Effects of dilatancy and yield criteria on displacements around tunnels

Abstract

Analytical elastoplastic solutions for stresses and displacements around a circular opening have been developed, using two different yield criteria and a nonassociated flow rule. The effects of dilatancy and postpeak decrease in strength are included in these solutions. It is shown that the two different yield criteria lead to practically identical results, while the dilatancy angle plays an important role in controlling radial displacement. Four case histories, one in soft fractured rock and three in a heavily overconsolidated stiff clay, are analyzed. The calculated radial displacements along the crown line are consistent with results of field measurements. Key words: tunnels, elastoplastic analysis, stress, strain, dilatancy, yield criteria, postpeak strength, nonassociated flow rule, soft rock, stiff clay.