汉宜铁路蔡家湾汉江特大桥施工技术

Construction Techniques for Caijiawan Hanjiang River Bridge on Wuhan-Yichang Railway

蔡家湾汉江特大桥主跨采用(64+120+168+120+56)m刚构连续梁。主墩167号、168号属深水基础,基础采用"先平台后围堰"的施工方案,梁部采用挂篮悬浇施工方案。根据不同的地质情况,桩基施工过程中选择4种不同类型的钻机,对出现岩溶的桩基,采取回填"片石+粘土"的处理方案;承台采取双壁钢套箱围堰法施工,并采用千斤顶整体下放围堰;承台大体积混凝土施工采取埋设冷却水管、延长混凝土初凝时间、蓄水养护等温控措施,有效防止了温度裂纹的产生;梁部0号块采用支架法施工,其他节段采用挂篮对称悬浇施工,并在刚构跨中合龙口设置了4 000 kN的顶推力。

The main spans of Caijiawan Hanjiang River Bridge were designed as a rigid-frame continuous girder with span arrangement（64＋120＋168＋120＋56） m.The foundations for the main piers No.167 and No.168 of the Bridge were of the deepwater foundations that were constructed by the method of setting up platforms first and installing cofferdams late and the girder atop the foundations was cantileveredly cast by form travelers.4 types of boring machines were selected for use in the construction of the pile foundations in accordance with the different geologic conditions.For the pile foundations where the karst cavity presented,the ground there was handled by backfill of pebbles and clay.The pile caps were constructed by the double-wall steel boxed cofferdams that were lowered down in integrity by jacks.In the construction of the massive concrete for the pile caps,a series of temperature control measures like the layout of water-cooling pipes,prolonging of initial setting time of concrete and storage of water for curing were taken and the thermal cracking was therefore effectively prevented.The segment No.0 of the girder was constructed on scaffolding while the rest of the segments were cantileveredly and symmetrically cast by form travelers.At the closure gaps of the midspan of the rigid frame,the 4 000 kN jacking force was applied.