Numerical Modeling of Soil-Tunnel Interaction under New Surface Load

Document Type : Original Article

Authors

Egyptian Armed Forces.

Abstract

El-Azhar road tunnels, a major project of underground structures in Cairo, Egypt,
were constructed by the tunneling boring machine (TBM). During construction of a proposed
building over the existing El-Azhar road tunnels, Geotechnical challenges are expected to
occur. An example of these challenges arises when the proposed building is constructed over
the existing southern road tunnel. However, the serious damage in the road tunnel liners is
predicted and the maximum radial displacement of the road tunnel is also computed. The
allowable radial displacement of the road tunnel liners when the proposed building is
constructed over the road tunnels should be checked within the allowable limit of 10 mm set
by the Egyptian Standards.
In the present study, the prediction of the impact of the proposed building construction on El-
Azhar tunnels is highlighted and a model is proposed to study the soil structure interaction
using a 2-D model of the proposed building on EI-Azhar tunnels. The study is conducted
using Finite Element Method. The constitutive model for this analysis contains elasto-plastic
materials. A yielding function of the Mohr-Coulomb type and a plastic potential function of
the Drucker-Prager type are employed. A linear constitutive model is employed to represent
the tunnel liners.
The effects are expressed in terms of settlement and radial deformation in the road tunnels.
The study includes the prediction of the settlement, the relative movements, and the lining
stress under different loading steps. The description of the used model, the output results, and
the final conclusion are presented in this paper.

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