矮寨大桥基础岩体稳定问题研究

由于各构筑物及其与高陡边坡紧邻，准确把握构筑物围岩的稳定性及其相互影响，是设计方案能否成立的关键。总结分析矮寨大桥基岩稳定的4个方面的关键问题，并介绍大桥基础岩体勘察所采用的多种手段、主要的地质缺陷、基岩稳定分析结果及施工期监测结果。开挖揭露的地质条件、稳定分析及监测结果表明，多种技术方法是全面认识岩体工程地质条件的必要手段。矮寨大桥基岩的稳定问题集中在两岸高陡边坡上，设计荷载并未引起岩体产生明显变形，各构筑物之间相互影响不明显。只要通过适当的加固措施保证边坡岩体的稳定，桥基岩体稳定性就可以得到保证。设计采用的塔梁分离式悬索桥结构，以及各构筑物的布置是可行的，研究成果支撑了结构设计上的创新。隧道锚因围岩“夹持效应”而产生强大的抗拔能力。由于国内外大型悬索桥采用隧道式锚碇不多，对隧道锚碇围岩的岩石力学问题研究还不够深入，其承载能力可能被严重低估。

STUDY OF ROCK FOUNDATION STABILITY OF AIZHAI BRIDGE

Due to both the distance between constructions and the distance between construction and high-steep slope are quite small，grasping the stability of foundation rock and mutual effects between constructions accurately is crucial to the feasibility of design scheme. Four key problems concerning stability of foundation rock of Aizhai suspension bridge are summarized. Comprehensive approaches to investigate the bridge foundation rock masses are introduced，as well as main geological defects，the stability analysis and monitoring results of foundation rock masses during construction stage. The geological conditions exposed during excavation，stability analysis and monitoring results show that comprehensive survey approaches are indispensable to fully understand the geological conditions of rock masses. The stability problems of Aizhai suspension bridge focus on the high-steep slopes of two banks. Design load never causes significant deformations；and mutual effects between constructions are not obvious. The stability of rock foundations can be guaranteed if the high-steep slopes are reinforced appropriately. The tower-beam-separation design and the arrangement of constructions are feasible. The studies of foundation rock stability give support to the innovation in structural design. Tunnel-type anchorage can generate very huge pull-resistance capability caused by gripping effect from surrounding rock masses. Because the tunnel-type anchorages used in large suspension bridges at home and abroad are limited，and the researches on rock mechanics problems of surrounding rock masses of tunnel-type anchorage are not deep enough，the bearing capacity of tunnel-type anchorage may be seriously underestimated.