Model test and trial construction of polyurea spray as the spalling prevention method of tunnel lining concrete

Abstract: Preventing concrete spalling is very important in tunnel maintenance because spalling in railway tunnels may causes a direct safety hazard to train operations. This paper deals with the applicability of sprayed polyurea as the spalling prevention method of tunnel lining concrete. The model test and trial construction have been carried out. In the model test, vertical displacement was applied at the arch crown of the model tunnel lining. When displacement reached 30mm, the bending compressive fracture occurred at shoulder part of the lining, on the other hand spalling of concrete lining did not occur because the polyurea covered exfoliated concrete. From the model test, great spalling prevention effect was confirmed. In the trial construction in an actual tunnel, 3 kinds of surface preparation before polyurea spray are tried and evaluated the difference of bond strength and construction time.