武汉杨泗港长江大桥锚碇型钢锚固系统施工关键技术

Key Construction Techniques for Section Steel Anchor System of Yangsigang Changjiang River Bridge in Wuhan

武汉杨泗港长江大桥主桥为主跨1700 m的双层公路钢桁梁悬索桥,该桥重力式锚碇由地下连续墙、帽梁、内衬、锚碇混凝土组成,采用型钢锚固系统(由后锚梁和锚杆组成)。锚碇基坑开挖后进行锚碇混凝土及型钢锚固系统施工,锚碇混凝土竖向分14层(每层分3块)浇筑,后锚梁和锚杆在工厂内加工制造,分批次随锚碇混凝土分层安装,通过定位支架(由后端支架、中间支架、前端支架、连接杆组成)进行空间位置调整。在该桥型钢锚固系统施工中,通过设置具有足够强度、刚度及稳定性的宽翼缘型钢定位支架,减小了分层混凝土浇筑对已定位后锚梁及锚杆精度的影响;通过无棱镜空间定位法控制锚杆前端中心位置,确保了锚杆安装精度,提高了锚杆测量速度、效率及安全性;通过对构件进行及时限位,避免了施工振动造成的构件位置偏移,有效减少了重复调整次数;通过两次钻孔成孔工艺确保了精制螺栓成孔精度。该桥型钢锚固系统安装用时120 d,其锚杆纵向偏位在10 mm内、横向偏差在5 mm内、锚固点高程偏差在5 mm内,均满足设计要求。

The main bridge of Yangsigang Changjiang River Bridge in Wuhan is a steel truss girder suspension bridge that accommodates two levels of roadway decks.The bridge has a main span of 1700 m.The gravity anchorages of the main cables consist of diaphragm walls,cap beams,inner linings,in-fill concrete as well as the section steel anchor system that incorporates rear anchor beams and anchor rods).After foundation pit excavation,the in-fill concrete was poured and the section steel anchor system was installed.The concrete was poured in fourteen layers(each layer was divided into three zones).Rear anchor beams and anchor rods were fabricated in the factory,installed along with the poured concrete in layers at the bridge site,and subsequently adjusted to the required attitudes via positioning frames that are formed of the back frame,central frame,front frame and connecting struts).During the construction of section steel anchor system,the wide-flange section steel positioning frame with sufficient strength,rigidity and stability was utilized to relieve the influence of layered concrete casting on the already-positioned rear anchor beams and anchor rods.The prism-free spatial positioning method was adopted to control the location of the front center of the anchor rods,to ensure the installation accuracy of anchor rods and improve the measurement speed,efficiency and safety of anchor rods.Timely restriction was applied to components to prevent vibration-induced displacement of components during construction,as a result,the repeated adjustments were also effectively cut down.A two-phase perforation was performed to ensure the bolt hole forming accuracy.The installation of the section steel anchor system lasted 120 d,the longitudinal and transverse displacements of the anchor rods were controlled less than 10 mm and 5 mm,respectively,and the elevation deviations of the anchor points were less than 5 mm,all meeting the design requirements.