Investigation on performance of steel strut servo system braced deep excavation adjacent to existing buildings: a case study

In response to increasingly stringent safety and construction environmental impact requirements for urban underground engineering, this study investigates the performance of a steel strut servo system braced deep excavation adjacent to existing buildings, using a subway station project as a case study. A three-dimensional finite element model is established to analyze the behavior of the steel strut servo system during deep excavation, focusing on the deformation characteristics of soil and structural members, as well as the factors influencing the system's performance. The findings indicate a strong correlation between the deformation of soil and structural members and the excavation depth, with greater deformation observed at deeper depths. When excavation is completed, the maximum and minimum vertical displacement of soil mass are 24.3 and - 5.8 mm, respectively. The maximum total displacement of buildings A and B is 3.86 and 3.82 mm, respectively. The servo system can inhibit the displacement of diaphragm wall to some extent. The maximum values of the servo area and other areas are 25.21 and 40.4 mm, respectively. The axial force of the strut is mainly pressure, with a maximum value of - 2,883.4 kN. The horizontal displacement of diaphragm wall is sensitive to the change of servo system position and servo axial force value. The deformation control effect is best when all steel struts are controlled by servo system. When the servo system is set with 2 struts, the maximum value decreases as the position of the servo system moves down. In addition, the maximum displacement decreases with the increase of the servo axis force value. This research provides valuable insights for the design optimization and construction control of similar projects.