云桂高速铁路南盘江特大桥5号拱座边坡岩体卸荷带特征分析

云桂高速铁路南盘江特大桥为主跨416 m的上承式钢管混凝土拱桥,为云桂高速铁路的控制性工程之一。通过工程地质测绘、钻探及平硐勘探等方法和手段,查明特大桥5号拱座边坡岩体的卸荷性状,并在现场平板静力载荷试验的基础上,确定5号拱座基础的承载力,为特大桥的设计和施工提供可靠的地质参数。分析表明:南盘江特大桥5号拱座边坡岩体强卸荷带水平发育深度18~25 m,弱卸荷带水平发育深度26~43 m。边坡岩体具有卸荷带与风化带同时共存的双层地质结构特征。边坡岩体卸荷带发育的深度与边坡形态相关,且受地层岩性和地质构造影响严重。根据现场平板静力载荷试验及相关规范,确定5号拱座基础其基本承载力σ0处于742~867 k Pa。

The Characteristics of Rock Slope Unloading Fracture Zone of No.5 Abutment of the Super Long Nanpan River Bridge on Kunming-Nanning High-Speed Railway

The super long Nanpan river bridge with 416 m main span is a deck steel-pipe concrete arch bridge and one of the dominant key projects of Kunming-Nanning High-speed Railway. Based on engineering geological survey,drilling and footrill exploration,the characteristics of the rock slope unloading fracture zone are identified,and the bearing capacity of f No. 5 abutment foundation is determined via static plate-loading test in situ,and the geological data for the design and construction are provided. The results indicate that the horizontal depth of the strong unloading fracture zone is 18 ~ 25 m,and that of the weak unloading fracture zone is 26 ~ 43 m; the rock slope is characteristic of coexistent double geological structures of both unloading fracture zone and weathering zone; the development depth of unloading fracture zone is not only related to the shape of slope,but also to the formation lithology and tectonics; and the basic bearing capacity of the No. 5 abutment foundation falls within 742 ~ 867 k Pa according to the results of static plate-loading test and related specifications.