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Real-time modelling and compensation of soil movements on underground sites

Objective


1. Recommendations for the analysis of drilling parameters recordings
2. 3D numerical model for the simulation of compensation grouting sites
3. Methods for the modelling of grouting
4. Methods for the modelling of shield tunnel
5. Software for the control of grouting on compensation grouting sites
6. Software for real-time monitoring of movements and internet communications.
7. Real-Time Observational Compensation Grouting process (OCG), including a real-time feedback between grouting operations and numerical simulations.
8. One prototype of fibre bragg-grating (FBG) industrial logging unit.
9. Prototypes of FBG strain sensors.
10. Prototypes of FBG inclinometers.
11. Prototypes of piezo-electric stretchers for fibre optics.
The construction of underground transports, particularly
in urban areas, is a potential source of major damages to
existing buildings and structures: soil movements caused
by underground excavations always propagate to the
surface, causing cracks and fissures to old buildings. In
order to face the growing need for underground transports
in overcrowded towns, it is necessary to develop a method
able to compensate for soil movements due to underground
excavations and to reduce significantly the social risks
accompanying these construction sites.

A new method, the ' Compensation Grouting ', is proposed
to assess and control the produced movements of existing
structures, with the objective to compensate
soil/structures movements and keep their variations
within +/ lmm. This method consists into
I) creating a 2D or 3D model of the site to predict soil
movements and design the compensation;
2) grouting into the soil a self hardening slurry when
the tunnels are excavated, under a constant and automated
control of grouting pumps, and a real time monitoring of
soils/structures movements;
3) continuously update the 3D model from observed
movements and from grouting results.

The project involves on one hand the development of 2D
and 3D modelling methods to characterise the soils, to
predict the effects of the excavations and to design the
required compensation grouting, and to compare every day
the observed measurements with expected results, in order
to adjust the model to reality. On the other hand, an
instrumentation and control system must be developed to
control the grouting plant with a high precision while
monitoring soil/structure displacements in real time,
with the objective to map displacements and to control
grouting operations every 30 seconds.

The accuracy of sensors currently used in civil
engineering sites is too poor to reach the objective;
moreover their thermal sensitivity is high and difficult
to compensate. New sensors have to be designed according
to user ' s specifications (cost, difficult environment,
and temperature variations). Therefore the project
includes the development of a fibre optics sensor
network, with a low cost and ruggedized demultiplexing
unit, and two new fibre optics sensors:
strain/displacement sensors to obtain a precision of 10
mm/m on vertical movements, and tiltmeters with a
precision of 0.05 mm/m (i.e. 10 seconds of arc).

The Consortium comprises two industrial end users: a
consulting engineer, specialised in the fields of
geotechnique and transport facilities development, and a
contractor specialised in grouting and foundations works.
It also comprises an industrial manufacturer and a
research organisation specialised in the field of fibre
optic sensors and networking. Two partners from
Universities will bring expertise on soil mechanics and
soil modelling, and on advanced ceramics materials for
the fibre optic network.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Soletanche Entreprise SA
Address
6 Rue De Watford
92000 Nanterre
France

Participants (5)

Commissariat à l'Energie Atomique
France
Address
Ctr Etudes De Saclay - Ce-s
91191 Gif-sur-yvette
GLOETZL, GESELLSCHAFT FUER BAUMESSTECHNIK MBH
Germany
Address
Forlenweg 11
76287 Rheinstetten
SWISS FEDERAL INSTITUTE OF TECHNOLOGY LAUSANNE
Switzerland
Address
Mx-g Ecublens
1015 Lausanne
Tractebel Development SA
Belgium
Address
7,Avenue Ariane
1200 Bruxelles
University of Cambridge
United Kingdom
Address
Trumpington Street
CB2 1PZ Cambridge