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The construction of the new Lyon-Turin HS Base tunnel consists of 57km of twin tunnels under the Alps which is the longest tunnel ever excavated. SYSTRA is a part of the JV in charge of the tender and final design as well as site supervision of the central section of this tunnel. Such a mega-project must deal with various typical technological and constructional challenges of the long and deep tunnels. According to the tunnel depth and complex geological context, risks of severe squeezing, rockburst, fault zones and high-water inflows are awaited. In order to handle all these challenges, SYSTRA performed a complete Risk Management Plan, the final design has been focused on the Risk-driven approach consisting in the identification and mitigation of the related risks by the tunnel design itself including the excavation methods, the tunnel section type and the proper choice of supports and installations. In order to manage the residual risks, a special monitoring and a countermeasures approach have been also anticipated from design stage. The output in a risk matrix form is now applicable during the tunnel construction phase. This paper discusses the risks, the technical solutions and the resulting design efficiency. [ABSTRACT FROM AUTHOR]