Due to the development of national industries and rapid economic growth, urban areas are becoming more sophisticated and overcrowded. In addition, in order to utilize underground space more efficiently rather than above ground, the size of underground structures is also increasing in depth and size. In order to relieve traffic problems in large cities and promote efficient development of the country, urban railways, tunnels, underpasses, and underground shopping malls are being built.

Underground structure construction methods are implemented by selecting the optimal construction method by comparing and reviewing various factors such as stability of ground conditions, relationship with existing structures, constructability, traffic volume, and economic feasibility, depending on the local conditions for construction.

The selection of an applied method to install an underground structure is based on a comprehensive review and analysis of the linear conditions, the current status around the route, the geological condition of the surrounding ground, and the topographic conditions of the groundwater level, so that it is suitable for the purpose and specifications of the target object, is easy to construct, and is economically optimal construction method must be selected.

One of the most commonly used construction methods is the cut-and-cover construction method. In order to secure the passage of vehicles and pedestrians and install underground structures, it is essential to install temporary structures to ensure constructability and safety for a long period of time. The intermediate pile, which is a support-type H-beam temporary structure installed to secure work space and support the upper load, is installed in the underground concrete structure, and the upper intermediate pile is removed after pouring the concrete for the bottom plate of the structure. The intermediate piles that remain after the underground structure is installed become integrated with the bottom slab concrete of the structure and affect the structure.

Intermediate piles, which are inevitably installed depending on site conditions and ground conditions, affect the bottom of the structure by adding to the ground reaction force applied to the entire bottom of the underground structure. However, only the design standards for openings are presented in the design standards for openings in the national construction standard slab system, and only the regulations for submitting detailed drawings are specified in the standard specifications, but design standards for buried parts are not provided.

Even if you look at the current OO urban railway construction site, there is no structural review and interpretation that may appear in the presence of H-shaped steel, which is an intermediate pile, and most sites are being constructed after waterproofing by applying the opening.

Accordingly, in this study, the impact of intermediate piles on the slab bottom plate was structurally examined, including the bearing capacity according to soil characteristics by the width of the bottom plate and the thickness of the slab, and the bending moment and shear force that the upper load exerts on the structure by case depending on the presence or absence of intermediate piles. Based on these results, reinforcement measures and design standards for buried parts were presented.