(央视超级工程记录片解说词摘要)现在,长江上第163座大桥正在开工——杨泗港大桥。它建成后将成为世界上跨度最大的双层公路悬索桥。在这条世界第三大河流上修建桥梁,现在要面对的最大的困难和60年前一样,都是“如何在河床上修建桥墩”。经过数千年的冲刷和沉淀,长江下游几乎找不到坚硬的河床基础,于是工程师们采用一种叫钢沉井的技 (CCTV super worksheet commentary abstracts) Now, the 163th bridge on the Yangtze River is underway - Yang Si harbor bridge. When completed, it will become the world’s largest double-decker suspension bridge. Building bridges on the third largest river in the world, the biggest difficulties now facing are the same as 60 years ago, “how to build bridge piers in the riverbed.” After thousands of years of scouring and sedimentation, the bottom of the Yangtze can scarcely find a solid bed foundation, so engineers use a technique called steel caisson