ABSTRACT
Based on a tunnel project in a European country, this paper re-estimates the rock mass classification comprehensively through the method of RMR, Q, and GSI. After analysis by the RMR system, the quality of surrounding rock in the fracture zone and at the tunnel entrance and exit is Class V, and it is also possible for parts of the tunnel area to reach Class III. Through the Q system, the surrounding rock is around level E (0.1 < Q < 0.5） and level F (0.01 < Q < 0.1), mainly level F (extremely poor), equal to Class V by the RMR system. After estimation by the GSI system, the surrounding rock is around Class VIII, X, and XI, and VI, VII in certain sections. It is considered that the employer's classification is reasonable, while the designer's classification conclusion has some potential risk due to the higher parameters adopted and cannot match the actual geological conditions of the tunnel. The “low price winning concept” can greatly benefit the bidding competitiveness, while the over-optimization of the design will certainly increase the difficulty of design approval, squeeze the profit margin of the company, and will bring plenty of risks in terms of cost and safety issues during implementation.
