深中通道大节段钢箱梁卸船转存方案比选

Ship Unloading and Storage Transfer Scheme Selection for Large Steel Box Girder Segments of Shenzhen-Zhongshan Link

深中通道非通航孔桥有92片大节段钢箱梁需采用驳船运输到工地出海平台旁,卸船存放到平台上,再由中心起吊船“天一号”吊装、运输和架设。非通航孔桥每联首孔大节段钢箱梁长133.1 m,吊重1780 t。针对复杂海域环境下大节段钢箱梁的卸船转存施工,对侧滚拖拉滑移法和浮托法2种卸船转存方案从结构受力、施工难度、材料设备、安全风险等方面进行比选。结果表明:浮托法可利用现有出海平台,只需增建2组钢支墩和靠船系缆墩,以及2根钢托梁,利用潮汐水位变化和压舱水调节驳船干舷高度,充分发挥潮汐作用,降低海上风浪和潮汐流水环境中的侧滚风险,免去驳船左右舱调载工序,浮托钢箱梁卸船转存操作简单,每次浮托只需3~10 h,经综合比选后选择了浮托法。工程实践表明:浮托法解决了2万吨驳船调载慢的难题,加快了架设速度,确保了安全。

The non-navigation channel bridge of Shenzhen-Zhongshan Link consists of 92 large steel box girder segments that are required to be transported to the location besides the offshore construction platform at the bridge site by barges,unloaded off the barges,stored on the construction platform,and finally hoisted,delivered and erected by the floating crane“Tianyi”.The steel box girder in the first span of each continuous unit of the non-navigation channel bridge measures 133.1 m long and weighs 1780 t.To facilitate the unloading storage of the large steel box girder segments in harsh marine environment,two unloading and storing solutions,which were named side rolling,dragging and sliding method and float-over installation,respectively,were compared from aspects of load bearing behavior of the structure,construction challenges,Materials and equipment needed,and safety risk.It is shown that when using the float-over installation method,the uptake of the offshore construction platform is possible,adding merely two groups of steel supports,dolphins and two steel corbels will suffice to complete the task.The float-over installation method takes the advantage of the tidal variation and ballast water to adjust the freeboard height of the barge,where the function of tides can be used well,the lateral rolling risks in the marine waves and tides can be reduced.Furthermore,the balancing process of the left and right tanks of the barge can be skipped,the unloading and storage of the steel box girder segments is eased,and each operation can be finished within 3 to 10 hours.The float-over installation method is selected.The engineering practice proves that the application of the float-over installation method resolves the historical issue of slow load-balancing of the 20000 t-capacity barge,accelerates the installation speed and assures the construction safety.