Study On Mechanism Of Rockburst Preparation And Development Based On The Least Energy Consumption Principle

The rockburst problems involving multi-fields such as mine exploitation, hydropower project, tunnel projects of railway and roadway and so on. It causes serious economic losses and casualties every year, and becomes a major disaster in the field of industrial safety. To be better understanded the mechanism of rockburst occurrence of hard-rock, the related problems of rockburst are studied in this dissertation. Based on theory analysis, and combining experiment research with numerical simulation, the mechanism of rockburst preparation and development is studied systematically, and the rockburst constitutive equations are established which can reflect the progress of rockburst preparation and development. Based on the analysises of rockburst influencing factors, the reasonable rockburst tendency indexes are put forward. The laws of AE activity of granite are obtained. The spatial distribution pattern of microseism and rockburst, and the internal relations of them are studied. The main research works included in the dissertation are as following:(1) The macro-failure characteristics and micro-damage characteristics of rockburst are analysised. And two type failure modes of rockmass from being forced to the finish of rockburst are initially determined. The studies of relative criteritions are carried out to describe the initial and finish of different failure mode quantitatively. The typical rockburst tendency hardrock granites were obtained from engineering site and they were prepared as standard specimen of 50mm in diameter and 100mm in length. Both conventional uniaxial & triaxial compression tests are conducted on MTS815.03 testing machine. The criterion of limit enery storage for rockburst occurrence is proposed through analyzing the relationship between ultimate strength and limit load for structural failure. The limit energy storage criterion and the structural failure criterion consists the necessary and sufficient condition of rockburst occurrence. The definition of rockburst and the mechanism of rockburst preparation and development are put forward.(2) The least energy consumption principle and its general procedures to establish development equation of internal variable are introduced in this dissertation. Damage evolution equation of the first type failure mode is estabilished using the least energy consumption principle from the view of energy. The rationablility of this damage evolution equation is proved by the data from granites testing. The constitutive of the stage of rockburst preparation is proposed following the establishing of constitutive of energy concentration stage from the view of energy. And the constitutive of the total progress of rockburst is proposed by simplifying the deformation state after the second failure mode to perfectly plastic state.(3) The critical region (damage area) for rockburst study is layed out based on the proposed rockburst constitutive of typical rockburst tendency hardrock. The relative analytical mode is put forward for the example of circle roadway. Influence factors of rockburst occurrence are studied under the isopiestic and anisocharic condition individually under the condition of meeting limit energy storage criterion. And related study is carried out for the purpose of determining the region and position of rockburst, the new index for rockburst tendency study is proposed. It is found that the energy storage mode during the rockburst preparation the enery storage mode without interface shear, through studying the two enery storage mode theoretically under anisocharic condition. The principles of rockburst prevention are put forward, and the effective rockburst prevention measures are laid out.(4) The related condition of theoriatical research for microseimic at present is expounded in detail. Acoustic emission test is carried out, and the laws of AE activity for granites are obtained. It is stated that the physical explanation for AE activity characteristic of every stage. The relation between AE activity and damage variable is studied.(5) The finite element program of the rockburst constitutive mode of rockburst tendency granites is compiled by using the famous FE software ABAQUS. It is obtained that the laws of stress accumulation and stress transition, the law of energy accumulation and energy transition, and the spatial distribution law of AE activity during the progress of rockburst preparation and development under the condition of different geometric shape roadway and different excavation method. The relation of the accumulation and transition of stress and energy with AE activity law is revealed, it provides theoretical basis for establishing the model of rockburst analysis and prediction.(6) Finally, the theoretical results are applied to actural engineering, e.g. the HongTouShan copper. According to the laboratory test, the constitutive equation are determined, the calculation model is built up and the related FEM program is used to predict the rockburst at level -647m.