Research on Mechanical Properties and Damage Constitutive Model of Water-Bearing Coal

Abstract

Many water-related problems are confronted in coal mining, and the mechanical properties of coal inevitably deteriorate due to water–rock interactions. Therefore, it is necessary to study the macroscopic mechanical properties and damage constitutive model of water-bearing coal for safe mining. The uniaxial compression tests of raw coal samples with five moisture contents under four loading rates were carried out. Based on the test, the Drucker–Prager criterion is introduced to describe the failure law of micro-elements; assuming that the strength of micro-elements obeys a two-parameter Weibull distribution, a three-stage damage constitutive model is established. The model, existing model, and test curves were compared, and four indicators were introduced to evaluate the fitting effect. The results demonstrate that the stress–strain curve has a near horizontal step before the elastic stage, and its length is positively correlated with the moisture content ω. With the increase in ω, the peak strain increases linearly, and the compressive strength and Young’s modulus first increase and then decrease. The loading rate does not change the type of the fitting function between the mechanical parameters and ω. The three-stage model is more universal and can better fit the full stress–strain curve of water-bearing coal under uniaxial compression.