润扬大桥风化花岗岩工程特性与影响因素研究

由于风化会对岩石强度、刚度和耐久性产生重大影响，故在岩石工程勘察设计中需对其进行重点研究。风化是润扬大桥花岗岩类基岩岩体质量和桥基选址与设计的控制因素之一。系统的地质分析和多种测试结果表明，桥区风化壳厚度的变化很大，岩性以及地壳升降、断裂切割、卸荷作用、江水下切与入渗等地质作用是控制花岗岩风化作用及其风化岩分布的主要因素；桥区花岗岩易风化、卸荷敏感，处于化学风化的早期阶段：细密的蚀变裂隙对岩石强度起着控制作用。在此基础上讨论了风化带来的主要岩土工程问题以及桥型方案、基础选址与设计、地基参数取值以及风化因素控制等方面的工程对策。

ENGINEERING PROPERTIES AND AFFECTING FACTORS OF WEATHERED GRANITE IN FOUNDATIONS OF RUNYANG BRIDGE

Weathering,being a natural process that decreases rock strength,stiffness and durability,is specially concerned in investigation and design of rock engineering. Runyang Bridge is the longest suspension bridge in China and the third longest one in the world by now. Weathering strongly affects the quality of the bedrock of granite and therefore controls the siting and designing of the bridge foundations. Systematical geological analyses and a set of field and laboratory tests were carried out. It is found that the lithology and the geological agents,including vertical tectonic moving,fracturing,unloading,river eroding and infiltration,are the main factors affecting the granite weathering and the various distribution of weathered rockmass at the bridge site. The study indicates that the granite is susceptible to weathering and unloading,and in early chemical weathering stage. The main geotechnical issues due to weathering and correlated countermeasures about selection of bridge type,site and design of the tower foundations,determination of bedrock parameters and control of further weathering of bedrocks are further discussed.