Abstract:
In order to investigate the influence of impact tendency on dynamic fracture characteristics of coal, cyclic loading and unloading tests with variable upper limit and dynamic and static type I dynamic fracture tests are carried out on three types of coal. The test results show that there is an approximate linear function relationship between strain energy
Un e and input energy
Un in in the cyclic loading and unloading process of three types of coal, and the unified expression formula is
Un e =1.032
Un in−5.536; the residual elastic energy index
CEF of the above three types of coal is 25.35, 30.34 and 33.26 kJ/m
3, respectively. The
KIC values of the static type I fracture toughness of the above three types of coal mass are respectively 0.249, 0.291 and 0.347 MPa•m
1/2 through the three-point bending test of the single-side notched beam, and the dynamic
KIC values under the impact load are respectively 0.344, 0.416, 0.527 MPa•m
1/2. With the increase of
CEF, the growth ratio of coal dynamic
KIC increases gradually, indicating that the impact tendency of coal will directly affect its dynamic fracture mechanical response. The greater the impact tendency of coal, the more the dynamic fracture parameters increase. In addition, with the increase of the impact tendency of coal, the fractal dimension of coal crushing under dynamic load increases, indicating that the fracture disintegration of coal under impact becomes more complex and the dynamic fracture response becomes more significant.