| Drilling and blasting method is widely used in metal mining,tunnel excavation and other rock engineering.Because of its high efficiency,cylindrical charge blasting is widely used.It is of guiding significance to study the dynamic fracture behavior of rock under cylindrical charge blasting for rock engineering blasting design.However,it is difficult to observe the strain evolution and crack growth process in the process of super dynamic fracture of rock blasting,and the use of explosives is strictly controlled,so the indoor fine experiment can not be carried out.Therefore,the numerical simulation method is mostly used in the study of blasting process,while the physical experiment method is less.In this paper,the wire electric explosion technology is used to simulate the cylindrical charge blasting,and the strain field evolution and fracture process,the size of the blasting pit and the distribution of the fragmentation of the cement mortar specimen under the explosion load are studied experimentally.The main contents of this paper are as follows:(1)Firstly,the blasting scheme of metal straight wire parallel near free face is designed,the cement mortar experimental model specimen is prefabricated,and the near free face cylindrical charge electric blasting experiment is carried out.The results show that the method is safe and reliable,and can simulate the blasting of cylindrical charge.(2)The experiment of the influence of blasting energy on blasting effect is studied by using the above electric blasting method.The dynamic fracture process of the sample surface in the blasting process is observed by the ultra-high speed camera.The strain field evolution is studied by the digital speckle technique.The change rule of the size of the blasting fracture area with the charging voltage is also quantitatively analyzed.The distribution characteristics of the fragmentation are analyzed in detail with the R-R distribution.(3)Carry out blasting experiments of mortar samples under different burdens.The crack growth behavior and strain field evolution on the surface of the specimen are studied by combining the ultra-high speed camera and digital speckle technique.The influence of the burden on the parameters of the blasting funnel,such as volume,long and short axis,and perimeter is discussed.The distribution law of the fragmentation under different burdens is analyzed.(4)The blasting experiment of mortar specimen under uniaxial compression was carried out.The dynamic fracture behavior of mortar specimen surface under uniaxial static pressure and the influence of static stress on the size and block distribution of blasting pit were discussed.The research results of this paper provide theoretical support for engineering blasting design and an experimental means for indoor blasting research. |
