ABSTRACT
The life cycle of TBM segments of a new tunnel were assessed considering two main degradations for the side exposed to ambient air and for the side exposed to the ground. The two degradations were carbonation attack and sulfate attack, respectively. In order to numerically model these two degradations, Full-Probabilistic Approach (FPA) was employed, using fib34 and FEM model, respectively. To calibrate the model for the carbonation simulation, inverse carbonation resistance https://www.w3.org/1998/Math/MathML"> R a c c , 0 − 1 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003323020/12afb023-302c-4972-8445-2baf499347cb/content/inline-math426_1.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> of the concrete mix (40% slag, w/c=0.35, cement = 467 kg/m3) used for TBM segments, was examined in the laboratory. The relative humidity values were also acquired from the nearest weather station in the area. To calibrate the FEM model for the sulfate attack, the chemical composition of the ground and groundwater was acquired from the nearest geological boreholes. The results showed that the carbonation penetration after 100 years of service life in term of 95th percentiles of normal distribution is 14 mm. The carbonation penetration depth in comparison to 50mm concrete cover of the TBM segment does not seem to be problematic and results in <0.1% failure probability. Moreover, thickness loss due to decalcification of CSH by sulfate attack in terms of 95th percentiles of normal distribution is 7.22mm. The thickness loss does not seem to be problematic for the extrados of the TBM segments, comparing to the 50mm concrete cover and to 14.5mm depth of embedded anchor of sealing gaskets. The findings imply that the sulfate attack does not result in loosening of the sealing gasket.
