Study On Failure And Fragmentation Characteristics Of Rock Under Static-Dynamic Coupling Loading

Many scholars engaging in research on rock mechanics have investigated the performances of rocks experiencing static load and dynamic load(including impact and disturbance loads, the same below), obtained many results, and made great progress on both rock mechanics theories and applications. However, those research results are mainly about cases that rock are only experienced static load or dynamic load. In fact, in engineering practice and nature, for example in deep mining, there are quite numbers of rock on the condition of high static stress or ground stress before they are experienced dynamic stress; but, there are few such research results. So, it is meaningful to investigate the characteristics of rock failure and fragmentation when static load and dynamic load are coupling applied on rock. According to the problem above, the author of this paper carried out the research deeply and systematically on the following failure/fragmentation characteristics of rock experiencing the static-dynamic coupling load on the basis of the experiment and theoretic analysis with the support of the National Natural Science Foundation of China.Firstly, by using of the Instron electro hydraulic and servo controlled material testing machine and adopting low-cycle-index fatigue loading method, the test of ID and 2D of red sandstone failure/fragmentation with medium strain rate under coupled static-dynamic loading is carried out to investigate the dynamic response and fragmentation characteristics, when red sandstone is experienced different horizontal stress and vertical stress on the condition of dynamic disturbance with different frequency and amplitude. The experimental and theoretical basis is provided for analyzing the pillar stability and rockburst in deep mining.Secondly, on the basis of the above experiment, mechanism on fragmentation and failure of rock is analyzed, and according to equivalent strain hypothesis, a new constitutive model of elastic - plastic damage is established, furthermore the law of releasing ratio of damage strain energy is discussed under the condition of different static stress. The stability of uniaxial static loading rock system are analyzed by the catastrophe theory, and the nonlinear dynamics model on uniaxial static loading rock system under dynamic disturbance is established. According to the catastrophe theory for impact buckling of static loading structures, a new catastrophe model for impact fragmentation of a rock system experiencing static loading has been established, it is found that the furcate collection denoting catastrophe maybe taking place is not only decided by mechanics of the system itself but also has something to do with exterior loading.Thirdly, by way of combining statistic damage model andviscoelastic model, constitutive model of rock experiencing coupled static-dynamic loading are established for the first time.Fourthly, using strain energy density concept to define a failure/fragmentation criterion of coupling static-dynamic loaded rock is proposed. On the basis of constitutive model of rock experiencing coupled static-dynamic loading, using mechanical model to represent the reduction of elasticity, occurrence of inelasticity deformation and effect of loading rate , is also proposed. According to mechanical model, the critical value of strain energy density of statically loaded rock coupling with dynamic loading is derived. The catastrophe theory is applied to analyze the process of dynamic fracture of static loaded rock by adding dynamic disturbance, the double cusp catastrophe model is proposed for internal crack growth in static loaded rock under dynamic disturbance, a new criterion for dynamic fracture of static loaded rock is given, the complicated process on crack propagation is described from the macro geometric aspects.Finally, a catastrophe model displaying the rockburst of the underground chamber under laminated buckling has been established, the evolvement law on underground chamber rockburst under laminated buckling is found under the condition of quasi-static pressure. And, a nonlinear dynamics model for underground chamber rockburst under laminated spallation buckling stimulated by dynamic disturbance is established for the first time. In addition, according to uniaxial static-dynamic coupling loading experiment, energy transform and consumption in failure/fragmentation of rock experiencing coupled static-dynamic loading are analyzed. On the basis of analysis above, the average ejecting velocity of rock fragments in rockburst is determined approximately, whose calculation method may be referred to the support design of rockburst tendency tunnel in deep mining.In short, the research of this dissertation, which is based on the frontal of the subject, applying the newest mathematical and mechanical methods and means to investigate the characteristics of rock failure and fragmentation, and the problem in engineering application, under the condition of static-dynamic coupling loaded rock system, is useful for both theory and practice, and in special for the developing of researsh on characteristics of deep rockmass.