Theoretical optimization method of tunnel lining in fractured rock mass based on surrounding rock classification and Hoek-Brown criterion

Rationally accounting for the synergistic effects between tunnel lining and surrounding rock is crucial for accurately predicting reserved deformation in the design of fractured rock tunnels. This study employs a rock mass classification approach and the Hoek-Brown (H-B) strength criterion to evaluate the deformation behavior of surrounding rock, establishing a robust theoretical framework for calculating tunnel lining deformation considering the rock-lining interaction. A lining optimization approach is proposed, ensuring stress safety of the concrete lining and considering the displacement release rate of the surrounding rock. Case analysis validates the lining design's safety in the study section, identifying optimal parameters: support at 9 mm of tunnel wall deformation and a reduced lining thickness of 47 cm, achieving a 36.5% decrease from the initial design. The method enables the calculation of optimal support timing and lining thickness for various rock conditions, providing substantial reference for tunnel lining optimization.