Trade Journals for the Concrete Industry

Nowadays, tunnels are often excavated using tunnel boring machine (TBM). The lining of such tunnels is a succession of rings generally made of precast concrete segments. The concrete segment industry needs very stiff moulds with very accurate geometry to support high vibration energy applied on the mould a thousand times during its lifetime and to achieve segments perfect enough to provide water tightness, to support ground loads and to withstand the huge TBM thrust jacks once assembled. Moreover, segments production is a tough task for operators especially due to the noise pollution of the external vibrators and the finishing of the extrados. A new and innovative method was developed to reduce the premature ageing of the moulds, to minimize as far as possible operators tough tasks and to produce easily top quality segment with an extrados side achieving and even exceeding geometrical tolerance and smoothness requirements. This paper explains the interest in the proposed method which combines the use of Self Compacting Concrete (SCC) with an inventive segment mould and then describes the real scale test results.