马鞍山公铁两用长江大桥Z3号墩承台施工关键技术  

Key Construction Techniques for Pile Cap of Pier Z3 of Maanshan Changjiang River Rail-cum-Road Bridge

作　　者：徐京海 潘博[2] XU Jing-hai;PAN Bo(China Railway Shanghai Group Co.,Ltd.,Shanghai 200071,China;China Railway Major Bridge Engineering Group Co.,Ltd.,Wuhan 430050,China)

机构地区：[1]中国铁路上海局集团有限公司建设部,上海200071 [2]中铁大桥局集团有限公司,湖北武汉430050

出　　处：《世界桥梁》2022年第3期39-44,共6页World Bridges

摘　　要：马鞍山公铁两用长江大桥主航道桥为(112+392+2×1120+392+112)m三塔钢桁梁斜拉桥,Z3号墩基础承台为哑铃形结构,顶、底面高程分别为+4.5 m、-5.0 m,平面尺寸为36.8 m×81.8 m。结合桥位处地质情况,承台采用PC工法组合桩围堰进行基础施工,围堰平面尺寸为87.6 m×42.2 m、高30 m,其侧板采用∅820 mm×14 mm锁口钢管桩+拉森Ⅵ型钢板桩交替布置的组合桩形式,围堰高度范围内设3层内支撑,经验算围堰结构满足规范要求。施工中,采用基准桩定位、分阶段消除累积误差以及精确调整合龙等技术保证围堰顺利合龙;通过深基坑井点降水开挖技术保证开挖面始终处于无水环境;通过动态监测技术对基坑支护结构受力及变形实施动态监测确保深基坑施工安全;采用优化原材料配合比及承台混凝土内分层布设循环冷却水管等措施有效减小混凝土水化热,保证承台混凝土施工质量。The main navigation channel bridge of Maanshan Changjiang River Rail-cum-Road Bridge is a steel truss girder cable-stayed bridge.The bridge has three pylons that creates two main spans of 1120 m,two side spans of 392 m and two back spans of 112 m.The pier Z3 is supported on a dumbbell-shaped foundation that measures 36.8 m by 81.8 m in plan,with top and bottom elevations of+4.5 m and-5.0 m,respectively.To accommodate the geological conditions at the bridge site,the pile cap was a prestressed concrete structure that was cast with the assistance of a composite cofferdam measuring 87.6 m by 42.2 m,30 m high.The cofferdam consisted of∅820 mm×14 mm interlocking steel pipe piles,the LarsenⅥsteel sheet piles,and three layers of inner bracings that were placed with specified vertical intervals along the cofferdam height.The cofferdam structure was confirmed meeting the code requirements.Benchmark piles were installed for cofferdam positioning,and the accumulated bias of the structure during construction was eliminated in stages and the geometry of the closure gap was accurately adjusted,aiming to ensure the smooth closure of the cofferdam.To assure that the foundation pit excavation was constantly carried out in dry environment,water inside the cofferdam was discharged via the dewatering wells.During the foundation pit excavation,the load bearing performance and deformation of the supporting structure of the foundation pit was under real-time monitoring to ensure the construction safety.To address the hydration heat of concrete,the mixing proportion of the raw materials were modified,layers of water cooling pipes were implemented,as a result,the casting quality of the pile cap concrete was under control.

关 键 词：斜拉桥 承台 PC工法组合桩围堰 深基坑井点降水开挖 施工监测 大体积混凝土 施工技术 

分 类 号：U448.27[建筑科学—桥梁与隧道工程] U445.556[交通运输工程—道路与铁道工程]