Theoretical and experimental study on equivalent nonlinear Burgers model for soften rockmass

The classic Burgers creep model only combined with several liner basic cells can hardly describe the accelerating creep stage of rock material, while the creep attribute of the weak rock is very remarkable. Based on creep damage and hardening mechanisms, the cell of Maxwell was replaced with a nonlinear softening spring, while the Kelvin was replaced with a nonlinear hardening damper, and the two cells were acted in series. An equivalent nonlinear Burgers creep model was built and the corresponding creep equations were deduced. In addition, an experimental study was conducted by collecting rock samples from practical engineering. According to the results, some programs were developed to deal with the test data and the model corresponding parameters were also fitted. Hereby, a theoretical creep curve was achieved and then compared with the creep testing curves. It was shown that the equivalent nonlinear Burgers creep model was felicitous to characterize the creep behavior law of the weak rock.