Testing And Numerical Simulation On Explosion Strain Wave In Mortar Test Block

With the rapid development of economy in recent decades, urban construction and infrastructure construction developed by leaps and bounds. Blasting, as a new technology, has played a crucial role in bridges, tunnels, mines and urban demolition. However, the development of blasting engineering practice has lagged behind the theory. The study on explosive dynamics, which relating to the blasting theory, has been a difficult research topic.It is well known that explosion has been done instantly in rock. The explosion shock wave and high-temperature and high-pressure gas, which generated instantly, have a strong impact and crushing action on rock. The blasting mechanism is extremely complex, which is strict in test equipment and test technically, resulting in the test of explosions strain waves is rarely reported in the literature.The article was on the basis of previous experience which is summarized, and the explosion strain wave had been tested and numerical simulated in the mortar test block, which under the loading of explosion dynamic. It aimed at analyzing the strain waveform and propagation in rock media. The main contents were as follows:First, the testing technology of the blasting wave was studied, and the practical and reliable testing system and anti-jamming measures of explosion strain wave were proposed. It lay the foundation for the repeated and stable signal of blasting wave.Second, the explosion mechanism and mechanical properties of mortar concrete materials were studied. A reasonable way of pasting strain gages and installing strain brick was proposed. It reduced the interference of the interface effect to the test of stress wave.Third, the ultra-dynamic strain testing system was used to test explosion strain wave in mortar test block. The measured explosion strain waveforms were recognized and analysised. The results showed that the propagation of blasting wave mainly as a combined effect of stress wave and detonation gases. Wherein, the action time of the stress wave was about 10μs and the detonation gas action time was about 30μs. In the propagation of stress wave, the attenuation of compression wave was significantly greater than the tensile wave. At different distances from the center of the charge, the rising edge of blasting waves were basically the same, while in 150mm from the center of the charge, the falling edge increased and attenuation significantly.Fourth, according to the resulting waveform, the curves of radial and tangential strain rate over time were proposed from the different distance of the same point. The results showed that the strain rate of loading and unloading were at a magnitude of 106s-1. Among them, the peak of radial and tangential loading strain rate changes little, the peak of radial unloading strain rate attenuated significantly nearer away from the explosion source, while the peak of tangential unloading strain rate began attenuating farther away from the explosion source.Fifth, the fluid-structure coupling algorithm of ALE in ANSYS/LS-DYNA was used to take numerical simulation of the propagation of blasting wave in rocks. The results showed that the rock crushed by compression due to the effect of stress wave and the quasi-static of detonation gases at the beginning of an explosion. Most of the energy was consumed by the blast wave. With the propagation distance increasing, the blast wave was attenuated as stress wave, and the changes of energy leveled off. It was closer to the test results and engineering examples.