With 2330m length and 180m2 crosssection area, Tartaiguille tunnel runs through fractured soft ground. The tunnel is originally excavated by top heading/bench method and is reinforced with shotcreting, rock bolting, steel ribs and castinsitu concrete lining. During the construction of the tunnel, serious deformation occurs so that the construction of the tunnel has to be suspended. New design and construction solutions must be adopted for the tunnel. After full examination, ADECORS approach is finally adopted for the design and construction of the tunnel and great success has been achieved. Case study is made on the application of ADECORS approach in the design and construction of the tunnel in respects of survey stage, diagnosis stage, therapy stage, operation stage and operation stage.