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.
The possibility of dynamic failure and deterioration of the sealing capacity of critically stressed rock due to the infiltration of a compressible non-wetting phase fluid is examined through laboratory experiments. Rock samples were regarded as critically stressed under normal faulting conditions, and was set up to mimic the conditions of the cap rock just above a reservoir layer. Two kinds of external stress conditions were applied to the sample, i.e., close to an isotropic stress condition and close to a critical condition for failure. Air in a gas accumulator was infiltrated into the sample from the bottom end. Axial and circumferential strains of the sample and air pressure at the inlet were monitored during the experiment. Experimental results showed that the sample under stress conditions close to the critical condition became more deformable, resulting in failure, while that under a hydrostatic condition did not deform significantly and behaved elastically. An increase in the permeability of the critically stressed sample was also suggested. Understanding an in-situ stress state and considering a possible progressive failure of the cap rock are considered to be important when evaluating sealing capacity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.