TULIP Research Project (tunnel boring machines and limitation of impacts on piles)
In order to estimate the impact of the excavation process of the tunnel boring machine on deep foundations of nearby structures, the Société du Grand Paris (SGP) in partnership with the Graduate School of Civil, Environmental and Urban Engineering (ENTPE), the Center for Tunnel Studies (CETU) and the French Institute of Science and Technology for Transport, Development and Networks (IFSTTAR) have initiated the TULIP Research Project dedicated to this issue, through a full-scale experiment that was carried out in Aulnay-sous-Bois, on the line 16 of the Grand Paris Express.
This full-scale experiment includes:
- Construction of three piles with a diameter of 400mm, loaded with large steel piles of 240 tonnes each, to artificially recreate the weight of a building;
- Instrumentation and monitoring of displacement and stress fields in piles and soil before, during and after the TBM6 passage (Armelle tunnel boring machine).
Cementys provided instrumentation and monitoring of measurements on piles and in the field for the six-month period of this experiment (February to July).
This instrumentation includes:
Topographic measurements of XYZ displacements on the ground surface and at the top of the piles, with the following specifications:
- Two sections of reinforced measures (SMR North and SMR South) implemented in the direction transverse to the tunnel, with prisms as targets (Anti-vandalism prisms: PAV);
- Line of targets (Axis) implemented in the longitudinal direction of the tunnel, with VAPs as targets;
- Optical Mini-Prisms (MPO) implemented on either side at the head of each pile;
- All of these targets (around 80 targets) are tracked by using three automatic theodolites.
Monitoring of lateral displacements of soil from the surface through the installation of bidirectional inclinometers in borehole with the following specifications:
- Four vertical inclinometer chains with a depth of about 30m each and one vertical inclinometer chain about 15m deep, implemented on the North and South SMRs;
- The measuring directions of the inclinometers correspond directly to the longitudinal and transverse directions of the tunnel.
Monitoring of soil movement from the surface through the installation of multi-point extensometers in boreholes with the following specifications:
- Four 30m deep vertical extensometers (one measurement every 3m over the entire height of the 9-point extensometer) and one 15m deep vertical extensometer (one measurement every 3m over the entire height of the extensometer with 5 anchoring points) implemented on the North and South SMRs.
Monitoring of pore pressures in of soil from the surface through the placement of sacrificial pore pressure cells (IPCs).
The measurements were carried out with the following frequencies:
- One measurement every 4 hours before the passage of the TBM6 under the experimental site;
- One measurement every 30 minutes during the passage of the TBM6 under the experimental site;
- One measurement per hour after the passage of the TBM6 under the experimental site.