Septum 16 shielding increase

L.A. Lopez Hernandez

Septum 16 shielding increase

19 November 2013

Requested: - Additionnal depth of earth of between 1.2m and 3.4m over Septum 16 area

Constraints: - Existing structures not strong enough to take the additional load- Area with a very complex geometry (PS, Linac 2&3, Leir, TT2, . .) - Works must have no influence or impact on the existing structures

Proposed solution : -A new load-bearing structure taking the weight of the additional earth and redirecting it into the bedrock underneath.

-The structure consists of a 1.10 m thick reinforced concrete slab and the additional depth of backfill will be placed directly on the slab.

-The slab rests on drilled piles and on intermittent supports on the tunnel roof

Slab deformation:

51 mm

56 mm

- To protect the existing structures, the transfer slab must guarantee that even after long-term deformation the load-bearing relief structure does not under any circumstances come to rest on the existing structures.

- To this end, it was foreseen to use a biodegradable honeycomb cardboard formwork that could be be dissolved with water. This procedure guaranteed that, once water had been injected to dissolve the cardboard, a void of 10 cm remained after concreting, which was more than enough to allow for the long-term deformation of the slab

Status – 19 November 2013

• Adjudication of the works on 19 June 2013 • June-July 2013 - Preparatory works • July 2013 – Earthworks • September 2013 - Piling works • 2 October 2013 – Start of concreting works – Stage 1a• 8 October 2013 – Works stoppage – The biodegradable

formwork gets wet before concreting !• 8-16 October 2013 – Removal of the formwork&reinforcement of

stages 1b and 2a • 18 October 2013 - a new method is developed and tested:

sand instead of biodegradable formwork, to be pumped out prior to backfilling

• Now – Stages 1b and 2a concreted using the new method

Some pictures of the works:

Earthworks - July 2013 Piling works – September 2013

Concreting works with biocofra – October 2013

Demolition works – 8-16 October 2013

New concreting operations with sand – November 2013

New schedule

End of the works:

15/03/2013 (to be

confirmed depending on the speed in pumping the

sand)

Thank you for your attention