## 3 Characterization of Anchor Cable in FDEM
### Results  
#### 4.2.1 Dynamic Response Analysis of the Landslide-Anchorage Structure System  
Taking the landslide-anchorage structural system as a whole, the dynamic response characterization can reveal its failure process and mechanism, and ultimately provide theoretical basis and data support for the analysis of the entire dynamic evolution process. The PGA amplification factor is the ratio of the maximum acceleration at any point on the slope to the maximum acceleration at P0. Acceleration response analysis is mainly used in the finite element method [20] and in the discrete cell method, especially when applied in the FDEM, which can simulate the entire dynamic evolution process of the landslide. It is first necessary to determine the time point when an obvious collision between the blocks occurs during the sliding process, because when the sliding body undergoes an overall failure, the gravitational acceleration and the contact force caused by collision will affect the acceleration value at the monitoring point. Moreover, the conversion of static-dynamic boundary conditions is involved in the present paper, and it can lead to small fluctuations in acceleration during this process [23]. Therefore, the time history of acceleration at monitoring points in this section ranges from 0.1 s after the static-dynamic transition to the collision of sliding blocks. The variation of PGA amplification factor along different measurement lines (P0-P9 along the slope surface, P0-P14, P19-P4, P24-  
Figure 8: Comparison of variations in the PGA amplification factors for the unreinforced and cable-reinforced slopes. **(a)** Seismic intensity VII (1.1 s–11 s). **(b)** Seismic intensity VIII (1.1 s–9.66 s). **(c)** Seismic intensity IX (1.1 s–7.2 s). **(d)** Seismic intensity X (1.1 s–6.2 s). The dynamic response of the unreinforced slope and the cable-reinforced slope is inconsistent under dynamic load. Still, on the whole, the dynamic response of the cable-reinforced slope is weaker than that of the unreinforced slope. Taking seismic intensity VIII as an example, the PGA amplification factor at the slope surface can be lower by 4% on average, about 1.4% at P14-P0 in the horizontal direction, 3% at P19-P4, and 3.8% at P24-P7. This is attributed to the ability of prestressed anchor cables to strengthen the slope and form a more rigid whole with it, which can significantly reduce the PGA of the slope under dynamic load. As shown in Figure 9, the acceleration time history at P9 at the top of the slope also confirms this because the existence of a prestressed anchor cable, on one hand, improves the integrity and joint strength of the slope, and on the other hand, reduces the vibration acceleration of the slope. Moreover, it is also found that the PGA amplification factors of the unreinforced and cable-reinforced slopes at the slope surface are significantly larger than those inside the slope, which is due to the wave superposition effect that occurs as a result of the stress wave transfer to the free face. For both unreinforced and cable-reinforced slopes, there is a significant elevation amplification effect from the slope toe to 0.5 times the slope height, with the PGA amplification factor increases along the slope surface with the rise in elevation. However, from 0.5 times the slope height to the top of the slope, the PGA amplification factor decreases. The reasons for the above are multifaceted and complex: the structural plane and the newly generated fracture surface have the effect of attenuating the stress wave, but the free face formed by them will have the effect of amplifying the stress wave. These two effects of attenuation and enhancement compete with each other within the slope, and this is the cause for the decrease in the PGA amplification factor with the elevation at the macro level. In Figure 8, the variation of the PGA amplification factor with \(x\) coordinate at different elevations can be observed.