Asymmetrical injections near tunnel linings

Uneven loading resulting from asymmetrical grout injections near a tunnel poses a risk of damaging tunnel linings. Counter-rotation of lining segments at joints concentrates the increase of lining stress and strain at the joints. The damage of lining joints will be more significant if the joints are not constructed properly. This paper discusses results from four centrifuge tests investigating the behaviour of a segmental lining when subjected to nearby asymmetrical injections. The tests were carried out in dense dry sand. Cavity expansion analytical solutions and finite element analysis are also presented to envisage the transfer of the injection pressure to the tunnel and the pattern of the lining deformation. Both analytical and numerical solutions show reasonable agreement with the observed tunnel lining deformation.