Damage mechanism of tunnels in the high-content salt rock stratum

The high-content salt rock stratum is a highly water-soluble, corrosive, and expansive stratum, and it is extremely difficult to construct tunnels in the stratum. The China-Laos cross-border railway friendship tunnel, which traverses the high-content salt rock stratum, sustained extremely serious damage during the construction. Therefore, studying the mechanisms by which the salt rock stratum tunnels are damaged is the key to ensuring the long-term service of the tunnel. In this paper, a comprehensive method system was used, such as on-site exploration, laboratory tests, and theoretical analysis, to identify the mechanisms by which the tunnels are damaged in the high-content salt rock stratum. Research has indicated that the main component of the rocks that surround the tunnel in the salt rock stratum is rock salt (NaCl and Na2SO4). Excavation in the salt rock stratum is prone to various catastrophes, such as the precipitation of salt crystals on the lining surface, the formation of a cavity at the bottom of the tunnel, cracking of the concrete lining, bulging and cracking of the inverted arch, and serious corrosion of the steel structure. Tunnels in salt rock stratum will undergo physical erosion and physicochemical erosion of the concrete lining in a water environment, and the precipitation of salt crystals and expansion will eventually damage the lining of the structure. Also, due to the accelerated corrosion effect of water and salt on the structure of the lining, cavities occur in the lining in a short time, and this results in a decrease of the bearing capacity.