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

doi:10.19657/j.geoscience.1000-8527.2021.020

Abstract

Abstract:

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.

Key words: discrete element, seismic wave, valley amplification effect, numerical simulation, MatDEM, deep-cut valley, Sichuan-Tibet railway

CLC Number:

P642

QUAN Xuerui, HUANG Yehuan, LIU Chun, GUO Changbao. Numerical Simulation Study on Seismic Magnification Effect of V-shaped Deep-cut Valley on Sichuan-Tibet Railway Line[J]. Geoscience, 2021, 35(01): 38-46.

Figures/Tables 13

Fig.1 Stacked particle discrete element models

Table 1 Macroscopic physical and mechanical properties of natural core

材料类型	纵波波速V_p/ (km/s)	横波波速V_s/ (km/s)	杨氏模量 E/GPa	泊松比λ	剪切模量 G/GPa	体积模量 K/GPa	密度 $ρ$ / (kg/m³)
岩石	5.234 5	3.364 8	61.635 7	0.147 9	26.846 9	29.178 2	2 371

Table 1 Macroscopic physical and mechanical properties of natural core

材料类型	纵波波速V_p/ (km/s)	横波波速V_s/ (km/s)	杨氏模量 E/GPa	泊松比λ	剪切模量 G/GPa	体积模量 K/GPa	密度 $ρ$ / (kg/m³)
岩石	5.234 5	3.364 8	61.635 7	0.147 9	26.846 9	29.178 2	2 371

Table 2 Average element mechanical parameters of the discrete element model

材料类型	切向刚度K_s/(kN/m)	法向刚度K_n/(kN/m)	断裂位移X_b/m	抗剪力F_s0 /GN	摩擦系数μ_p	单元半径/m	总单元数
岩石	22.5×10⁶	61.7×10⁶	7.82×10^-8	5.04	0.12	5	107 186

Fig.2 V-shaped valley model(a) and location of the monitoring point in the valley(b)

Fig.3 X-axis velocity field of a laterally incident sine wave in the river valley

Fig.4 Magnification factor of different positions in the river valley with different slope angles under horizontally incident wave

Fig.5 Absolute value of maximum acceleration at different positions of the river valley under horizontal incidence of different frequencies

Fig.6 Geological and structural profile of the Rizha river valley[26]

Fig.7 Slope model

Fig.8 Standard response spectrum

Fig.9 Artificial synthetic seismic wave

Fig.10 X-direction velocity field in the river valley at different time

Fig.11 X-direction acceleration magnification factor of the river valley when the earthquake loaded to 2.88 s

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