# Dynamic Characteristics of Post-Cyclic Saturated Loess
## 4 Discussion
As seen in Figure 15a, before pre-seismic, the boundaries of particles are clear and the particles are arranged in a mosaic, whereas the contact among grains is surface contact. There are many more trellis pores, a relatively uniform distribution, and an obvious overhead pore structure. However, the structure of the soil changed significantly after pre-seismic and over-consolidation. According to Figure 15b, when the soil is normally consolidated after the pre-seismic, the particle boundary is still obvious; however, the contact among grains occurs more as point contact and boundary contact. The connection between the particles is not as tight as before. There are still plenty of pores; however, the trellis pore is no longer obvious due to the deformation of pre-shock. Furthermore, the uniformity of the pore distribution becomes better. Note that the most conspicuous change between Figure 15a,b is a large number of pores connected in tiny cracks in Figure 15b, resulting from the loosening and rearrangement of the gains during vibration. According to Figure 15c,d, after OCR reached two, the particle boundary became blurred, resulting in the consolidation and compaction of soil, and the number of medium and large pores reduced significantly. Moreover, the small gaps formed by pore connection after the cyclic shear were also healed locally under the action of over-consolidated pressure. After the OCR reaches three, only a small number of medium and large pores is distributed in the loess. The compaction effect of soil particles is more obvious. According to Figure 15e, when the OCR reaches four, the boundary of soil particles is blurred and the particles of different sizes are gathered together. The particles are not easy to distinguish and the porosity content is significantly reduced. Based on the analysis and discussion shown above, combined with the results shown in Figures 8, 9 and 11-14, it is illustrated that the stiffness of the loess has an obvious loss, resulting in the changes of particle arrangement and the loosening of connection among particles after pre-seismic load. Meanwhile, the penetration of medium and large pores caused by cyclic load makes the accumulation and transmission of pore water pressure much easier, which can lead to an obvious reduction in the effective stress as well as a significant enhancement of the viscosity of the soil. The reconsolidation effect on the soil after pre-seismic makes the loose soil gradually compact. With an increase in the OCR, the consolidation pressure continues to increase, and the compaction effect on the loess is gradually increased. Since the pores of the soil are obviously reduced and the connected pores result in pre-shock being gradually blocked under the compaction effect, the factual contacting area between the particles increases and the connection becomes much closer. Thus, the stiffness of the loess is significantly increased, the viscosity tends to decrease, and the deformation potential of the loess gradually tends to decrease [54]. This study investigates the characteristics of nonlinear dynamic properties of the post-cyclic saturated loess and analyzes the influence of pre-shock and reconsolidation on the dynamic properties of the saturated loess. Based on the test results and analysis, suggestions to aid subsequent research are as follows: (1) Seismic liquefaction is not only a kind of seismic geological hazard in the loess region but also a significant trigger. For loess landslide and mudflow. Thus, studies on liquefaction behaviors of the post-cyclic saturated loess will be helpful in understanding post-earthquake landslides.