Field monitoring and numerical analysis of ground deformation induced by tunnelling beneath an existing tunnel

Abstract

The main challenge of implementing and constructing a new tunnel is to monitor and mitigate ground surface disturbances that may affect existing structures. This paper analyses the soil deformations induced by tunnelling under an existing tunnel and the effect of these deformations on the existing tunnel. Both field data and numerical modelling are included in this study. Numerical modelling based on the finite element method is established to simulate the tunnelling process and the technique used in the shield machine. The model is applied to the case study of the intersection between metro line 3 tunnel underneath the existing main sewage tunnel in Cairo. Settlement of the existing tunnel and the ground surface associated with the new excavation of the new metro line 3 tunnel are monitored. The numerical model is verified with the records from the field data and then used to conduct a comprehensive parametric study to investigate the effect of tunnel orientation angle, clear distance between tunnels, soil properties, and grouting around the tunnels, on ground deformation. The analysis considers the nonlinearity of the soil, the construction stages, the grouting around the tunnel, and the shield operating parameters. Findings quantify the importance of the studied parameters on the deformation and stresses of the existing tunnel and

Simulation of Surface Settlement Induced by Parallel Mechanised Tunnelling

“…Most studies [3,27] investigated these issues for single tunnels; however, limited studies are available for twin tunnels using earth pressure balance (EPB) shield machines. In the recent numerical tunnelling analysis carried out by Islam and Iskander [28], the effect of geometric parameters and construction sequence on the SS was investigated using MIDAS GTS NX software 2021 (v1.1).…”

“…The interplay between the tunnel lining and the nearby soil can trigger certain adaptations and shifts in the ground, indirectly resulting in surface settlement. Numerous studies [3,24] have demonstrated that face pressure and grouting pressure are the two important contributors to the SS caused by mechanised tunnelling. Hence, in this study, these two parameters were considered to be part of the finite element analysis.…”

“…Different conditions of face pressure result in different SS scenarios. Several studies have found that increasing face pressure causes a decrease in settlement [3,57]. A different ideal scenario for the face pressure that affects the SS is illustrated in Figure 8.…”

“…Several problems can be encountered during tunnel excavations, such as tunnel face instability, excessive wear of the cutter head, and excessive surface settlement (SS) [1,2]. Among them, SS induced by mechanised tunnelling is still one of the common issues in tunnel construction [3,4]. The excessive SS during and after tunnelling projects has an adverse impact on the existing structures.…”

Effect of Undercrossing Shield Tunnels Excavation on Existing Rectangular Pipe-Jacking Tunnels

“…Xu et al [40] studied the influence of new tunnels with different excavation sequences and grouting reinforcement ranges on existing pipelines above. Using the finite element model, Nasser et al [41] analyzed the ground deformation caused by a new tunnel undercrossing an existing tunnel, and obtained some parameters to control the deformation. Xue and Zhang [42] studied the support pressure of the excavation face when a new tunnel crossed beneath an existing tunnel, and analyzed its influence on the surface settlement and segment deformation.…”