Research on Rock Bolt Reinforcement and Integral Lined Tunnels
Abstract
Two approaches to finite element analysis of the effects of rock joints and fractures on underground unlined, lined, or reinforced tunnel openings are considered. First, a three-dimensional ubiquitous joint analysis is described and applied to tunnel design. Although this approach allows an estimate of the weakening effect of closely spaced joint sets, it is based on the assumption that the existence of a joint does not alter the stress distribution significantly. Since this may not always be a satisfactory assumption and because it may sometimes be desirable to model the action of individual joints occurring in determined locations, a new rock joint representation is developed and a joint stiffness analysis applied to a series of basic problems. The different types of rock joints and their relative significance are discussed and a classification system based on shear strength of the joint, stiffness perpendicular to the joint and tangential stiffness of the joint is suggested. Using a finite element axisymmetric program, states of stress in the rock due to single and multiple rock bolt installation are examined and iso-stress maps of the triaxial compression zones are shown. States of stress in the vicinity of the rock bolt anchor and bearing plate are investigated. The effectiveness of a single rock bolt installation to strengthen rock joints of various orientations is investigated. In a very preliminary study, the theory of a layered orthographic shell was coded using a finite element plane strain representation. An evaluation of the load resisting capability of various tunnel linings incorporating different types of stiffeners was made. Further analytical work is recommended.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1967
- Accession Number
- ADA363465
Entities
People
- Richard E. Goodman
Organizations
- United States Army Corps of Engineers