ESTIMATION OF MOBILIZED COHESION AROUND UNDERGROUND OPENINGS

Based on the field data obtained from 12 Indian and several NGI case h istories, a semi-empirical relation has been proposed in this paper fo r determination of ''mobilised'' cohesion around underground openings. It has been found that mobilisation of cohesion takes place at higher values around underground openings than the values previously suggest ed and the values obtained from block shear tests. A strength enhancem ent factor has been suggested which is to be multiplied with the cohes ion parameter obtained from block shear tests for practical applicatio n. This apparent strength enhancement may be attributed to anisotropy in strength, statistical variation in strength and confining condition s around tunnels. (C) 1997 Elsevier Science Ltd.