Non-linear elastic behavior and constitutive model of coal during compression and its application

Abstract: The widely distributed fracture system in coal results in significant non-linear characteristics in the compaction stage during the compression process. This stage occupies one-third of the entire compression process of coal, and is a key stage in the coal compression process. A non-linear elastic model based on the hyperbola was established to investigate the axial and lateral deformation of coal during the compaction stage in the present study. Four new modeling parameters were proposed: initial tangent modulus a, the reciprocal b of the axial strain at which the main stress difference tends to infinity, the initial Poisson’s ratio f, and the reciprocal D of the axial strain when the lateral strain tends to infinity. The method of determining the relevant parameters of the model was proposed by using the least square method. The effects of bedding and confining pressure on the non-linear mechanical behavior of coal were quantified. Bedding mainly affects the initial tangent modulus and initial Poisson’s ratio of coal. The increase of triaxial confining pressure will significantly weaken the non-linear deformation characteristics of coal. A non-linear elastic model was introduced into FLAC^3D, and the analysis results of the non-linear elastic model were compared with the traditional linear elastic model. The proposed model can better simulate the non-linear behavior of coal under compression. This model was applied in the analysis of coal tunnel displacement and shows potential for engineering application. Article Highlights: Significant non-linear characteristics exist in the compaction of coal.A non-linear elastic model based on the hyperbola is established.Bedding mainly affects the initial tangent modulus and initial Poisson’s ratio.The confining pressure significantly weaken the non-linear deformation.This model shows potential for engineering application.