Geosense GXM-300 Series User manual

V1.4 July 2020
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GXM-300 SERIES
MAGNETIC SETTLEMENT SYSTEM

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CONTENTS
Page
1.0 INTRODUCTION 4
1.1 General Description 4
1.2 Theory of operation 5
1.3 Components 6
2.0 DELIVERY 7
2.1 Packaging 7
2.2 Handling 7
2.3 Inspection 7
2.4 Storage 7
3.0 INSTALLATION 10
3.1 BASE Readings 10
3.2 Getting Started 11
3.3 Installation - GXM300 12-18
3.4 Installation - GXM300I
4.0 DATA 19
4.1 Taking Readings 19
4.2 Data Reduction 20-21
5.0 GROUTING 22
6.0 MAINTENANCE 23
7.0 TROUBLESHOOTING 23
8.0 SPECIFICATION 24
9.0 SPARE PARTS 25
10.0 RETURN OF GOODS 26
11.0 LIMITED WARRANTY 27

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It is VITAL that personnel responsible for the
installation and use of the GXM-300 Series READ and
UNDERSTAND the manual, prior to working with the
equipment.
1.1 General Description
The GXM-300 Series, is a magnetic extensometer that is installed into fills or unstable
ground, to monitor settlement or heave, that may have occurred due to different civil/
geotechnical engineering activates, such as:
• Embankment Construction
• Earth Dam Construction
Data obtained form this type of instrument will highlight the settlement or heave
occurring in the ground, as well as highlighting the zones in which the highest
settlement / heave is occurring. This aids in the design of structures, when construction
is undertaken.
The primary use for the GXM-300 Series is :-
Soil settlement measurement.
Particular features of the Geosense GXM-300 Series are:-
Reliable long term performance.
Rugged; suitable for demanding environments.
The magnetic signals are particularly suited for the demanding environment found in
civil and geotechnical engineering industries.
The Geosense range of GXM-300 Series can be supplied in various configurations to
suit varying installation environments and techniques.
1.0 INTRODUCTION
This manual is intended for all users of the GXM-300 Series manufactured by Geosense
and provides information on their installation, operation and maintenance.

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1.2 Theory of Operation
The GXM300 Series magnetic extensometers
is installed in embankment fills or boreholes
that are associated with different civil /
geotechnical engineering applications. The
GXM300 Series magnetic extensometers
come in two different forms, as follows:-
Magnetic Settlement Systems GXM300.
This magnet settlement system incorporates
access tubing and corrugated piping. This
corrugated piping is placed over the access
casing in sections. These corrugated piping
sections are then linked together with couplers
or magnetic couplers. The corrugated piping is
not attached to the access casing, so allowing
the corrugated piping to movement with the
ground as it settles or heaves.
Magnetic Settlement Systems GXM300i
This system operates and is installed, in the
same manner as the GXM300. The only
difference between the GXM300 and GXM300i
is that the GXM300i incorporates inclinometer
casing into its installation.
Operation
The system comprises of a reed switch probe,
a steel measuring tape, a tape reel with built-in
buzzer and a series of magnetic targets located
along the length of a access tube. As the probe
passes through a magnetic field the internal
reed switch closes, activating the audible
buzzer and light, so that the location of the
magnetic target can be identified by measuring
to the nearest millimetre on the graduated tape.

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1.3 Components
Access Tubing (GXM-300) : Allows the reed switch probe to be lowered so measurements
of the magnetic target position can be taken.
Inclinometer Casing (GXM-300I) : The casing allows the reed switch probe to be lowered
so measurements of the magnetic target position can be taken. This casing also allows
inclinometer probes to be inserted into the casing so lateral movements can be monitored.
Corrugated Piping: This piping is placed over the access tubing in sections. These
corrugated piping sections are then attached together, with couplers or magnetic couplers,
which are attached to the corrugated piping with screws. This casing is intended to de-bond
the access tubing from the surrounding soil and move with the fill as it settles or heaves.
Couplers: These couplers are fixed to the corrugated pipe section in order to extend the
section of corrugated piping to the elevation required to install the next magnetic couplers.
Magnetic Couplers: These are the magnetic targets that are used to trigger the reed switch
probe. These are attached to the moving corrugated piping with screws. These can be
positioned at different locations along that installation.
Datum Magnets: All readings made are taken in reference to the datum magnet, which is
fixed in place on to the access tubing, is none moveable and located in stable ground.

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2.3 Inspection
It is important to check all the equipment in the shipment as soon as possible after
taking delivery and well before installation is to be carried out. Check that all the
components detailed on the documents are included in the shipment. Check that the
equipment has not been physically damaged.
2.0 DELIVERY
This section should be read by all users of GXM-300 Series manufactured by
Geosense.
2.2 Handling
Whilst they are a robust devices, GXM-300 Series are precision measuring
instruments. They and their associated equipment should always be handled with
care during transportation, storage and installation.
Once the shipment has been inspected, it is recommended that GXM-300 Series
remain in their original packaging for storage or transportation.
2.1 Packaging
GXM-300 Series are packed for transportation to site. Packaging is suitably robust to
allow normal handling by transportation companies. Inappropriate handling
techniques may cause damage to the packaging and the enclosed equipment. The
packaging should be carefully inspected upon delivery and any damage MUST be
reported to both the transportation company and Geosense.
2.4 Storage
All equipment should be stored in an environment that is protected from direct
sunlight.
No other special requirements are needed for medium or long-term storage.

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It is VITAL that personnel responsible for the installation and
use of the GXM-300 Series READ and UNDERSTAND the
manual, prior to working with the equipment.
**********
As stated before, it is vital to check all the equipment in the
shipment soon after taking delivery and well before installation is to be carried out.
Check that all components that are detailed on the shipping documents are
3.0 INSTALLATION
This section of the manual is intended for all users of GXM-300 Series manufactured
by Geosense and is intended to provide guidance with respect to their installation.
It must be remembered that no two installations will be the same and it is inevitable
that some ‘fine tuning’ of the following procedures will be required to suit specific site
conditions.
3.1 BASE Readings
IT IS ESSENTIAL TO TAKE BASE READINGS OF THE DATUM
MAGNET WHEN INSTALLATION IS COMPLETE.
IT IS ALSO RECOMMENDED TO TAKE THREE SETS OF
READINGS FROM DIFFERENT PASSES THROUGH THE ACCESS TUBING AND
AVERAGE FOR EACH MAGNETIC TARGET.

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3.2 Getting started
Ensure that all the equipment needed is laid out on clean ground and the number of
items needed for installation are checked. Check that all equipment provided is not
damaged and is clean.
Prior to installation of the GXM-300 it is essential to confirm details of the installation to
be carried out. Some of the main considerations are listed below :-
1. Number of installation, datum magnet and magnetic targets.
2. Borehole Identification.
Boreholes that require the GXM-300 Series to be installed in them should be
clearly identified and a labelling/ marking scheme should be established with the
client before installation is under taken.
3. Tools.
Obtain any tools necessary to carry out the installation. The following is a brief list
of tools typically used during the installation of GXM-300 Series
• Tape Measure
• Cleaning Solvent
• Adhesive
• Star Screw Driver
• Permanent Maker Pen
• Allen Key
• Duct Tape
4. Extensometer Components.
•Access Tubing
• Corrugated Piping
• Couplers
• Magnetic Couplers
•Datum Magnet

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3.3 Installation Procedures - GXM300I
1. Check the drill hole to ensure that the full depth is
clear and free of obstructions. Ensure that the
base of the borehole is in solid ground.
2. Lay out all the equipment that is supplied,
ensuring that the quantity is correct for the
installation.
3. Snap the end cap to the casing.
4. Insert the casing into the corrugated piping.
Ensure the corrugated piping is taken above the
end of the access tubing.
5. Place the datum magnet onto the end cap at the
bottom of the access tube.