| In the process of excavation in coal mine tunnel, very hard rock will be encountered inevitably. At this time, the boring machine will be very difficult to broken rock, not only reduce the tunneling efficiency, but also brings certain risk. By the method of drilling and blasting to excavate tunnel, not only can improve the driving efficiency, but also can reduce the cost effectively. So, it has very important theoretical significance and engineering practical significance to research the rock dynamic mechanical properties under dynamic loading and the rock damage law under shock loading.The rock dynamic characteristics are studied by the Split Hopkinson Press Bar (SHPB) of three kinds of sandstone specimen at different impact velocities and simulated the whole impact process by ANSYS/LSDYNA numerical simulation software. There are three kinds of damage mode of rock specimen which has obvious strain rate effect under impact load, they are strain damage, axial splitting tensile failure and crushing damage. The incident energy, reflected energy, transmitted energy, absorbed energy, critical absorbed energy and specimen internal energy have obvious strain rate effect and size effect, and the dynamic strength has significant correlation with the energy and strain rate. The stress transmit in incident variable cross section bar, incident bar, transmission bar have dispersion phenomenon, but the dispersion decreasing with the stress wave transmission.Through the analysis of theoretical calculation and numerical simulation of rock blasting, it can be obtained that the explosive stress wave load into the rock will be attenuated with the exponential law, blasting stress field distribution is symmetrical about the hole, wave surface is column in radial range, semi circle at both ends and the center of the semicircle is the center of both ends. Based on the explosive stress field distribution,put forward the formula of blasting funnel radius. |
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