Structural behaviour of reinforced concrete tunnel lining under earth pressure

The stability of tunnel support is mainly a function of the induced deformation and stresses from ground movement. The role of the support system is to control tunnel deformation within an allowable limit. In such circumstances, the design of support system is generally based on the ground lining interaction. Two parallel approaches are adopted for this paper. One is the field investigation which consists mainly of collecting data about the proposed design of tunnel crossing Ismailia canal in Cairo as well as the physical and mechanical properties of different layers around it. This tunnel is a part from line No. 1 in Cairo metro-network which will be a new line connecting Shubra EL-Kheima station in the north with Giza station in the south-west of Cairo. The other approach is the two-dimensional finite element analysis which is applied to give better understanding for the structural behaviour of the R.C. lining under earth pressures. Attention is focused on the effect of the stiffness of the plain concrete backfill(foundation stiffness) in tunnel base on tunnel stability. Different lining thicknesses and its properties as well as vertical and horizontal field stresses are taken into consideration. The critical loads P cr for different lining thicknesses and foundation stiffnesses are determined.