Taxaquara fault – A complete solution for a complex problem

São Paulo Line 6 is currently one of the most challenging projects worldwide. A design and build megaproject integrating the simultaneous construction of more than 15 km of TBM tunnel, 15 stations, 17 shafts and around 2km of non-mechanized tunnels. The main tunnel is divided in two streches, to be bored by two EPB-TBMs (10.61m OD) starting from the same shaft – VSE Tiete. The north run starts right in the transition between sedimentary soil and hard granite, with a 40m long parallel fault to the tunnel drive – Taxaquara Fault. A complete risk analysis of the construction methodoloy was performed, consubstantiated in a special geotechnical and hydrogeological survey, which concluded that the best solution would be the combination of twin shafts with a series of sprayed concrete lining (SCL) tunnels with external and internal dewatering. This paper describes the risk assessment, design, and construction phase necessary to successfully complete this challenge.