LUCOEX / Work Package 3

ALC Full scale emplacement experiment at Bure

Task 3.1 Detailed design of the experiment including an in situ test of forced casing digging to prepare the digging of the cell

The design of the ALC experiment is supported by Thermo Mechanical modelling (not included in the project) and preliminary in situ test. One of the key issues of demonstration of cell within the French concept is feasibility of the cell’s head, which is a casing emplaced with the minimum void in between the casing and the rock walls. The casing is 10 m long and will be forced in the micro-tunnel to minimize the void around the casing. Such operation has never been performed in the Callovo-Oxfordian claystone at the Meuse Haute Marne Underground Research Laboratory.

A first in situ test to emplace a forced casing (consisting in five 2 m long metal tubes, diameter 775 mm) with a void of 16 mm over the diameter will be performed at the beginning of the project to check the feasibility with the actual digging machine and to improve it, if necessary. The axial load on the casing will be recorded during the test.

The experimental test plan will be written and will describe the objective of the demonstration experiment, the geometry of the experiment, the procedure of emplacement and the prescribed heating phase.

Task 3.2 Emplacement of the cell

The purpose of this task is to validate the emplacement procedure. That means:

  • forcing the head insert (10 m long) into the drift wall
  • digging of the microtunnel of 25 m long with simultaneous emplacement of a steel casing
  • installing the end steel plug
  • introducing the heaters and the shield steel plug

The digging of the cell will be performed with a guided auger drilling machine. The drilling head can be adapted to excavate in diameter 70 to 74 cm. It allows also the retraction of the drilling machine at the end of the excavation, by rotating in the opposite direction as for the excavation. The drilling machine is laser guided, what allows the control of the micro-tunnel trajectory with a precision better than +/- 2 cm. The digging will be achieved with casing. The casing is made of 2 m long, 70 cm in diameter and 2 cm thick metal tubes. The drilling is carried out with air. The casing of the cell will be instrumented to provide data on the casing behaviour under a thermal loading. The heaters will be installed in the cell’s casing between 10 m to 25 m in depth. A shield plug will be put into the casing just at the end of the insert.

In addition, boreholes will be performed to set up instrumentation around the cell in order to analyse the working of the head concept under a thermal loading: temperature (2 boreholes) to measure the thermal gradient to the drift. The relative displacement of cell casing to the insert will be measured to check the running of the head with the dilatancy. Deformations of the drift at the cell head will be also followed to verify the design of the cell head in order to check stress and deformation induced by the thermal gradient.

Task 3.3 Final reporting of WP 3

This task addresses the compilation of all WP 3 results in a final WP report, and present mainly:

(a) an analysis on the emplacement phase (head insert, digging of the micro tunnel and casing)

(b) an analysis of working of the head during the heating phase in order to verify the suitability of the head insert to absorb the thermal dilation of the casing. That means an analysis of: the casing deformation, the relative displacement in between the casing and the insert and the thermal gradient around the head.

Task 3.4 Integration

This task is linked with WP1 in order to increase integration and good practices between the project partners.

Subtask 3.4.1: Small workshop in conjunction with Project Progress Meetings of WP3

Project Progress Meetings are planned to be held with approximately 9 months intervals. At the meetings, taking place after approximately 18 and 36 months from project start, small workshops are planned to be held with an extension of approximately half a day.

The presentations are planned to be directed toward the other participants in the LUCOEX project for sharing information and discussing technical issues. They are also foreseen to be open to invited scientists and engineers important for respective participant’s programme.

These workshops are documented in respective periodic report (WP1) and in summary on the public part of the Web portal including public material like PP-presentations and posters if presented.

These Project Progress Meetings and workshop are intended to be held in France at Bure or Chatenay-Malabry.

Subtask 3.4.2 Active exchange of experiences

The task addresses the following activities:

  • Invitations to the other participants to participate to Project Progress Meeting (1 every 9 months), to attend installations and demonstrations (during insert test (month 2) and during emplacement of the cell (≈month 12-16) with the aim to give input to the WP
  • Networking for new scientists
  • Expert advice of other participants on the WP test plan
  • Review of the WP final report by the other participants to verify relevant information for the project is all in. For this review a group of experts could be formed with internal and external experts (like experts from the panel of technical expert (WP1) or others). The mean of this review is to serve as means for critical cross examination, assessment, integrated analysis of the results and achievements (in terms of feasibility of the emplacement concept and working during the heating phase), in order to prepare conclusions for the task 1.11

  • Localization: France
  • Facility Bure URL
  • WP-manager: Jacques Morel