Undrained creep behaviour of Mexico City Clay

This technical note presents the results of a number of undrained triaxial creep tests on Mexico City Clay, performed under different deviatoric stress levels and at different consolidation pressures. Tests were performed using a specially designed triaxial apparatus that minimises friction in the load application system. For the undrained tests, pore-water pressures were monitored to track the evolution of the effective stress state during the tests. Conventional strain-controlled, consolidated undrained triaxial tests were also performed to serve as a reference for interpreting the observed behaviour. It is shown that creep failure occurs when the effective stress state reaches the strength envelope defined by conventional monotonic tests.