Design of Cross Passage by 3D Numerical Simulation

When a project includes two parallel tunnels, cross passages linking both tunnels are normally constructed for safety reasons during tunnel exercise. Design and construction of the cross passages is a challenging issue in tunnelling design. Excavating cross passages through rock, soft ground, and mixed face conditions presents very different challenges often requiring intense ground reinforcing and grouting as well as handling groundwater creates additional difficulties. Excavation of the main tunnels, having a relatively larger dimension compared to the cross passages, usually involves in the use of full-face mechanized excavation. For cross passages, access is usually limited, excavation is implemented through traditional methods preceded by treatments if required. To evaluate the effect of cross passage excavation as well as different geometrical and geological parameters on induced displacements in the model, different scenarios were selected and afterwards by changing the geometrical data of main tunnels, cross passage, overburden and geotechnical parameters, a series of three-dimensional numerical analyses (FLAC 3D) were performed. The aim of this ongoing parametric study is to provide some abacuses that can be useful in engineering practice.