Research on the uniqueness of displacements back analysis for viscoelastic rock masses based on the Kelvin-Voigt model

In geotechnical engineering, accurate mechanical parameters of rock mass are very important for the construction and maintenance of engineering projects. Compared with the methods of obtaining parameters such as in-situ test, laboratory test and numerical simulation, the displacements back analysis method of rock mass has the characteristics of convenient operation, less difficulty in obtaining conditions and accurate data. The uniqueness of the back analysis results is an important factor affecting the success of the displacements back analysis. In order to study the uniqueness of displacements back analysis results, the displacement analytical solution of viscoelastic rock mass conforming to Kelvin-Voigt model in circular roadway is derived by using Laplace transform and creep compliance method, and the influence of known parameters on the uniqueness of viscoelastic rock mass back analysis is studied by using parameter variability criterion. The results show that under any conditions, it is impossible to uniquely invert all six parameters, and it is possible to uniquely invert other parameters when at least two parameters are known. The probability that the in-situ stress component is uniquely inverted is the largest. The identifiability of elastic modulus, Poisson’s ratio and viscosity coefficient varies according to different control conditions, and the identifiability of parameters increases with the increase of the number of known parameters. Whether the ground stress is 0 has a significant impact on the uniqueness of the inversion results. The calculation of engineering examples shows that the research results have important guiding significance for the back analysis and calculation of rock mass parameters.