Based on the observed data of the creep deformation of surrounding rock and creep constitutive model for weak rock mass

back analysis of elastoplastic parameters of surrounding rock for roadway in mudstone is done. The rock mechanical parameters are obtained by back analysis; the obtained elastic modulus is 2.0 GPa; cohesive force is 1.31 MPa and angle of internal friction is 24º. The range analysis results for the mean values of inversion parameters show that the size of the range can be used to judge the sensitivity of rock mechanical parameters. For the creep character

cohesive force is the first influence factor; the second one is the angle of internal friction and the third one is the elastic modulus. Then

deformation of the surrounding rock is calculated using the basic mechanical parameters obtained by back analysis; the creep displacement increment in each observed point is calculated; and they are in good agreement with the measured values. These results show that the actual situation of roadway is reflected by the deduced rock mechanical parameters. Finally

the displacements and plastic zone range of roadway are predicted.