Seepage characteristics of a new polymer-based sprayed membrane waterproof-drainage system for tunnels and its applicable scope

In the traditional composite lining of tunnels, there are cavities between the waterproof board and the primary support, which are prone to water channeling. Once there are local defects in the waterproof board, it is highly likely to cause water leakage in the tunnel, posing a menace to the safe running of the tunnel. Relatively speaking, the sprayed waterproofing materials have the characteristic of being closely attached to the primary support and secondary lining, which can effectively avoid the occurrence of water channeling. However, there is still little research on the sprayed membrane waterproof-drainage systems and its applicable scope. To address this issue, this paper proposes a new type of waterproof-drainage system based on polymer-based sprayed membrane, and a numerical calculation is adopted to conduct seepage characteristic analysis. Finally, the applicable scope of water environment is determined. The research shows that: the distribution characteristics of the longitudinal water pressure in the tunnel with the new sprayed membrane drainage scheme are "wavy". With the increase of the permeability coefficient of the surrounding rock and the water head height, the maximum water pressure outside the lining is steadily increased. In actual engineering projects, according to the permeability coefficient and the water head height, by referring to the applicable water environment scope diagram, the corresponding area can be identified and a primary waterproof-drainage scheme can be provided.