Abstract: To investigate the big deformation control for soft rock tunnel construction with high geostress, we simulated the excavation of typical sections with big deformation by numerical approaches. Xiakou tunnel of Yichang-Badong Highway was taken as a case study. We adopted four construction techniques(method of ring cutting while preserving core soil, three-step method, two-sided pilot-hole method and CRD method) in the excavation simulation. By analyzing the tunnel deformation and plastic zone distribution respectively of these four techniques, we determined the stability of the surrounding rock, and analysed the advantages and shortcomings of the four methods. Results show that CRD method works best in terms of rock stability control. Finally, we verified the rationality of the construction technique by monitoring forces on the supporting structure and measuring the cumulative deformation and deformation rate. This research is an exploration on China’s soft rock tunnel construction with high geostress.

Key words: high geostress, soft rock tunnel, construction method, numerical analysis