Page 7 - Deformation Monitoring

www.moniterra.engineering DEFORMATION MONITORING

3. CONVECTIONAL THREE-DIMENSIONAL arbitrary time and the maximum measurement range is in
TOPOGRAPHICAL MEASURING SYSTEMS accordance with the environmental conditions.

Three dimensional displacement measurements (3D) will be The accuracy of the measurements from one installation point
carried out to determine the movement of the linings in the fulfils the following requirements:
conventionally constructed tunnel and cavern works or to • Plus/minus 1 mm in the vertical plane
determine the complete movement of buildings (in this case
the 3D optical targets will be installed in the upper part of • Plus/minus 1 mm in the horizontal plane
buildings). Reflectors are installed in tunnels, structures etc. and The overall accuracy of a network of robotic total stations
the measurements are made with high precision total stations covering an area of the works in relation to the fixed points
by the method of free station. The reflectors are standardized, outside the area of influence of the works is as follows:
made by an approved manufacturer, allowing precision of
measurements of +1 mm in each of the three directions and • Plus/minus 1 mm in the vertical plane
will be of bi-reflect target type or prism-target type. • Plus/minus 5 mm in the horizontal plane
For the monitoring of the permanent lining of tunnels and The installed system is capable of absolute measuring of any
stations, only prism-target reflectors shall be used. The total prism position within the above accuracies of the project grid
stations that are used have minimum precision of +1’’ for as a vector of combined X, Y, and Z movement when the
angles and ±2 mm+2 ppm for distances. barometric and temperature corrections have been applied.

The reference plan view network of the points, which is to be The total stations are remotely controlled by software and are
used for 3D measurements results from the thickening of the capable of:
base or even the secondary plan view network, consists of at
least six (6) reference points with permanent labelling at locations • Following a pre-programmed operation
outside the zone of influence of the works (for the surface • Allowing changes in the measurement regime to be
measurements in three dimensions) or at locations remote to implemented, including the measurement cycle
the excavation faces (for the underground measurements). The
reference network will be checked at regular time intervals (of • Providing continuous data for one point
at least three weeks). All the measurements are corrected by The system allows the above changes to be made remotely
the impact of the pressure and temperature diffractions. The via modems and telecommunication lines. The instruments are
precision of the measurements of total displacements (3D) is capable of self-seeking a point which has moved by at least 30
±2 mm. mm, without affecting the monitoring regime/data return time
The measurement readings are electronically recorded and adversely.
automatically transferred to a processing and entry program The instruments are generally located within the predicted zone
in the MDB. of influence and therefore cannot be fixed absolutely in space.
The measurement processing software is available to the In order to provide the absolute values required for the position
Client. of each prism, it is necessary to tie the instruments back to
fixed points outside the zone of influence from the works. The
4. AUTOMATED MONITORING SYSTEM (AMS) OF network of prisms, therefore, is established so that a proportion
REAL TIME TOTAL DISPLACEMENTS (3D) of the prisms is outside the zone of influence and a proportion

Moniterra will design and install an automated measuring of the prisms (control stations) is shared between adjacent
system for the total displacements (3D) in real time in zones instruments.
where the TBM tunnelling or other tunnel/station/shaft works The locations of the instruments, fixed points and Control
might give rise to settlements to sensitive buildings and other Stations are established so that a robust and rigid monitoring
structures. network is set up.
The system consists of a series of networked robotic total The data collected are processed in TCB Software Package .
stations and prisms located along the Project’s alignment.
Moniterra determines the detailed programme for automated Moniterra possesses an available number of instruments
monitoring within the general requirements given below. needed for covering in full the monitoring of any work and
wherever else required without measuring gaps and taking into
This system ensures valuable and timely monitoring of consideration the progress works. An adequate number of
the displacements, providing high measurements density, spare instruments is available to Moniterra.
simultaneous wireless transmission and entry of the results into
the MDB system to ensure minimal time between their reading The minimum requirements for the installation of reflecting
and their evaluation. prisms follows the relative design study.
The measurements are taken with a series of automatic When an automated monitoring is foreseen, a minimum
electronic total stations of high precision, which will record the number of levelling points for manual readings are installed
displacement of reflecting prisms on the ground surface and and read at daily frequency in order to calibrate the automatic
on buildings. system and
The robotic total stations are capable of carrying out automatic to have a network of control points on which to rely in case of
measurements, both at predetermined sequences and at any damage or temporary unavailability of the automatic system.

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