Integrated identification method of rheological model of sandstone in Sanmenxia bauxite
(1. School of Resources and Environment Engineering, Wuhan University of Technology, Wuhan 430070, China;
2. School of Resources and Safety Engineering, Central South University, Changsha 410083, China;
3. School of Engineering and Materials Science, Queen Mary University of London, Mile End Road,
London E1 4NS, UK)
2. School of Resources and Safety Engineering, Central South University, Changsha 410083, China;
3. School of Engineering and Materials Science, Queen Mary University of London, Mile End Road,
London E1 4NS, UK)
Abstract: Based on the uniaxial compression creep experiments conducted on bauxite sandstone obtained from Sanmenxia, typical creep experiment curves were obtained. From the characteristics of strain component of creep curves, the creep strain is composed of instantaneous elastic strain, εme, instantaneous plastic strain, εmp, viscoelastic strain, εce, and viscoplastic strain, εcp. Based on the characteristics of instantaneous plastic strain, a new element of instantaneous plastic rheology was introduced, instantaneous plastic modulus was defined, and the modified Burgers model was established. Then identification of direct screening method in this model was completed. According to the mechanical properties of rheological elements, one- and three-dimensional creep equations in different stress levels were obtained. One-dimensional model parameters were identified by the method of least squares, and in the process of computation, Gauss-Newton iteration method was applied. Finally, by fitting the experimental curves, the correctness of direct method model was verified, then the examination of posterior exclusive method of the model was accomplished. The results showed that in the improved Burgers models, the rheological characteristics of sandstone are embodied properly, microscopic analysis of creep curves is also achieved, and the correctness of comprehensive identification method of rheological model is verified.
Key words: uniaxial compression creep experiments; instantaneous plastic rheological model element; improved Burgers model; direct screening method; posterior exclusive method