Abstract:

The distribution and propagation characteristics of water pressure in water-bearing crack under blasting load are of great significance to the study of the initial crack propagation mechanism in water-bearing fractured rock mass. Through the laboratory blasting experimental in concrete with water-bearing crack, the water pressure in water-bearing crack was measured during blasting, and its loading characteristics and propagation law were analyzed, while the effects of crack aperture and blasting charge quantity on water pressure were studied. The experimental results show that the time-history distribution of water pressure in water-bearing crack presents multi-peak fluctuation distribution. And the sources of water pressure include the blasting load directly transmitted through the water and indirectly transmitted through the concrete; the main source of load is different for different crack lengths. Under the same charging condition, the water pressure in water-bearing crack attenuates rapidly with increase of distance from the detonation source, and the water pressure at the same position in crack is approximately inversely proportional to the crack aperture. The energy spectrum of water hammer wave in water-bearing cracks is mainly concentrated in 7.8−62.5 kHz during laboratory explosion test of concrete with water-bearing crack, which is a high frequency signal. Meanwhile, the energy distribution trends to concentrate in the low frequency range with increase of distance from the detonation source. The energy distribution characteristics of water hammer wave are affected by charge and crack aperture, and the explosion induced by emulsion explosive of the equivalent 4.5 gTNT charge can generate water hammer wave with more abundant high frequency information in comparison with the equivalent 8.1 gTNT emulsion explosive charge. For the same blasting charge quantity, the peak energy distribution of the water hammer wave frequency band tends to move to the middle band with the increase of crack aperture.

Key words: explosion experiment, water-bearing crack, water pressure, propagation characteristic, aperture, energy distribution