Simulation experiment on bearing mechanical properties of gangue aggregate

In order to explore the bearing characteristics and fracture evolution law of gangue aggregate, a hydraulic servo rock mechanics test system and a broken gangue compaction device are used to conduct a compaction test of crushed gangue aggregate. The test is under the conditions of different gangue particle sizes(0-5,5-10,10-15,15-20,20-25 and 25-30 mm),different axial stresses(2.5,5.0,7.5 and 10.0 MPa) and different loading rates(0.05,0.10,0.50 and 1.00 mm/s). Also, the effect of various factors on the compression deformation and fractal characteristics of gangue aggregate is studied. A particle flow model considering gangue shape and particle size distribution is established using the PFC⁽3 D) numerical software, the laws of energy dissipation and force chain evolution in the bearing process of gangue aggregate are discussed, and the effect mechanism on the compaction mechanical properties of gangue aggregate by the particle shape and particle size gradation are revealed. The test results show that the compression deformation of gangue aggregate can be divided into three stages: pore compaction, structural adjustment and elastic-plastic deformation. With the gradual increase of axial stress, the skeleton of large particles of gangue aggregate is destroyed, the sliding displacement of medium particles and small particles fill the pores. The contact mode between particles changes from acute angle contact to obtuse angle or spherical contact. Under different loading rates, the axial stress and strain of gangue aggregate shows a power function distribution, and the axial stress and loading rate demonstrate a logarithmic function relationship with the fractal dimension of broken gangue. Under the same load, large-size gangue is easy to crush. Gangue particles overcome deformation and consume friction energy, which is conducive to strengthening the overall friction effect. The length of force chain of gangue aggregate gradually increases with the increase of load, the coverage gradually increases, and the high stress range gradually expands from top to bottom. With the increase of external load, the mesh structure of gangue particles breaks and fails, and the rock blocks slide, shift and reorganize. Small particle size gangue particles can weaken the fracture failure.