EN
EN
**Behro Comprehensive Consulting Engineers**
**Davood Parsapour, Dariush Mohammadi, Kourosh Shahriyar**
Journal of Mining and Environment (JME)
**August 6, 2021**
**Tunnel excavation in urban areas is inherently associated with numerous uncertainties.** If these factors are not adequately considered during the analysis and design stages, they can lead to serious hazards and unforeseen events during construction. One of the most significant sources of uncertainty is the presence of various obstacles along the excavation alignment. These obstacles may include **urban utilities, surface and subsurface structures, channels, wells, tanks, and unknown voids**, all of which can directly affect the tunnel construction process. **Tehran Metro Line 7** is no exception and has faced similar challenges.
This study investigates the effects of **wells and unknown subsurface voids** located within the zone of influence of tunnels excavated using **Earth Pressure Balance Machines (EPBMs)**. The main novelty of the research lies in recognizing **wells and underground voids as obstacles with a risk level comparable to that posed by structures adjacent to the tunnel**, an issue that adds complexity to both tunnel design and construction.
To analyze this issue, **three-dimensional numerical modelling based on the Finite Difference Method (FDM)** was employed, along with a series of **parametric studies** considering the geometric configuration of the wells and subsurface voids and their positions relative to the tunnel under **alluvial ground conditions**. The results indicate that the greatest **disturbance and instability** occur in the vicinity of the well and tunnel, with the strongest interaction between the two taking place **ahead of the tunnel face**. The findings also show that the **most critical ground settlement condition** occurs when a well or unknown subsurface void is located **directly in front of the tunnel face**.
Ultimately, the study demonstrates that **ground behavior in response to EPBM tunnelling** varies across different zones of the machine, including **ahead of the tunnel face, the cutterhead, the shield, and the segmental lining**, with each section having a distinct influence on ground response. These findings can provide valuable guidance for **more informed decision-making during the design and construction of urban tunnels**.
