffness,
hole diameter, and installation depth can influence decisions on the use of slip couplings.
Using a slip joint may also be considered where separation of the pipe or tube column
under significant extension situations would be undesirable.
Figure 3 - Slip Location for Inline Slip Couplings
1.2.3 Vibrating Wire Displacement Transducers
GEOKON Model 4450 Vibrating Wire Displacement Transducers consist of a vibrating
wire sensing element, in series with a heat treated, stress relieved spring. One end of the
spring is connected to a vibrating wire, the other end to the transducer shaft. Movement of
the anchors and attached connecting rods cause the spring inside the transducer to expand
or contract, which changes the tension in the vibrating wire. The change in tension
(strain) of the wire is directly proportional to the movement of the head relative to the
anchors or vice versa.
Slip Location