Interaction of Underground Cavities with Stabilized Urban Excavation by Nailing and Anchorage

Abstract
One of the most important geotechnical issues is the stabilization and deep excavation of the city, which many research has been done about it., especially in recent decades. One thing that adds to the complexity and challenge of such projects is the existence of cavities and empty spaces in the vicinity of the excavation. Therefore, careful study and in-depth analysis play a crucial role in such projects. In this research, we try to examine this issue from different aspects and its practical result use in future projects. Due to the fact that the two methods of anchorage and nailing are the most widely used methods in strengthening and stabilizing the excavations, these two methods were selected also interaction of excavation-underground cavities were investigated. parameters such as the cavity depth, the distance of the cavity from the excavation, the diameter of the cavity, and the thickness of the cavity cover, have been investigated in this research. In this research, for analysis and modeling, PLAXIS 2D finite element software has been used with the assumption of plain strain and hardening soil model which is suitable for drilling. The results of the analysis showed that the horizontal displacement of the excavation increases due to the presence of cavities and the sensitivity of the cavities stabilized with the anchorage method is greater than the nailing method. The greatest effect of the cavity on the behavior of excavation, on the one hand, is special critical distances and depths. Studies have also shown that the field of soil deformation changes despite the cavity, but it will not have a significant effect on the forces created in consolidating elements. On the other hand, drilling operations near cavities can lead to changes in the internal stresses of the cavity covering elements that must be considered in the design.