ABSTRACT
The Greater Cairo Metro, a major project of underground railway in Cairo city, Egypt, is presently under construction. During the construction of the Greater Cairo Metro line no. 2 (Shubra El-kheima – Mubarak), problems were encountered related to the stability of the soil around the tunnel. Settlement and water seepage occurred during the tunnel excavation. Serious problem was expected to occur where the metro tunnel passed under the sewage tunnel. To alleviate the potential problem, grouting was applied beneath the lining of the sewage tunnel. This paper presents the results from a study of the effects of the grouting on soil behavior and the deformation of the sewage tunnel. The engineering solution by grouting and its effectiveness on the problems of settlement and radial displacement are discussed. The crossing between the sewage tunnel and the metro tunnel is modeled using shell elements. The model is loaded by the overburden pressure while the subgrade reaction of the soil is represented by the elastic support at the nodes along the lower half of the sewage tunnel. Numerical analyses have been carried out to study the effectiveness of grouting on the behavior and performance of the tunnel system. The effects of compressional modulus of the soil and the depth of the tunnel on the vertical settlement and the radial displacement of the sewage tunnel have been studied. Comparisons of the effects of the grouting procedures are discussed. The results show the effect of grouting on reducing the settlement and the radial displacement of the sewage tunnel. The numerical results correlate well with the field measurements recorded by the National Authority of Tunnel (NAT).
