Bertha, the 57.5-ft-dia tunnel-boring machine attempting to dig a 1.7-mile state Route 99 tunnel underneath Seattle, is stuck again, having progressed 4 ft after a delay in December. Now, Seattle Tunnel Partners (STP), a joint venture of Dragados USA and Tutor Perini Corp., have decided to build a shaft in order to reach the TBM after discovering the 35-ft-dia seals surrounding the main bearing are broken.

STP and Hitachi Zosen, the Japanese manufacturer of the $80-million, 7,000-ton, 300-ft-long machine, already have started on the plan to build a 120-ft-deep, 80-ft-wide shaft in order to reach the cutter head's face 50 ft below the surface. The plan is to access Bertha from the front, instead of through the 1,023 ft already tunneled to its back end.

"If [you enter] from the tunnel on the backside of the cutter head, access is difficult. It is a cramped environment," says Chris Dixon, STP project director. "If you go down from the surface, you have more room to work, less things to remove to get out of your way and a free-air environment, so people can work regular shifts with much more efficiency."

STP和华盛顿州运输部都表示，没有时间表到到达刀头，进行密封维修并让Bertha再次移动需要多长时间，但Dixon承认“它将花费几个月”，保证延迟延迟到达31亿美元的阿拉斯加道高架桥更换项目。

在高温和缺乏进度的情况下，伯莎（Bertha）于2013年12月6日首次关闭，警告了操作员解决问题。官员们认为障碍物，例如冰川巨石，造成了阻塞。该机器的性能比预期的要好，每天前进30英尺。

钻孔的测试轴和158小时的高压检查发现没有阻塞，尽管切割机的工具被损坏并堵塞了污垢。STP和WSDOT在检查期间发现了一个8英寸的钢铁井外壳。STP说，套管阻止了伯莎，但WSDOT不同意。

由于内部机器温度读数为140°F，超过正常水平的1.5倍，因此工作人员试图在1月28日再次移动Bertha，但在1月29日将她关闭了4英尺。

进一步的调查发现，主要轴承密封损坏，尽管STP说主要轴承没有损坏。由于破损的主轴承在TBM上并不少见，因此设计构建合同规定第二个主轴承必须坐在准备就绪。Bertha的设计使得，在项目期间的任何时候，可以从隧道内和背部更换主轴承。

WSDOT的Alaskan Way替换计划管理员Todd Trepanier说，由总部位于德国的Rothe Erde制造的500万美元可以到达必要的安装。但是目前，计划是更换橡胶密封件，以确保油脂限制机器内部的摩擦和加热。迪克森说，在伯莎再次移动之前，主要轴承将得到重新认证。

Dixon says STP does not take "final acceptance" of the machine until 200 concrete liner rings are placed, so after 150 rings, Bertha is still under warranty from Hitachi Zosen. The final 10% payment to Hitachi isn't due until final acceptance.