RATIONAL DESIGN OF TUNNEL SUPPORTS. A MODEL STUDY OF SPILING REINFORCEMENT IN UNDERGROUND OPENINGS
In an effort to contribute to the development of a rational design approach in the use of spiling reinforcement in underground construction, the mechanisms of spiling reinforcement were investigated through physical and numerical models, and the contribution of spiling as an immediate stabilization as well as its contribution to the permanent stabilization of a circular tunnel were ascertained. The rock mass characteristics for grounds where spiling had found application were assessed from case histories and other investigations. Physical model laws were derived. On the basis of the rock mass characteristics, a suitable modeling material was developed. A model test chamber and instrumentation system were designed, and physical model tests with and without spiling were performed. A numerical model was developed to aid in the interpretation of the physical model results. The overall response related to immediate stabilization is illustrated by comparing stand-up time: without spiling reinforcement, the time was less than 400 minutes; with reinforcement, the opening was stabilized. A strong case is presented for pre-reinforcement as constrasted with reinforcement after excavation. The use of spiling reinforcement or pre-reinforcement as the sole means of permanently stabilizing an otherwise unstable opening was also demonstrated. It is concluded that spiling reinforcement can stabilize a rock mass effectively as it reduced deformations and thereby deterioration due to strain softening and reduction in the inherent available rock mass strength; provides rock mass confinement, leading to increased available strength-this is very effective near the opening on account of the high friction angles associated with low confinement; and maintains rock arch continuity allowing for increased tangential stress in the immediate vicinity of the opening.
University of California, BerkeleyDepartment of Civil and Environmental Engineering
Berkeley, CA USA 94720-1710
- Corbin, G E
- Brekke, T L
- Publication Date: 1975-2
- Features: Figures; References; Tables;
- Pagination: 258 p.
- TRT Terms: Case studies; Instrumentation; Mass; Mathematical models; Reinforcement (Engineering); Rocks; Shear stress; Softening point; Soil stabilization; Tunneling; Underground structures
- Uncontrolled Terms: Confinement; Model tests; Models; Rock mass; Stabilization
- Old TRIS Terms: Tangential stress
- Subject Areas: Bridges and other structures; Geotechnology; Highways;
- Accession Number: 00126843
- Record Type: Publication
- Report/Paper Numbers: MRD-2-75 Tech. Rpt.
- Contract Numbers: DACW-45-74-C-0026
- Files: TRIS
- Created Date: Nov 5 1975 12:00AM