Limerick tunnel project
Customer
Capita Symonds Ltd. is the Designer for the National Roads Authority and Direct Route Limited. Direct Route Limited has designed and constructed the Limerick Scheme Tunnel. They will also operate and maintain the tunnel. Capita Symonds Limited asked SGS INTRON to provide specialists services for the Limerick tunnel project. SGS INTRON was asked to act as a specialist consultant to Capita Symonds in the field of prevention of early age thermal cracking.
Case
The Limerick Tunnel is situated west of the city Limerick. The length of the immersed tunnel is 500 m The total length with approach ramps and the cut-and-cover tunnels is 915 m. The tunnel is facilitated with a two-way traffic system with four lanes. The cross section of the tunnel is 25250 mm wide and 8450 mm high. The cross section contains two road sections.
A tunnel with these dimensions and situated in this environment has high risk of cracking due to temperature development during the hardening of the concrete.
Aim of the study was to give recommendations to reduce the risk of early age cracking in the precast tunnel elements of the Limerick immersed tunnel.
Solution
SGS INTRON is world leading in this field of expertise. For the Limerick project they provided the following services:
- Specification for the pre-testing of the concrete
- Specification of the full scale testing
- Review of proposed mix design
- Review of the pre-testing
- Review and supervision full scale testing
- Development of measures to reduce risk of early age cracking
- Review of work method statements.
SGS INTRON is very experienced in designing concrete mixes suitable to prevent early age thermal cracking and complying to specifications regarding durability and strength. SGS INTRON has commented on the proposed mix designs in relation to the expected behaviour of the hardening concrete.
SGS INTRON has reviewed and supervised highly specialized concrete testing like adiabatic heat development, early age creep and autogenously shrinkage.
For the development of the risk reducing measurements SGS INTRON used the finite element tool HEAT of FEMMASSE for the Limerick project. It is a highly specialized tool that was used for many projects amongst which the Øresund project and the Marmaray project.
With the designed measures and prescribed procedures again it proved possible to construct a tunnel like this without cracks. Of all the elements produced only one element showed unexpected cracking. This was for the first element after reviewing the methods and results, all other elements were cast without cracks.
Year
2006-2007