Abstract: To investigate the impact of factors such as waterstops, interface agents, and interface roughness on the impermeability of tunnel lining construction joints, and to enhance the water pressure resistance of linings in water-rich tunnels, the waterproof structure of tunnel lining construction joints is examined to identify the crucial influencing factors of their impermeability performance. The research includes designing and performing indoor impermeability tests on 162 specimens to conduct a sensitivity analysis of various factors and elucidate their mechanisms of action. The findings demonstrate that: (1) Construction joints with pouring intervals exceeding 7 days exhibit a decrease in concrete impermeability by 2 to 3 orders of magnitude, influenced by the impermeability at the interface between the new and existing concrete, and between the waterstop and concrete. (2) Reducing the pouring interval and applying interface agents effectively lower the permeability coefficient at the interface between new and existing concrete. (3) Enhancing the roughness of the construction joint interface through chiseling does not significantly improve impermeability; excessive chiseling, in fact, diminishes it. (4) With a pouring interval of 7 days and no chiseling, the average relative permeability coefficient at the interface between the rubber waterstop and concrete is 47.5% of that at the interface between new and existing concrete, indicating superior impermeability in construction joints. (5) The permeability coefficient at the interface between steel plate waterstops and concrete is approximately equal to that between new and existing concrete, functioning to extend the seepage path length.

Key words: tunnel lining, construction joint, impermeability, waterstop, interface agent, impermeability test