CONSIDERATION OF THE RELATION BETWEEN THE GEOLOGICAL WEAK LAYER INCLUDING CRACKS AND THE TUNNEL INVERT HEAVING

Abstract

 We examined the effect of the geological structure outside the tunnel excavation cross-section on the tunnel deformation of at its intersection. A literature review confirmed that tunnel deformation increases in locations with fault fracture zones and weak layers with numerous geological cracks. After analyzing tunnel construction records for the relevant ground, it was confirmed that the displacement of the invert excavation surface increases in areas where weak layers with gentle slopes were present. Additionally, rock tests revealed a correlation between an increased slaking index in rocks with numerous cracks and an augmented blistering effect. Furthermore, numerical analysis demonstrated that the location and displacement of the tunnel defamation are influenced by the degree of intersection with the weak layer. It became evident that, to prevent tunnel deformation, especially invert heaving, it is crucial to identify the weak layer containing numerous cracks and confirm its continuity.