Fig 1.
Rock testing machine and rock samples:(a)Rock testing machine,(b)rock samples.
Fig 2.
The triaxial stress-strain curves of rock under different confining pressures.
Fig 3.
The triaxial creep curves of rock under different confining pressures:(a)the stress-strain curve of confining pressure 5MPa,(b)the stress-strain curve of confining pressure 10 MPa,(c)the stress-strain curve of confining pressure 15 MPa,(d)the stress-strain curve of confining pressure 20 MPa,(e)instantaneous strain,(f)creep deformation.
Fig 4.
Isochronous stress-strain curves of rock under different confining pressures:(a)the isochronous stress-strain curve of confining pressure 5MPa,(b)the isochronous stress-strain curve of confining pressure 10 MPa,(c)the isochronous stress-strain curve of confining pressure 15 MPa,(d)the isochronous stress-strain curve of confining pressure 20 MPa.
Fig 5.
The determination method of time t1.
Table 1.
Creep model parameter values of roadway surrounding rock considering the combined effect of hardening effect and damage effect.
Fig 6.
Comparison of sandstone creep model curves considering hardening and damage effects:(a)fitting curve of confining pressure 5MPa,(b)fitting curve of confining pressure 10 MPa,(c)fitting curve of confining pressure 15 MPa,(d)fitting curve of confining pressure 20 MPa.
Fig 7.
Comparison between Nishihara model and the model curve:(a)comparison curve of confining pressure 5MPa,(b)comparison curve of confining pressure 10 MPa,(c)comparison curve of confining pressure 15 MPa,(d)comparison curve of confining pressure 20 MPa.
Fig 8.
The comparison between different types of rock test curves and creep model curves in the literature:(a) confining pressure 10 MPa,(b) confining pressure 15 MPa.