# Seismic Responses of GRS Walls with Secondary Reinforcements Subjected to Earthquake Loading
## 1 Introduction  
Geosynthetic-reinforced soil (GRS) walls have been successfully used in many practical applications as alternatives to conventional retaining walls due to their good performance, lower cost, and economic efficiency. Several guidelines for the design of practical GRS walls are available from the American Association of State Highway and Transportation Officials (AASHTO) [1], the British Standards Institution (BSI; BS 8006-1:2010+A1:2016 (BSI)) [2], the United States Federal Highway Administration (FHWA) [3], and the United States National Concrete Masonry Association (NCMA) [4]. Applications using geosynthetic reinforcements are commonly designed with a vertical spacing (VS) of 0.6 m. This relatively large spacing may lead to a high reinforcement strength near the back of the wall facing, which may result in a connection failure [5, 6]. To alleviate the primary reinforcement load and increase internal stability, shorter reinforcements (referred to as secondary reinforcements) set between primary reinforcements have recently been utilized. Several researchers have evaluated the secondary reinforcement effect on GRS wall performance under working stress conditions using analytical methods [7,8], experimental studies [9, 10, 11], field tests [12, 13, 14], and numerical analyses [5, 6]. For example, the limit equilibrium method was used by [PERSON] and [PERSON] (2006) [7], and [PERSON] et al. (2014) [8], to investigate the effect of secondary reinforcements in GRS walls. Additionally, [PERSON] et al. [9, 10] utilized a geotechnical centrifuge to study the failure mechanisms of geosynthetic soil slopes with secondary reinforcements. Furthermore, [PERSON] et al. [12] and [PERSON] et al. [13, 14] constructed and monitored GRS walls with/without secondary reinforcement in the field to understand the performance of GRS walls with secondary reinforcement by comparing the wall facing deflection, the strains of primary and secondary reinforcements, etc., of the GRS walls. [PERSON] et al. [5, 6] employed finite difference analysis (FDA) to evaluate the secondary reinforcement effect on the performance of GRS walls. These results confirmed that installing a secondary reinforcement between primary reinforcements can reduce the lateral displacement of the wall facing, the bulge of the wall facing, the connection load, and the maximum reinforcement load in the primary reinforcement. Although a large amount of research has been conducted on the performance of GRS walls with secondary reinforcement under working stress conditions, concerns still remain regarding the response of secondary reinforcements to seismic motions and the benefits of secondary reinforcement under dynamic conditions. Extensive studies, experimentally and numerically, have been carried out to analyze the performance of GRS walls during seismic loading, including the relative lateral facing displacement, lateral earth pressure, crest settlement, acceleration amplification, and tensile reinforcement in reinforcement layers [15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26]. The results of these studies showed that critical factors including reinforcement length, wall height, soil stiffness, soil strength, earthquake motions, and reinforcement spacing played important roles in the performance of GRS walls during seismic loading. In this study, a series of dynamic finite element analyses were conducted to investigate GRS walls under seismic loading to explore the effect of secondary reinforcement on the seismic performance of the GRS walls. First, the finite element procedure was validated by simulating a field GRS wall with secondary reinforcement and modular-block geosynthetic-reinforced soil (MB-GRS) walls built by [PERSON] et al. [5, 13, 14] and [PERSON] et al. [27], respectively.