黄土边坡暗穴对公路桥梁的致灾机理分析  

Analysis of disaster-causing mechanism of loess slope hidden cave on highway bridge

作　　者：黄强兵[1] 彭建兵[1] 

机构地区：[1]长安大学地质工程系国土资源部岩土工程开放研究实验室,西安710054

出　　处：《水文地质工程地质》2007年第4期1-5,共5页Hydrogeology & Engineering Geology

基　　金：交通部西部重点交通建设科技攻关项目(2001318-81213)

摘　　要：根据黄土暗穴空间走向的不同,将黄土边坡桥基下伏暗穴对桥梁的危害归纳为倾倒破坏模式和滑塌破坏模式。采用二维有限元方法,对黄土边坡顺沟向桥基下伏暗穴对桥梁的致灾机理进行了数值模拟分析后得出:黄土暗穴引起的桥梁变形以垂直下沉变形为主,水平方向的变形不明显;随着黄土暗穴的发展,其半径由0.2m逐步增大至0.5m、1.0m时,桥梁失稳主要表现为桥基下伏黄土暗穴周围的舌状塑性区沿45°方向放射性扩展,与桥基附近土体塑性破坏区相贯通导致桥梁不均匀沉降并向沟外侧倾倒破坏。同时,通过有限元法进行模拟计算,得出了桥梁安全时顺沟向桥基下伏黄土暗穴的临界埋深与其半径之间关系可用对数函数关系式表示,其相关系数反映拟合关系具有很高的精度。According to different spatial strikes of loess hidden cave, the disaster-causing effect of loess hidden cave on highway bridge is divided into two modes： toppling-failure mode and sliding-failure mode. The disaster-causing mechanism of loess hidden cave locating under highway bridge foundation along gully is simulated by two-dimension finite element method. It is pointed that the vertical deformation of bridge foundation is main and the horizontal displacement can be omitted. Moreover, when the highway bridge foundation settlement increases with the radius of loess hidden cave changing from 0.2m to 1.0m, the surrounding ligulate plastic zone of loess hidden cave extends along the angle of 45^o and then interpenetrates with plastic zone of bridge foundation surrounding soil mass. When the radius of loess hidden cave increases to 0 .5m, the vertical settlement of highway bridge foundation is up to 9cm which exceeds the allowable value 5cm and the bridge begins to collapse inclined to the valley. Meanwhile, the simulation was conducted repeatedly, the results show that the relationship between critical buried-depth of loess hidden cave under bridge foundation along gully and its radius can be expressed with logarithmic function when the bridge is safe, and its correlation coefficient reflects that the fitting relationship has a higher accuracy.

关 键 词：桥梁工程 黄土暗穴 危害模式 数值模拟 致灾机理 临界埋深 

分 类 号：U445.7[建筑科学—桥梁与隧道工程]