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Hyperbaric Tunneling

Tunnelbau

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The Nanjing Yangtze River Crossing Tunnel

The Nanjing Yangtze River Crossing Tunnel is a 2.990 m long twin tube crosses the river Yangtze in Nanjing, China. Two Slurry-TBMs (Ø 14.96 m) are in use to excavate the tunnel in soft alluvium strata. The strata are mainly silt and fine sand.

The tunnel invert’s deepest point is 65 m below sea level.Due to tidal influence the water level of the river is typically between +/-1.5 m above/below sea level.

On this project, welding in compressed air was the major task to carry out. From our experience and research of welding in compressed air and under water we knew that it is not a real problem. But this time it was very extreme. The buckets of 6 arms of the TBM had to be renewed. Therefore we welded new supports on the side arms of the cutterhead. The total time of this work took more than 12 weeks, day and night. The pressure was up to 5.4 bar overpressure in air. To keep the support pressure stable we used bentonite with a special mixture of high density and viscosity.

Maintenance and repair under compressed air was performed at up to 5.4 bar air pressure for works at the cutterhead and up to 6.5 bar for works at the stone crusher. Regular compressed air (no mixed gases) and oxygen decompression is successfully in use. In total more than 4.000 h of compressed air works and more than 945 total man interventions are performed. Only 3 minor cases of decompression illness are reported.

For the welding operation we used the first time a new special designed compressed air helmet with triple air supply, two regulators and one free flow, communication and an integrated welding shield with sensors.

The Nanjing Yangtze River Crossing Tunnel

中国南京长江隧道是在中国南京的穿越长江的隧道项目,为全长2990米的双隧道,使用的是两台直径为14.96米的泥水盾构,掘进地质为黏土和细沙组成的软冲积层。

隧道仰供块最深处低于海平面65米,由于潮汐影响,河面水位在正负海平面1.5米范围内波动。

此项目的主要施工任务为压缩气体内进行焊接作业。根据我们以往的研究与经验,在压缩气体内进行焊接作业并不成问题。但由于此次刀盘六个刀臂的铲刀均需翻新,所以任务十分艰巨。在焊接进行前,刀盘边侧需焊接支撑。为此,我们全天候日夜连续工作了12周。工作压力已经达到5.4巴,为稳定压力,我们选用了添加了高密度、高黏稠度的混合物的膨润土

焊接工作中,我们采用了最新设计的面罩。面罩配有三条供气管路,2个调节器、1条自由管路、通讯线路和带传感器的焊接护罩。
刀盘维修作业的压力最高达到5.4巴,碎石机维修作业压力最高至6.5巴,但普通压缩空气作业(非混合气体)以及含氧减压都顺利进行。在总共4000小时的待压作业中,共进行了850人次进仓作业,减压病报告仅为3例。

在舱内焊接时,我们也首次使用了特制的焊接头盔。头盔中配置了三套空气供给管路(两套可调节、一套自由流通),通讯线路和内置传感器的焊接面罩。