Dakui tunnel is a highway tunnel on the Yanling-Rucheng expressway; its geological condition is very complicated. After the tunnel construction

the first support deformed seriously; the steel support was bent; and the sinkage exceeded the construction limit seriously. Combining the in-situ measurement results with the ground penetrating radar (GPR) scanning results

the reason for serious tunnel deformation after first support in watery and weak zone is analyzed based on the water gushing feature

geological condition and the construction method. Then

the support design and construction organization scheme for tunnel face and segments with failure support are studied. And three treatment measures are proposed as follows: 1) controlling the water gushing; 2) backfilling with back pressure and reinforcing the surrounding rock; 3) optimizing the construction method. According to the measurement results

it is shown that the three above treatment measures are good for controlling the tunnel deformation and ensuring the safety of tunnel construction under complicated geological condition. This research plays an important guiding role and provides a significant reference value for tunnel construction in watery and weak stratum.