Analysis of regular disease process of loess tunnel support structure based on field investigation and testing

In the referred loess tunnel, there was no groundwater during the preliminary investigation phase, but there were water seepage, cracks and other hazard-related problems during the construction. Based on investigation of the relationship between the tunnel and the surrounding water system, this paper developed a three-dimensional terrain model and revealed the relationship between the groundwater and the tunnel in combination with the drilling and geophysical data. This study confirmed that there was a close correlation between tunnel structural cracking and water seepage as well as groundwater level variations. Even with large tunnel depth (i.e., 40–116 m), the soil fissures can still provide a fast infiltration channel for surface water and upper stagnant water, leading to a rise in the groundwater level and causing regular hazards of the tunnel. These problems can be solved by improving the design, strengthening construction control and drainage in the tunnel site.