ABSTRACT

In conventional tunnelling ground reinforcement using bolts is a very popular measure for stabilizing the face because of its relatively low cost, its great flexibility and its adaptability to local geological conditions. The face reinforcement, as almost all geotechnical auxiliary measures in tunnelling, is carried out ahead of the tunnel face intermittently with the excavation, thus slowing down construction progress considerably. In view of its implications for construction time and cost, face reinforcement needs a particularly careful design. In addition to experience and engineering judgment, calculations are indispensable. The paper presents a computational tool for the design of bolt reinforcement that can be applied to heterogeneous, layered ground as well as to reinforcement layouts that are arbitrary in terms of the spacing, length, longitudinal overlapping and installation sequence of the bolts. Several examples are presented in order to discuss possible optimizations of the bolt reinforcement.