Discrete element method for modelling a fracture evolution of a roadway surrounding rock

A discrete element method for modelling a fracture evolution of a roadway surrounding rock, comprising following steps:

• S1:
• in a test roadway, observing deformation characteristics of the roadway and taking rock cores from coal seam and rock mass;
• recording deformation characteristics of the roadway surrounding rock, and monitoring distribution characteristics of fractures in roof and two ribs of the roadway;
• and taking rock cores from the roof and the coal seam, and recording RQD values of the roof rock cores and the coal seam rock cores;
• S2:
• separately making the obtained roof rock cores and the coal seam rock cores into standard intact rock, and carrying out experiments in mechanics to test an uniaxial compressive strength, a tensile strength, and an elastic modulus of the intact rock;
• and according to a functional relationship between a ratio of an elastic modulus of a rock mass to that of the intact rock and the RQD, and a functional relationship between an uniaxial compressive strength of the rock mass and that of the intact rock, determining the uniaxial compressive strength and the elastic modulus of the rock mass, wherein a tensile strength of the rock mass is 0.1 of its uniaxial compressive strength;
• S3:
• creating a calibration model by using a Trigon module in UDEC, wherein an average value of side lengths of triangular blocks in the calibration model is determined according to the distribution characteristics of fractures statistically analyzed in step S1;
• by using the uniaxial compressive strength, the tensile strength, and the elastic modulus of the rock mass calculated in step S2 as known characteristic values, performing an inversion with the calibration model to obtain parameters for a triangular block and parameters for a joint in the calibration model;
• and
• S4:
• creating a large-size numerical model with a field scale by using the UDEC, defining an area of study, and dividing the area of study into triangular blocks by using the Trigon module, wherein an average value of side lengths of the triangular blocks and the triangular block parameters are identical with those in the calibration model in step S3;
• forming rectangular blocks increasingly growing in length by division in areas outside the area of study;
• and based on the deformation characteristics of the roadway surrounding rock and the distribution characteristics of fractures that are observed in step S1, performing an inversion to obtain mechanical parameters of the rectangular blocks in the large-size numerical model.