Research and application of BAS-ESVM model for rheological parameter inversion of soft coal mass in roadway

The deformation of deep coal roadway has rheological characteristics.Accurate and efficient acquisition of rheological parameters of coal is an important basis for the study of rheological mechanism.Based on a typical case of rheological coal roadway, it is considered that the long-term deformation of the soft coal mass in the side wall of the roadway has two-stage rheological characteristics, i.e.the deceleration stage in the early stage and the constant velocity stage in the later stage.Obtaining the rheological parameters of the coal mass is of great significance for a further analysis of roadway instability.The artificial intelligence algorithms, Support Vector Machine(SVM) and Beetle Antennae Search Algorithm(BAS) are used.Aiming at the problem of selecting the kernel function parameter and penalty parameter C of SVM accurately, the improved evolutionary Support Vector Machine(ESVM) is composed to improve the learning and generalization ability of SVM by using the efficient optimization characteristics of BAS.Furthermore, the rheological model and elastic-plastic mechanical parameters of surrounding rock mass are defined.Based on the principle of orthogonal design, the dataset of rheological parameters of loose coal are constructed.A numerical model is established to model the deformation related to rheological parameters, and the calculated roadway displacement with time sequence is obtained.Then each group of rheological parameters and the displacement of sidewalls corresponding to time obtained by numerical calculation are taken as a group of samples to form a database.The above data are continuously learned through the ESVM model, and the best rheological parameters of coal mass are obtained by using BAS.Finally, the BAS-ESVM inversion model of coal rheological parameters is established.The obtained rheological parameters are verified by forward calculation.The results show that the calculated displacement is in good agreement with the measured values.The validity of the method and the correctness of the rheological parameters are proved.The method lays a parameter foundation for the study of the rheological mechanism of coal roadway.