# Improved Subsidence Assessment for More Reliable Excavation Activity in Tehran
## 1 Introduction
The NATM is used extensively in several nations to build tunnels through rocks and soil. This is mostly because it uses basic equipment and is adaptable to various ground conditions [7]. Because of its benefits, the NATM is frequently chosen. These benefits include the ability to instantly interface with tunnel support systems, modify support systems, and implement specific support configurations in accordance with the encountered ground types and adapt and change support types based on ground conditions [15]. However, experience demonstrates that it is crucial to understand its drawbacks and restrictions, which can call for adjustment because it might not work well in all geological settings [16]. Before face passage, a large portion of the ultimate stabilized settlement is induced. Only 3D analyses are able to replicate this sufficiently. Two-dimensional analyses are unable  
Figure 1: Recommended excavation pattern by [PERSON] (I, II, III, IV shows the sequence of excavation). to capture important details such as load transfer in the longitudinal direction caused by soil, acting. However, a suitable constitutive model is also crucial for an accurate displacement forecast. The most important single component examined in lowering induced settlements is the tunnel support lining. Even though the support is not yet fully operational, the displacements are smaller the closer the lining is to the face. The induced displacements are likewise significantly reduced by full activation with inverted closure [17]. In our further investigations, Figure 2 was utilized as the optimal method of staged excavation. The information at hand is used to modify the driving parameters in order to maximize tunneling efficiency or to assure safety [18]. This implies that there is a minimal difference in good rock mass between support following the Q-system and the support following the NATM. Significant variations exist in the selection of supports between the Q-system and the NATM due to swelling rock mass situations. We believe that the NATM permits more flexible support in low-quality rock mass classes. At each advancement phase, a prompt and specific response to the various rock mass behavior types can be provided using the NATM [19]. Controlling settlements caused by tunnel excavation is the primary problem with tunneling in urban contexts, which are usually characterized by a low overburden thickness and the presence of surface infrastructure. An accurate prediction of the displacement field caused by tunneling is the first step toward designing any protective measure that lessens the impact of the tunnel on nearby buildings. The application of a sophisticated soil constitutive model, along with high-quality experimental data and 3D finite element analysis, has been demonstrated to produce forward-looking estimates of the displacement field caused by a tunnel with a low overburden thickness that are correct [20]. Iran's Geological Organization states that Kahrizak silts completely blanket the land, just like in Tehran's north. Currently, fine-grained, untidy sediments from the current alluvium are faintly covering this silt. Because of tectonic forces, the region's soil is extremely compacted and very ancient. Additionally, the soil has a high over-consolidation ratio (OCR) due to pre-consolidation caused by the studies. Numerous deep underground canals in the field have collapsed and been damaged over time. Furthermore, the experiments demonstrate that the region is smooth and level despite the former rivers having been filled in with soil [21]. There is a discernible relationship between the design specifications and the prevailing stress conditions, as evidenced by the different priorities of the excavation methods based on the in situ stress levels [22]. This observation highlights the need in this specific area for a dynamic and adaptive approach to excavation design, which can be selected by numerical modeling.