川藏铁路线V形深切河谷地形地震放大效应数值模拟

V形河谷场地能产生地震动放大效应,并加剧地震的破坏作用和灾害效应。基于高性能离散元软件MatDEM,对规则V形河谷以及真实河谷地形下的放大效应进行数值模拟研究。结果表明,对于规则V形河谷,在地震波水平入射的情况下,背波坡面产生明显的地震动加速度放大效应,并在临近谷底处最为强烈;随着河谷坡角的增大,放大效应增大。数值模拟结果和解析解具有一致的趋势和规律,并符合现场观测现象。将模型进一步应用于川藏铁路线日扎深切河谷的分析,发现地形微小的转折将会影响到波的传播,临近谷底处的加速度放大效应与规则地形较为一致。离散元法能有效地模拟河谷中地震波的传播、反射、散射等现象,可用于川藏铁路沿线复杂条件下的动力作用灾害效应分析。

Numerical Simulation Study on Seismic Magnification Effect of V-shaped Deep-cut Valley on Sichuan-Tibet Railway Line

V-shaped river valleys can produce ground motion amplification effects,and aggravate the destructive and disaster effects of earthquakes.Based on the high-performance discrete element software MatDEM,a numerical simulation study on the amplification effect of regular V-shaped valleys and real valley topography is carried out.The results show that for regular V-shaped valleys,when seismic waves are incident horizontally,the back-wave slope produces an obvious amplification effect of ground motion acceleration,and it is most intense near the valley bottom.The amplification effect increases as the valley slope angle increases.The numerical simulation results are consistent with analytical solutions in the trends and patterns,and agree with the field observation.The model is further applied in the analysis of the Rizha deep-cut valleys.It is found that small turning would affect wave propagation,and the acceleration amplification effect near the valley bottom is basically consistent with that of regular terrains.The discrete element method can effectively simulate the propagation,reflection,and scattering of seismic waves in river valleys.It can also be used for the analysis of dynamic and disaster effects under the complex conditions along the Sichuan-Tibet railway line.