# Analysis of Vertical Earth Pressure Acting on Box Culverts through Centrifuge Model Test
## 1 Introduction  
Infrastructure is a basic building block of social production or economic activity. It includes industrial infrastructure, such as dams, roads, ports, power plants, and telecommunication facilities, and social welfare and environmental infrastructure, such as schools, hospitals, and parks [1]. The global construction market in 2019 was estimated to be close to $500 billion, and the construction market is essentially a large-scale infrastructure market [2]. Owing to the demand for replacing old infrastructure and constructing transportation infrastructure, construction worth tens of billions of dollars is underway or planned in Asia (Indonesia, Laos, China, and Middle East countries), as well as Europe, Canada, and Africa [3]. Recently, the use of \"underground infrastructure\" in urban underground spaces is increasing owing to the lack of surface space and the need for a better environment [4]. Representative underground infrastructure can be categorized as follows: (1) buried utilities such as water, electricity, gas, and telecommunications; (2) foundations of buildings and bridges; and (3) underground structures, such as tunnels, subways, buildings, and mines. Among these, there is a strong demand for the construction of buried utilities to provide various services to residents; moreover, the surface infrastructure installed on the ground and the relationship between surface structures and underground structures are important [5, 6]. Therefore, to protect buried utilities from underground environments, such as groundwater and earth pressure, and surface loads, such as superstructure and traffic loads, box culverts are buried underground, and utilities are installed inside. Box culverts are mainly composed of materials of cast-in-place or precast reinforced concrete. The load applied to a box culvert is determined by the characteristics of the ground and the geometry and stiffness of the structure itself [7]. Currently, the vertical load acting on the upper section of a box culvert can be calculated theoretically as the sum of the ground surface load (superstructure or traffic load) and the earth pressure of the soil above the box culvert. However, the actual load may deviate from the theoretical value owing to the construction method involved (embankment or trench installation) and soil-box culvert interaction characteristics [8; 9; 10; 11; 12; 13]. In addition, even if the same vertical load acts on the upper section of the box culvert, the resulting stress may differ depending on the position of the upper section because the inside of the box culvert is an empty space [14]. This stress is the vertical earth pressure acting on the upper section of the box culvert. In this study, considering the increasing pace of urban underground space development, the vertical earth pressure acting on a box culvert used for electric power or gas transport is analyzed. The vertical earth pressure acting on box culverts has been investigated by various researchers with a focus on the characteristics of soil-structure interaction. Recently, scale model tests and numerical analysis were conducted according to the structural form (flat seam, round hinged, integral, and mortise) of the prefabricated reinforced concrete box culverts, stress-strain self-sensing precast-box culvert smart element design and experimental verification under loading conditions were analyzed [15; 16]. In addition, studies on the effect of load and the use of box culverts in tunnels or railway tracks are being actively conducted [17; 18; 19]. These studies have mainly considered the width and height of the box culvert and the height of the backfill soil in numerical analyses, centrifuge tests, and field tests [19; 20; 21; 22; 23; 24; 25; 26]. However, even the centrifuge model tests or field tests conducted in sophisticated and controlled environments are affected by the inherent uncertainty of soil and errors in the measurement process [27].