Study On Rockburst Initiation And Failure Propagation

Rockburst is a worldwide serious natural disaster encountered in coal mining and rock engineering. It has been a scientific difficulty which should be solved urgently in the field of mining engineering and rock mechanics. The dissertation has done a systematic study on the rockburst initiation and failure propagation.The rockburst initiation criterion have been studied: The Energy Criterion and Disturbance Criterion are put forward. The analytical solutions for rockbursts occurring at the coal pillar, mining working face and in the circular roadway are derived. A new index for the possibility of a rockburst occurrence, the ratio between the elasticity modulus E and the descending modulus X of the rock-coal mass, namely E/λ , is suggested. The relations have been determined between the critical depth of softening zone, the critical load, the critical mining depth, the energy release after a rockburst initiation and E/λ. Resistance Zone is suggested and the relation between its size and E/λ is derived. This part of research results provides a sound mechanical foundation for rockburst prediction and treatment.The deformation-failure propagation after rockburst initiation have been studied: It has been found that the deformation of the coal-rock mass localizes after the rockburst starts. The paper suggests that the deformation-failure process of the coal-rock mass be analyzed by studying the localization. Controlled by the great stiffness of the testing machine and the small loading rate after rockburst initiation ,traced quantitatively by the white light digital speckle correlation method, the rock-coal deformation process in a specimen-testing machine system after the rockburst initiation has been studied . The localization band width is measured for the first time. The gradient plasticity constitutive relation is suggested by introducing the internal length parameter l to describe the deformation process after the rockburst starts. The analytical solution for the localization band width is derived under the condition of great stiffness and the small loading rate for the specimen-testing machine system. The comparison between the theoretical solution and the test results gives the material internal parameter l. The relation between the number and magnitude of the rockburst coincides well with the Gutenberg-Richter formula by studying the rockbursts ranging from magnitude 0.5~3.9 of 3 coal mines. The formula for the maximum magnitude is derived. This part of research makes it possible for the transformation from the 'comprehensive way' to the 'pertinent way' in the prediction and treatment of rockburst.The complete deformation-failure processes have been studied by the equivalent material: Two new similar coefficients for the simulation of the complete process of a rockburst have been suggested, the ratio E/λ for the description of the mechanism of a rockburst initiation and the internal length parameter l for thedescription of the material deformation after the initiation of the rockburst. A series of equivalent materials have been studied and made.The simulation experiments for the circular roadway rockburst has been carried out and the critical load for the rockburst initiation has been derived. The relative error for the theoretical solution compared with the test result is 5.7%. A rockburst of magnitude 3.2 occurring at Da'anshan coal mine was simulated in the laboratory and the rockburst occurring at the working face was reproduced. The succeeding mining activity was modeled. The mining work has finished safely with the application of the suggested way to the practice. This part of research results makes it possible for the transformation the major practical work in rockburst prevention and treatment from 'treatment' to 'prevention'.The fault-induced rockburst has been studied: initiation criterion has been set up;Theoretical research and simulation experiments for fault-induced rockburst are carried out;A stick-slip model has been given out;Some phenomena of this kind of rockburst have explained.