Study on tunnel planning of weakly cemented sedimentary rock of tertiary period: A study on tunnel disaster prevention in construction (2)

Abstract

In this paper, rock classification and supporting patterns of tunneling were proposed for weakly cemented Tertiary sedimentary rocks. A tunnel was planned in the Yeonghae area of North Gyeongsang Province, where the weak rock is dominantly spreading; the shear and deformation characteristics were analyzed using field and laboratory test results, and case studies on design of nearby tunnels and from the literature were extensively reviewed. The majority of bedrocks that tunnels would encounter were mudstone and mudstone-breccia, whose compressive strengths were measured at between 3.1 and 14.8 MPa; they slaked within 18 hours using jar slake test. Conventional rock classifications such as RMR and Q-system are inappropriate to apply to these types of rocks, which are highly susceptible to water, because the conventional classifications were developed mainly based on conditions of discontinuities. The existing rock has few discontinuities but contains high risks during construction. Therefore, an alternative rock classification system considering the seismic velocity (Vp), uniaxial compressive strength, and strength ratio is required for weakly cemented Tertiary sedimentary rocks. © 2020 The Korean Society for Railway. All rights reserved.