Abstract: An ultralarge diameter slurry shield, called Shenlan, was applied in the TJ06 bid section of the Jiaozhou Bay second submarine tunnel in Qingdao, China. When this shield crossed the uppersoft and lowerhard composite strata, fullsection tuff, fault fracture zones, and fullsection granite for a long distance with high water pressure, several problems, such as cutter wearing, inadequate rockbreaking capacity of cutter, stagnant discharge of the slurry chamber, muck cake on cutterhead, and failure of the shield tail and the main drive, were encountered. Thus, targeted designs are conducted as follows: reducing cutter space, optimizing cutter arrangement and form, using slag discharge mode by largediameter short spiral followed by a jaw crusher, and strengthening and optimizing the scouring system of the cutter blade and the slurry chamber. The applicable findings of these designs result in the reduction of energy consumption and cutter damage, relief of stagnant discharge in the slurry chamber, and better construction efficiency, thereby ensuring enhanced construction safety.

Key words: submarine tunnel, ultralargediameter slurry shield, shield selection, targeted design, fault fracture zone, fullsection hard rock