关键词: 冰煤, 断裂韧度, 裂纹深度

Abstract: Coal is always frozen into block with water in transportation for the purpose of being fixed up and not burned. As a sort of multiple components and a granule aggregation in dispersed state, frozen coal behaves similar to frozen soil. On the basis of its unique ice-cementation effect and the existent of non-frozen water that varies with dynamical balance state between the frameworks of mineral granule, the mechanical behaviour of frozen coal is more complex than usual incompact medium, dependent on load, vibration period and temperature. In order to make it easy to unpack frozen coal, people prefabricate some cracks on it before transportation. In this thesis, experimental study of fracture toughness of frozen coal at low temperature is presented. Three-point bending tests are conducted on frozen coal so as to determine its fracture toughness K_IC under various crack length. Sample dimension must meet three essential conditions: plane strain condition, linear elasticity condition and ligament size condition. After the tests, K_IC was calculated from the test data, which should be taken take into account with the three essential conditions to validate the validity of the test. The test results show that the value of K_IC of frozen coal decreases with shortening the crack length. Thus the crack should be prefabricated deep customarily. But due to vibration action from the carriage, the crack may be getting deeper. So under vibration action, the depth of crack should be prefabricated equal to the reality. Sample preparing, test equipment construction, calculation formula of K_IC, of plastic area in crack peak, phenomena of inactivation and development of crack are also discussed.

Key words: frozen coal, fracture toughness, crack lengty