The effect of an existing tunnel and a newly excavated tunnel on ground loss beneath sand slope-3D numerical study

Authors

Ashraf Nazir, tanta university ,faculty of engineeringFollow
ahmed nasr, tanta university,faculty of enginneringFollow
asmaa saeed, Tanta University - Faculty of EngineeringFollow

Abstract

Abstract- Most researchers perform their numerical models for tunnels by modeling perfectly horizontal ground surfaces above the tunnels. The prediction of surface settlement of a sandy slope due to the interaction mechanism between the slope and the tunnels is one of the critical problems in urban areas. As a result, in this work, a numerical analysis using PLAXIS 3D TUNNEL has been performed to investigate the effect of tunnel excavation on the deformation of a shallow sandy slope, and empirically by the Herzog method. The study also assesses the influence of parameters on slope deformation that have not been covered in the previous studies, namely the tunnel cover depth, the tunnel configuration, and the new tunnel advancement beside an existing one. For shallow and deep tunnels, the pattern of the slope settlement surface trough after excavating the new one beside an existing one becomes wider and larger compared with the case of the existing tunnel only. The maximum surface settlement is noticed for the configuration with a closed tunnel (S_x/D = 1.5-2) and kept constant after horizontal spacing (S_x/D=5). The driving of the new tunnel below and inclined causes a significant increase in the slope deformation by about 100%, compared to the case of the existing tunnel only. The maximum surface displacements increased, compared to the single case (existing tunnel only), by about 80% after the first 10m advancement of the second tunnel. It is expected that the knowledge of the plastic zone distribution will help in the first liner strengthening process as well as understanding the extent of deformations at different positions of a new tunnel. The results can help designers to control the surface settlement of a sandy slope caused by twin tunnels.

Keywords:. Surface Displacements, Tunnel Depth, sandy slope, Spacing and rotation, Herzog method.

Recommended Citation

Nazir, Ashraf; nasr, ahmed; and saeed, asmaa (2023) "The effect of an existing tunnel and a newly excavated tunnel on ground loss beneath sand slope-3D numerical study," Journal of Engineering Research: Vol. 7: Iss. 6, Article 1.
Available at: https://digitalcommons.aaru.edu.jo/erjeng/vol7/iss6/1