Failure Process of Rock in Uniaxial Tension
The behavior of rock in tension is considered to be as important as in compression for designing underground structures, especially large ones. But few results of tensile tests have been reported.
The servo-controlled testing machine was used in this study, and uniaxial tension tests were conducted on six rocks (one granite, one andesite, one tuff and three sandstones). Complete stress-strain curves were successfully obtained, and compliance and irrecoverable strain were evaluated by unloading-reloading test. The main results can be summarized as follows;
1) Compliance increases through the whole process. But in the pre-failure
region, the increase rate is relatively slight. On the other hand, compliance in
the post-failure region increases rapidly with decrease of the load bearing
2) Irrecoverable strain is closely correlated with compliance change, i.e. with crack growth. The failure process of rock was discussed in detail based on the evaluation of compliance as well as irrecoverable strain.
3) The shape of stress-elastic strain curves in uniaxial tension tests are similar to those in uniaxial compression tests.
KEY WORDS: Rock, Uniaxial tension, Compliance, Elastic strain, Process zone