# Analysis of the Dynamic Behavior of Multi-Layered Soil Grounds
## 1 Introduction  
Earthquakes are one of the most common natural disasters on Earth and are extremely destructive. Earthququakes cause seismic waves to propagate through the Earth's crust, with numerous effects on its soil and foundations, such as seismic wave amplification, earthquake-induced liquefaction, and effects on infrastructure, which have been modeled in various studies [1]. Earthquakes propagate seismic waves in soil, and different types and layers of soil have different effects on the propagation and response of seismic waves. Therefore, to assess the stability and safety of the ground during earthquakes, an in-depth understanding of the response behavior of multi-layered soils is required. A lot of studies have been conducted using 1 g shaking-table test and numerical analysis methods for single-layer soil [2, 3, 4, 5, 6, 7, 8, 9]. For multi-layered soil grounds, 1 g shaking-table tests are designed to simulate the interactions between different soil layers under seismic conditions and the effects of earthquakes on buildings and infrastructure. The following are some studies related to multi-layered soil. [PERSON] et al. (2016) demonstrated the amplification effect that occurs in multiple soil layers by performing centrifuge tests on three soil layers. The results they obtained comprised only experimental data, and because the field size was too small, it could not reflect the amplification effect well [10]. [PERSON] and [PERSON] (2019) combined 1 g shaking-table tests and the numerical analysis program OpenSees to evaluate the seismic behavior of the liquefiable sub-layer and its impact on the seismic ground response [11]. [PERSON] et al. (2022) conducted 1 g shaking-tabletests to study the dynamic behaviors of multi-layered soil, but the established soil layer only had two layers and they used soil layers of the same material, which cannot represent multi-layered soil well [12]. [PERSON] et al. (2021) used ABAQUS to conduct a modeling analysis on single-layer soil and three-layer soil to verify the interactions between multiple layers, but their findings were not supported by experimental data [13]. [PERSON] et al. (2012) investigated the liquefaction mechanism of layered sand through shaking-table tests and numerical analysis [14]. [PERSON] et al. (2020) used the finite-element software CyclicTP to analyze the dynamic response of the foundation of a layered homogeneous soil system [15]. [PERSON] et al. (2023) used a 1 g shaking table to study the improvement and liquefaction of drainage piles in a layered soil model [16]. [PERSON] et al. (2022) studied the seismic responses of abutment models under different soil types through large-scale shaking-table tests and numerical simulations, analyzing the dynamic response under three soil types (silty clay, clay-gravel layer, pure gravel soil) [17]. [PERSON] et al. (2018) investigated how compaction affects the behavior of gravel embankments under seismic conditions [18]. [PERSON] et al. (2023) measured the performance parameters of permeable concrete by changing the mixture ratio of eleven types of concrete, controlling the size of the aggregate and four degrees of compaction [19]. [PERSON] et al. (2024) compared the effects of tier offset, soil density, and reinforcement layout on the seismic response of tiered reinforced soil retaining walls (TRS-RWs) through numerical analysis [20]. Conducting a 1 g shaking-table test combined with numerical analysis enables the examination of how seismic waves travel through various soil layers. This approach helps in understanding the intricate patterns and characteristics of seismic wave propagation within multi-layered soil systems. Seismic waves may be amplified or attenuated in multiple layers of soil, depending on the nature and structure of the soil layers. Through dynamic analysis, the amplification effect or energy loss of different soil layers on seismic waves can be quantified, and the response of multi-layered soil grounds to seismic waves can be evaluated.