既有线间小截面桥墩施工及加固技术

Construction and Reinforcement Technology of Small Cross-Section Pier Between Existing Lines

为解决既有线间小截面桥墩施工困难和拖拉施工中水平力过大、抗推刚度小、材料运输困难和加固场地有限等难题,结合北京黄村站人行跨线通廊拖拉法施工项目中LD墩所采取的施工方法和利用格构柱加固的方式展开研究。阐述了桥墩和格构柱的施工技术,并通过对比原桥墩、假设桥墩与上部结构摩擦系数为0.1、0.15和0.2的加固后桥墩和格构柱的应力和墩顶水平位移来反映加固措施的有效性。实践和分析结果表明:采用过轨泵送混凝土的施工方法大幅缩短了工期,保证了桥墩质量;利用格构柱加固后,小截面桥墩在施工过程中全截面受压,保证了结构安全;且加固后桥墩在摩擦系数不断增大的情况下桥墩应力基本保存不变,增大的水平力主要由加固支架来承担。最后针对顶推法施工中桥墩的设计提出一些思考,可在后续施工中提高经济效益和缩短工期等。

In order to solve the difficulties in the construction of small-section piers between existing lines,such as excessive horizontal force,low pushing stiffness,difficult material transportation and limited reinforcement site,a study was carried out based on the construction method adopted for LD piers in the construction project of the pedestrian crossing corridor at Huangcun Station in Beijing and the use of lattice columns for reinforcement.This paper expounded the construction technology of pier and lattice column,and reflected the effectiveness of the reinforcement measures by comparing the stress and horizontal displacement of pier top of the original pier and the reinforced pier and lattice column assuming that the friction coefficient between pier and superstructure is 0.1,0.15 and 0.2.The results of practice and analysis show that the construction method of pumping concrete through the rail greatly shortens the construction period and ensures the quality of the pier.After being strengthened by lattice columns,the pier with small cross-section is compressed in the whole section during the construction process,which ensures the structural safety.Moreover,when the friction coefficient of the reinforced pier is increasing,the stress of the pier is basically kept unchanged,and the increased horizontal force is mainly borne by the reinforcement bracket.Finally,some thoughts on the design of pier in incremental launching method construction are put forward,which can improve the economic benefit and shorten the construction period in the follow-up construction.