Abstract
The Mantanza-Riachuelo basin recovery is one of the most ambitious environmental projects under construction in Argentina. In this context, the sanitary bureau of the metropolitan area of Buenos Aires (AySA) is building a sewage collection network to transport the waste water of the population in the southern area of the city, composed by almost five million people. The most complex tunnel in this big project is named Lot 3, an outfall EPB-TBM tunnel starting at a deep shaft 40 m located at the Rio de la Plata margin and running under the river 12 km to a discharge area.
The tunnel runs through soft clay belonging to the post-pampeano formation, and dense sands of the Puelchese formation. In operation, it will be pressurized by a pumping station which will produce a piezometer head that, in the first 2000 m, might be eventually higher than the confining pressure around the tunnel.
This paper presents the numerical analysis of the structural forces acting on the tunnel rings using a risk oriented approach that considers the stochastic nature of materials, startigraphy and tunnel-ground interaction.
The compression of the tunnel segmental lining is evaluated and compared with field measurements in order to predict the structural forces and the risk of the rings going into tension beyond the structural capacity of the system.
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