湖北巴东长江公路大桥斜坡稳定性研究

Study on stability of slope at Badong Yangtse Highway Bridge site

巴东长江大桥是连接209国道和巴东县长江两岸新城区的特大型公路大桥,为一简支梁斜拉桥,长900.5 m,主桥跨度388 m,桥塔高218 m,桥荷重大,安全等级高。桥位区地处长江三峡地质条件最复杂的地区,地形陡峻,河谷切割强烈,褶皱断裂密集,岩体破碎、力学性质差,滑坡、泥石流极为发育,其斜坡稳定性直接关系到大桥的安全。在分析论述桥位区斜坡工程地质条件的基础上,采用非线性弹塑性有限元及块体极限平衡理论模拟了斜坡稳定性,预测了三峡水库蓄水及大桥建成后斜坡稳定性的发展趋势。研究表明:桥荷载、库水位波动和地震是影响斜坡稳定性的诱发因素。水库蓄水及大桥建成后桥位区两岸斜坡稳定性明显变差,有沿T2b3/T2b2岩层交界面失稳的可能,必须加以处理。在分析了斜坡变形破坏对大桥的影响后,提出了处理措施的建议。

The Badong Yangtse Bridge is a large highway bridge across the Yangtse River, connecting the No.209 national highway to the new town of Badong County. The bridge is a kind of simply supported cable stayed bridge of 900.5 m length, of which the 388 m main span has two towers of 218 m high. The bridge's weight is huge and the safety requirement is high, The bridge lies in the middle part of the Three Gorges where the geological condition is the most complex area. There are cliffy landform, sharply incised valley, complicated geo-structure, heavily cracked rock mass, frequent landslide and common debris flows. The slope stability has directly effect on the safety of bridge. On the basis of investigating the bridge site's geotechnical condition, the stability of slope was simulated by nonlinear elastoplastic finite element method and block limit equilibrium principle. At the same time, the developing trend of the slope's stability was predicted while the reservoir storing and the bridge building up. The researches show that the bridge's weight, fluctuating water lever and earthquake are induced factors of slope's failure. The stability of the slope is sharply decreased after the reservoir storing and the bridge building up. The slope may slide along the interface between T2bJ and T2b2. Some control measures must be taken. In this paper the effect of slope failure on the bridge was analyzed. Finally, some suggestions about existed problems are proposed.