The structure of the cable-stayed bridge with super long span over 1 000 m is complex and the allowable construction tolerances thereof are small.The distances between the pylons of the bridge and the banks are far and the construction survey precision required for the pylons is high.To improve the construction survey precision,the Hutong Changjiang River Rail-cum-Road Bridge being built at present was cited as an example and the key techniques for layout of the primary horizontal construction control network,for control survey of the large open caissons and construction survey and deformation survey of the very high pylons of the bridge were researched.Based on the structural characteristics and the related environmental conditions of the bridges of the same kind,the construction control network was designed in order to accommodate the precision requirements of the successive construction.The co-axial target beacons were designed and the river-crossing trigonometric leveling steps were optimized to improve the trigonometric leveling precision.The verticality of the open caissons was surveyed,using the new type of the high precision vertical displacement measurement system and the posture of the caissons was measured and controlled intelligently.The datum transit projection method was proposed for control of the verticality of the pylon columns as well as for estimation of the survey precision in order to resolve the problem of the survey and control of the verticality of the high pylons.The rational method for observation of the deformation of the pylon columns was selected to accommodate the practical need of the construction.%千米超大跨径斜拉桥结构复杂且施工允许偏差小、塔柱离岸远但施工测量精度高,为提高其施工测量的精度,以在建的沪通公铁两用长江大桥为例,对其首级施工控制网布设、大型沉井控制测量、超高塔柱施工测量及变形测量等关键技术进行研究.根据该类结构的特点和环境条件进行首级平面施工控制网设计,以满足后续施工精度要求.设计同轴觇标灯优化跨河三角高程程序,以提高跨河三角高程的测量精度.采用新型高精度竖向位移测试系统测量沉井垂直度,智能化测控沉井姿态.提出采用基准投点法控制塔柱垂直度并估算测量精度,解决超高塔垂直度测控的难题.合理选择观测方法进行塔柱变形观测,以满足实际施工需要.
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