强涌潮水域埋置式承台双壁钢围堰的下放精度控制

嘉绍跨江大桥主桥埋置式承台采用无底双壁钢围堰施工,施工中主要采取定位导向系统、吊点荷载控制、测量监控等方法控制围堰下放精度。下放过程中,采用固定在群桩护筒和钢围堰上的特制定位导向系统控制围堰平面偏位和垂直度;采用计算机控制系统监控吊点荷载,指导围堰舱壁内的加、卸载以及围堰内、外的吸泥;采用测量监控系统分析、计算围堰姿态,指导围堰的下放及纠偏施工。通过对围堰下放精度的控制,围堰下放平面偏位保持在5～8cm,垂直度达到1/400以上,均满足规范要求。

Accuracy Control of Lowering of Double-Wall Steel Cofferdams for Embedded Pile Caps in Strong Tidal Bore Water Area

The embedded pile caps of pier foundations of the main bridge of the Jiashao River-Crossing Bridge were constructed by the double-wall steel cofferdams without bottom.In the construction,the accuracy of lowering of a cofferdam was controlled mainly by the method of the positioning and guiding systems,the lifting point load management,survey and monitoring.As the cofferdam was lowered down,the special positioning and guiding systems fixed on the group pile steel casings and cofferdam were used to control the planar offsetting and perpendicularity of the cofferdam.The computer system was used to monitor and control the lifting point loads and to guide the loading and unloading inside the walls,the dredging inside and outside of the cofferdam and the survey and monitoring systems were used as well to analyze and calculate the status of the cofferdam and to guide the lowering and offsetting rectifying.By means of the accuracy control of the lowering,the planar offsetting of all cofferdam was kept within 5～8 cm and the perpendicularity greater than 1/400,which all satisfactorily met the relevant requirements in the codes.