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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

The principal aim of this paper is to analyze the impact of rubber pad systems on levels of vibrations and values of stresses and deformations induced in the subway tunnel segments. Thus, the 3D model has been selected to be isotropically simulated in the ANSYS program to conduct a finite element analysis. Therefore, the proposed track system in the tunnel of line 4 of the Greater Cairo Metro has been selected as an analytical and simulation case study. The impact of using eight different values for the stiffness of the rubber pad system in the case of a single tunnel has been analyzed. The results showed that levels of vibrations are significantly affected and are in logarithmic correlation with the stiffness. Also, the impact of the stiffness on the deformations and stresses are determined as well as mathematical models connecting the different parameters have been introduced.

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