铜陵公铁两用长江大桥主桥施工关键技术

Key Techniques for Construction of Main Bridge of Tongling Changjiang River Rail-cum-Road Bridge

铜陵公铁两用长江大桥主桥为主跨630m的五跨连续钢桁梁斜拉桥,三主桁三索面结构型式,采用钢绞线斜拉索。3号主墩采用沉井基础,下部钢沉井采用整节段工厂制造、整节段船舶运输、整节段浮态接高新技术,并通过球阀控制连通管快速注水定位着床;采用贴面爆破法辅助沉井在卵石胶结地层中下沉。3片主桁均由全焊桁片拼装而成。桁片由工厂制造、在船舶上竖立存放运输。桁片在现场安装时,根据不同预拱度,采用"下弦杆结点→斜杆结点→上弦杆结点"和"上弦杆结点→下弦结点→斜杆结点"两种顺序对接,以方便接头折角调整。跨中采用桁片式钢梁整体合龙。斜拉索单根钢绞线索力的均匀性采用等值张拉法和智能控制张拉系统进行控制,并通过群锚千斤顶张拉进行整束索力调整。

The main bridge of Tongling Changjiang River Rail-cum-Road Bridge is a five-span continuous steel truss girder cable-stayed bridge with a main span of 630 m.The bridge has the structural type of three main trusses and three cable planes and the stay cables supporting the bridge are the steel wire strand cables.The foundation for the main pier No.3 is the caisson foundation,of which the lower part steel caisson was constructed,using the new techniques of fabricating the caisson in full lifts in the workshop,transporting in full lifts by ship and extending the height of the caisson in full lifts in the floating state.The steel caisson was landed onto the riverbed and positioned by fast filling water into the caisson through the connection pipes controlled by ball valves and in the pebble cementitious stratum,the caisson was sunk down with the aid of the surface blasting method.The three main trusses were all assembled from the all-welded truss units.The truss units were fabricated in the workshop,stored in vertical positions on board a ship and transported by the ship.When assembled in the field,the truss units were assembled according to the different cambering in the two sequences of the lower chord panel points→diagonal panel points→upper chord panel points and the upper chord panel points→lower chord panel points→ diagonal panel points to facilitate the adjusting of the kinking angles of connection.At midspans,the truss unit steel girders were closed integrally.The force uniformity of a single steel wire strand of the stay cables was controlled by the equivalence tensioning method and the intelligently controlled tensioning system and the force of a full stay cable was adjusted by the tensioning of the group anchor jacks.