大型钢吊箱拉靠墩系统精确定位施工技术

Construction Technique for Accurate Positioning of Large Steel Boxed Cofferdam Using Pulling and Berthing Pier System

武汉二七长江大桥主桥为三塔结合梁斜拉桥,其3号墩位于深水中,采用钢吊箱实现承台干施工。为解决大型钢吊箱精确定位难题,经过方案比选,采用拉靠墩系统定位方案,该系统由上游拉墩和下游靠墩组成,拉墩设主拉缆和下拉缆,靠墩设交叉拉缆,顺桥向抛锚,设置边锚缆。施工准备后,利用拉靠墩系统进行钢吊箱初定位,使其平面位置基本就位;通过边锚缆系统、拉缆系统及夹壁舱不均衡灌水调整钢吊箱的平面位置、平面扭转及摆动、垂直度,使其平面偏位在±12mm内、扭角为58″、倾斜度为1/3 000,满足规范要求,实现了钢吊箱精确定位。

The main bridge of Wuhan Erqi Changjiang River Bridge is a three-pylon composite girder cable-stayed bridge. The pile cap of pylon pier No. 3 of the bridge is located in deepwater and was constructed in dry environment in large steel boxed cofferdam. To resolve the problem of accurate positioning of the large cofferdam the pulling and berthing pier system was used after comparison of the different positioning schemes. The pier system is composed of a pulling pier at the upstream side and a berthing pier at the downstream side, on the pulling pier, the main pulling cables and tie-down cables were set while on thg berthing pier, the crisscross pulling cables were set. The positioning anchors were cast into the river longitudinally along the bridge and the side anchoring cables were set. After construction preparation, the cofferdam was initially positioned by the pulling and berthing pier system to make the cofferdam basically set in place in plan position. By using the side anchoring cables, pulling cables and by means of non-uniform pumping of water into the bulks of the cofferdam, the plan position, plan torsion, oscillation and perpendicularity of the cofferdam were adjusted and the plan offsetting of the cofferdam was brought to be within ±12 mm, the torsional angle to be 58＂ and the inclination to be 1/3 000 so as to make the construction of the cofferdam meet the relevant requirements in the codes and eventually realize the accurate positioning of the cofferdam.