Experimental Study On Test And Identification Of Blast Wave In Adjacent Area To A Borehole In Concrete Model And Its Action

At present, seldom studies have been done on the detailed characteristics about essential parameters of the action course of blast wave, for the reason of its own complexity of explosion, the limitation of the test equipment and technology for testing the wave in adjacent area to a borehole in a concrete model, while destruction of the rock material results from the combination effect for the three kinds of blast stress acting. However, in recently, action course of blast wave still remains in determining the nature because it is difficult to do test to obtain signals of blast wave in adjacent area to a borehole, so studies are seldom done on the blast wave and rock damage evolution course with the separated stress. In order to solve the problems above, the author has done the systematical studies on the detailed characteristics of blast wave and rock damage evolution under blast wave in adjacent area to borehole combining with the two projects: the outstanding young teacher's support plan—Study on the technique of the efficient rock breakage by blasting in deep mining and prevention against relevant catastrophe (EYTP-2134), granted by Ministry of Education, and doctors fund subsidy subject of Ministry of Education "Recognition of blast wave signals and the dynamics process on it in adjacent area to a borehole". The main study results are as follows:Firstly, blast wave were tested successfully with characteristic of stabilizing, repeating, and high-efficiently in an all-round way for concrete through match studies on the dynamical measurement system and improving experimental technique for the first time. Comparing with other piezoelectricity or the pressure sensor, the systematic and experimental technique can exhibits the compressive and tensile stress, with non defect for the obtained data while the wave form is intact. The data reflected complicated action course of the blast wave truly. The experiment system and technique establish the solid experiment foundation for further quantitatively mechanism study and theoretical study for the rock blasting under blast wave in adjacent area to a borehole.Secondly, blast waves are recognized and divided into three sub areas, named first zone, second zone and third zone of stress wave action, based on analyzing the blast wave signals that had been tested in concrete and the theories of rock broken mechanism, etc. A rock broken course related to the each zone has been proposed for the first time. The damage process of the concrete is very complicated, in which occurs compressive, tensile by frist zone and second zone under the high strain rate with 10⁴/s as well as the quasi-static effect by third zone. On the space, the three kinds of blast wave act on the effective sphere of concrete at the same time. On time, they act on the measuring point sequentially and are the separate course, but. exist in inner link to the damage of the concrete.Thirdly, based on the reorganization for the blast wave under the condition of air decoupling charge, the detailed characteristics of the essential feature parameters in the separating area are obtained from different place in different coupling coefficient for the first time. Through analyzing essential features of the separating zones of blast wave, such as stress, loading strain rate and unloading rate, velocity and acceleration of particle,etc, the relationship among dynamics essential feature parameter of separating zones and the decoupling coefficient K and the distance from measuring point to bore hole is quantitatively established which have revealed deeply the detailed characteristics of propagating and mechanism of the instantaneous explosion wave in adjacent area to a borehole in a concrete model.Fourthly, combining with the others' former achievement, while comparing the wave form of a back wave tested from free face and contact explosion experiment to the wave form in the bore hole, the dividing action zones and the tested data of separated area of blast wave are verified correctly. The producing mechanism of the separating zones of blast wave is set up interrelated with detonation structure of explosive and the theory of rock breaking. First zone of blast wave in concrete is the acting result of explosion pressure in the wave front of explosion detonation, and third zone is the acting result of the detonation product with isentropic amorphous expansion flow after C-J interface of explosion detonation. And second zone of balst wave in concrete produces complicatedly, and may relate to the damage of the rock.Fifthly, the technology of time-frequency energy is used to analyze the blast wave for the first time, in which the signal of the separating blast wave zones has the characteristics of short time, frequency band complicatedness, the maldistribution of energy density and fast sudden change. From adaptability that the technology of linear and non-linear time frequency distribution analyze non-steady random limited signal of energy in short-term, optimum function of time-frequency distribution is selected to analyze dynamical strain of blast wave by the contrast of many kinds of analytical methods of time-frequency distribution appraising and calculating to the blast wave signal. And it establishes solid theory and application foundation for using time-frequency distribution to analyze instantaneous blast wave.Sixthly, based on the selected optimum function, Rihaczek distribution is used to analyze the blast waves tested near the cavity of concrete under the condition of radial air decoupling charge. Blast wave is recognized accurately at three-dimensional space of time-frequency energy, and is separated to dynamical strain energy density zones by Rihaczek distribution. Then the time-frequency energy distribute characteristic of every zone, dynamic strain energy of every zone and total energy are calculated. The dynamic change relation relationship between total energy or dynamic strain energy of every zone with decoupling coefficient K and the distance R from measuring point to bore hole are established. They deeply reveal the energy mechanism of the separating zones and detailed characteristic of the energy centre evolving on instantaneous explosion waves.Finally, acoustic wave measurement technology is used to study the concrete damage after exploded and the damage evolving mechanism of structure which interrelated with the essential feature parameters and energy in the separating area is set up. Dynamic strain energy threshold E_cri related to damaging threshold value D_cri is put forward as energy criterion of rock damage. By comparing with E_cri and the dynamical strain energy of separating zones, it can be judged whether new cracks are produced. The function of first zone of blast wave action reflects in producing new cracks and expanding the cracks mainly. The function of second zone and third zone action is to expand the new cracks, and stress and energy centralized in damaging boundary.The above main conclusions obtained in the project have significant value both in theoretical investigation and engineering application with discipline of blasting engineering, defense engineering, constitutive relation of rock body, the characteristic of the seismic wave etc., and build a solid experiment foundation, a theoretical and technological basis for studying action characteristics of instantaneous blast wave and damage evolution of rock related blast wave in adjacent area to a borehole in concrete models...