碎屑流是我国山区最危险的地质灾害之一,山区桥墩常受到碎屑流冲击而开裂、倾斜甚至倒塌,给山区桥梁建设、运营带来严重的安全隐患.采用离散元方法(discrete element method,DEM)和有限元方法(finite element method,FEM)耦合的三维数值模拟方法模拟了碎屑流对双柱式桥墩的冲击效应,并结合斜槽试验,验证了耦合方法的准确性,进一步分析了碎屑流冲击坡度、距离和体积密度对桥墩冲击力的影响规律.结果表明,最大冲击力与碎屑流冲击坡度、距离和体积密度分别呈幂函数(指数大于1)、幂函数(指数小于1)和线性正相关.冲击坡度、距离和体积密度对最大冲击力的敏感度值分别为 3.012、0.202、0.804,在桥梁碎屑流灾害防治时需重视冲击坡度和体积密度的影响.将冲击力的数值模拟值与流体动力学模型预测值对比分析表明,流体动力学模型理论公式能较好地预测桥墩所受的最大冲击力,最大预测误差低于 23.6%.相关研究结果可为山区桥梁碎屑流灾害防治与设计提供一定的参考依据.
Influential factors of the maximum impact force of rock avalanche flow on bridge piers using DEM-FEM coupled method
Rock avalanche flow is one of the most dangerous geological disasters in mountainous areas of China.Piers in mountainous areas are often cracked,inclined,or even collapsed by the impact of rock avalanche flow,which brings serious safety hazards to the construction and operation of bridges in mountainous areas.The impact of rock avalanche flow on double-column piers is simulated using a three-dimensional numerical simulation method linked with discrete element method(DEM)and finite element method(FEM).The chute test validates the accuracy of coupling method,and further analysis is done to determine how the impact slope,distance,and volume density of the rock avalanche flow affect the impact force of piers.The results show that the maximum impact force increases in the form of a power function with a power index great than 1 as the impact slope increases,and increases in the form of a power function with a power index less than 1 as the distance increases.The bulk density grows linearly with the greatest impact force.The sensitivity values of the impact slope,distance,and volume density of the rock avalanche flow to the maximum impact force are 3.012,0.202 and 0.804,respectively.The impact slope and volume density should be taken into consideration while preventing and managing bridge rock avalanche flow disasters.A comparison between the numerical simulation value of the impact force and the anticipated value of the hydrodynamic model shows that the theoretical formula of the hydrodynamic model can accurately predict the maximum impact force on the pier,and the maximum prediction error is less than 23.6%.The relevant research results can provide some references for the prevention and design of rock avalanche flow disasters in mountain bridges.